draft-ietf-payload-melpe-06.txt   rfc8130.txt 
Payload Working Group Victor Demjanenko Internet Engineering Task Force (IETF) V. Demjanenko
Internet-Draft David Satterlee Request for Comments: 8130 D. Satterlee
Intended Status: Standards Track VOCAL Technologies, Ltd. Category: Standards Track VOCAL Technologies, Ltd.
Expires: August 11, 2017 February 7, 2017 ISSN: 2070-1721 March 2017
RTP Payload Format for MELPe Codec RTP Payload Format
draft-ietf-payload-melpe-06 for the Mixed Excitation Linear Prediction Enhanced (MELPe) Codec
Status of this Memo Abstract
This document describes the RTP payload format for the Mixed
Excitation Linear Prediction Enhanced (MELPe) speech coder. MELPe's
three different speech encoding rates and sample frame sizes are
supported. Comfort noise procedures and packet loss concealment are
described in detail.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8130.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
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Abstract
This document describes the RTP payload format for the Mixed
Excitation Linear Prediction Enhanced (MELPe) speech coder. MELPe's
three different speech encoding rates and sample frames sizes are
supported. Comfort noise procedures and packet loss concealment are
detailed.
Table of Contents Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
1.1 Conventions, Definitions and Acronyms . . . . . . . . . . . 3 1.1. Conventions ................................................2
2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background ......................................................3
3 Payload Format . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Payload Format ..................................................4
3.1 MELPe Bitstream Definition . . . . . . . . . . . . . . . . 5 3.1. MELPe Bitstream Definitions ................................5
3.1.1 2400 bps Bitstream Structure . . . . . . . . . . . . . . 6 3.1.1. 2400 bps Bitstream Structure ........................6
3.1.2 1200 bps Bitstream Structure . . . . . . . . . . . . . . 8 3.1.2. 1200 bps Bitstream Structure ........................9
3.1.3 600 bps Bitstream Structure . . . . . . . . . . . . . . 11 3.1.3. 600 bps Bitstream Structure ........................13
3.2 MELPe Comfort Noise Bitstream Definition . . . . . . . . . 15 3.2. MELPe Comfort Noise Bitstream Definition ..................18
3.3 Multiple MELPe frames in a RTP packet . . . . . . . . . . . 17 3.3. Multiple MELPe Frames in an RTP Packet ....................20
3.4 Congestion Control Considerations . . . . . . . . . . . . . 19 3.4. Congestion Control Considerations .........................21
4 Payload Format Parameters . . . . . . . . . . . . . . . . . . . 19 4. Payload Format Parameters ......................................22
4.1 Media Type Definition . . . . . . . . . . . . . . . . . . . 20 4.1. Media Type Definitions ....................................22
4.2 Mapping to SDP . . . . . . . . . . . . . . . . . . . . . . 23 4.2. Mapping to SDP ............................................23
4.3 Declarative SDP Considerations . . . . . . . . . . . . . . 24 4.3. Declarative SDP Considerations ............................25
4.4 Offer/Answer SDP Considerations . . . . . . . . . . . . . . 24 4.4. Offer/Answer SDP Considerations ...........................25
5 Discontinious Transmission . . . . . . . . . . . . . . . . . . 25 5. Discontinuous Transmissions ....................................26
6 Packet Loss Concealment . . . . . . . . . . . . . . . . . . . . 25 6. Packet Loss Concealment ........................................26
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 27 7. IANA Considerations ............................................26
8 Security Considerations . . . . . . . . . . . . . . . . . . . . 27 8. Security Considerations ........................................27
9 RFC Editor Considerations . . . . . . . . . . . . . . . . . . . 27 9. References .....................................................27
10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 9.1. Normative References ......................................27
10.1 Normative References . . . . . . . . . . . . . . . . . . . 27 9.2. Informative References ....................................29
10.2 Informative References . . . . . . . . . . . . . . . . . . 29 Authors' Addresses ................................................30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
1 Introduction 1. Introduction
This document describes how compressed MELPe speech as produced by This document describes how compressed Mixed Excitation Linear
the MELPe codec may be formatted for use as an RTP payload. Details Prediction Enhanced (MELPe) speech as produced by the MELPe codec
are provided to packetize the three different codec bit-rate data may be formatted for use as an RTP payload. Details are provided to
frames (2400, 1200, and 600) into RTP packets. The sender may send packetize the three different codec bitrate data frames (2400, 1200,
one or more codec data frames per packet, depending on the and 600) into RTP packets. The sender may send one or more codec
application scenario or based on the transport network condition, data frames per packet, depending on the application scenario or
bandwidth restriction, delay requirements and packet-loss tolerance. based on transport network conditions, bandwidth restrictions, delay
requirements, and packet loss tolerance.
1.1 Conventions, Definitions and Acronyms 1.1. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Best current practices for writing RTP payload format [RFC2736] were
followed.
2 Background Best current practices for writing an RTP payload format
specification were followed [RFC2736].
2. Background
The MELP speech coder was developed by the US military as an upgrade The MELP speech coder was developed by the US military as an upgrade
from LPC-based CELP standard vocoder for low bit-rate communications from the LPC-based CELP standard vocoder for low-bitrate
[MELP]. MELP was further enhanced and subsequently adopted by NATO communications [MELP]. ("LPC" stands for "Linear-Predictive Coding",
as MELPe for use by its members and Partnership for Peace countries and "CELP" stands for "Code-Excited Linear Prediction".) MELP was
for military and other governmental communications [MELPE]. The MELP further enhanced and subsequently adopted by NATO as MELPe for use by
speech coder algorithm developed by Atlanta Signal Processing (ASPI), its members and Partnership for Peace countries for military and
Texas Instruments (TI), SignalCom (now Microsoft) and Thales other governmental communications [MELPE]. The MELP speech coder
Communications with noise preprocessor contributions from AT&T under algorithm was developed by Atlanta Signal Processing (ASPI), Texas
contract with NSA/DOD as international NATO Standard STANAG 4591. Instruments (TI), SignalCom (now Microsoft), and Thales
Communications, with noise preprocessor contributions from AT&T,
under contract with NSA/DOD as international NATO Standard
STANAG 4591 [MELPE].
Commercial/civilian applications have arisen because of the low bit- Commercial/civilian applications have arisen because of the
rate property of MELPe with its (relatively) high intelligibility. low-bitrate property of MELPe with its (relatively) high
As such MELPe is being used in a variety of wired and radio intelligibility. As such, MELPe is being used in a variety of wired
communications systems. VoIP/SIP systems need to transport MELPe and radio communications systems. Voice over IP (VoIP) / SIP systems
without decoding and re-encoding in order to preserve its need to transport MELPe without decoding and re-encoding in order to
intelligibility. Hence it is desirable and necessary to define the preserve its intelligibility. Hence, it is desirable and necessary
proper payload formatting and use conventions of MELPe in RTP to define the proper payload formatting and use conventions of MELPe
payloads. in RTP payloads.
The MELPe codec [MELPE] supports three different vocoder bit rates; The MELPe codec [MELPE] supports three different vocoder bitrates:
2400, 1200, and 600 bps. The basic 2400 bps bit-rate vocoder uses a 2400, 1200, and 600 bps. The basic 2400 bps bitrate vocoder uses a
22.5 ms frame of speech consisting of 180 8000 Hz, 16-bit speech 22.5 ms frame of speech consisting of 180 8000-Hz, 16-bit speech
samples. The 1200 and 600 bps bit-rate vocoders uses respectively samples. The 1200 and 600 bps bitrate vocoders each use three and
three and four 22.5 ms frames of speech each. These reduced bit-rate four 22.5 ms frames of speech, respectively. These reduced-bitrate
vocoders internally use multiple 2400 bps parameter sets with further vocoders internally use multiple 2400 bps parameter sets with further
processing to strategically remove redundancy. The payload sizes for processing to strategically remove redundancy. The payload sizes for
each of the bitrates are 54, 81, and 54 bits respectively for the each of the bitrates are 54, 81, and 54 bits for the 2400, 1200, and
2400, 1200, and 600 bps frames. Dynamic bit-rate switching is 600 bps frames, respectively. Dynamic bitrate switching is permitted
permitted but only if supported by both endpoints. but only if supported by both endpoints.
The MELPe algorithm distinguishes between voiced and un-voiced speech The MELPe algorithm distinguishes between voiced and unvoiced speech
and encodes each differently. Unvoiced speech can be coded with and encodes each differently. Unvoiced speech can be coded with
fewer information bits for the same quality. Forward error fewer information bits for the same quality. Forward error
correction (FEC) is applied to the 2400 bps codec unvoiced speech for correction (FEC) is applied to the 2400 bps codec unvoiced speech for
better protection of the subtle differences in signal reconstruction. better protection of the subtle differences in signal reconstruction.
The lower bit-rate coders do not allocate any bits for FEC and rely The lower-bitrate coders do not allocate any bits for FEC and rely on
on strong error protection and correction in the communications strong error protection and correction in the communications channel.
channel.
Comfort noise handling for MELPe follows the procedures in SCIP-210 Comfort noise handling for MELPe follows the procedures in Appendix B
Appendix B [SCIP210]. After VAD no longer indicates the presence of of SCIP-210 [SCIP210]. After Voice Activity Detection (VAD)
speech/voice, a grace period of a minimum of two comfort noise no longer indicates the presence of speech/voice, a minimum of two
vocoder fames are to be transmitted. The contents of the comfort comfort noise vocoder frames (serving as a grace period) are to be
noise frames is described in the next section. transmitted. The contents of the comfort noise frames are described
in the next section.
Packet loss concealment (PLC) exploits the FEC (and more precisely, Packet loss concealment (PLC) exploits the FEC (and, more precisely,
any combination of two set bits in the pitch/voicing parameter) of any combination of two set bits in the pitch/voicing parameter) of
the 2400 bps speech coder. The pitch/voicing parameter has a sparse the 2400 bps speech coder. The pitch/voicing parameter has a sparse
set of permitted values. A value of zero indicates a non-voiced set of permitted values. A value of zero indicates a non-voiced
frame. At least three bits are set for all valid pitch parameters. frame. At least three bits are set for all valid pitch parameters.
The PLC erasure indication utilizes any of the two bit set The PLC erasure indication utilizes any errored/erasure encodings of
errored/erasure encodings of a non-voiced frame as will be described the pitch/voicing parameter with exactly two set bits, as described
infra. below.
3 Payload Format 3. Payload Format
The MELPe codec uses 22.5, 67.5 or 90 ms frames with a sampling rate The MELPe codec uses 22.5, 67.5, or 90 ms frames with a sampling rate
clock of 8 kHz, so the RTP timestamp MUST be in units of 1/8000 of a clock of 8 kHz, so the RTP timestamp MUST be in units of 1/8000 of a
second. second.
The RTP payload for MELPe has the format shown in Figure 1. No The RTP payload for MELPe has the format shown in Figure 1. No
additional header specific to this payload format is needed. This additional header specific to this payload format is needed. This
format is intended for the situations where the sender and the format is intended for situations where the sender and the receiver
receiver send one or more codec data frames per packet. send one or more codec data frames per packet.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP Header | | RTP Header |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| | | |
+ one or more frames of MELPe | + one or more frames of MELPe |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 - Packet format diagram Figure 1: Packet Format Diagram
The RTP header of the packetized encoded MELPe speech has the The RTP header of the packetized encoded MELPe speech has the
expected values as described in [RFC3550]. The usage of M bit SHOULD expected values as described in [RFC3550]. The usage of the M bit
be as specified in the applicable RTP profile, for example, RFC 3551 SHOULD be as specified in the applicable RTP profile -- for example,
[RFC3551], where [RFC3551] specifies that if the sender does not [RFC3551], where [RFC3551] specifies that if the sender does not
suppress silence (i.e., sends a frame on every frame interval), the M suppress silence (i.e., sends a frame on every frame interval), the
bit will always be zero. When more then one codec data frame is M bit will always be zero. When more than one codec data frame is
present in a single RTP packet, the timestamp is, as always, that of present in a single RTP packet, the timestamp is, as always, that of
the oldest data frame represented in the RTP packet. the oldest data frame represented in the RTP packet.
The assignment of an RTP payload type for this new packet format is The assignment of an RTP payload type for this new packet format is
outside the scope of this document, and will not be specified here. outside the scope of this document and will not be specified here.
It is expected that the RTP profile for a particular class of It is expected that the RTP profile for a particular class of
applications will assign a payload type for this encoding, or if that applications will assign a payload type for this encoding, or if that
is not done, then a payload type in the dynamic range shall be chosen is not done, then a payload type in the dynamic range shall be chosen
by the sender. by the sender.
3.1 MELPe Bitstream Definition 3.1. MELPe Bitstream Definitions
The total number of bits used to describe one frame of 2400 bps The total number of bits used to describe one frame of 2400 bps
speech is 54, which fits in 7 octets (with two unused bits). For the speech is 54, which fits in 7 octets (with two unused bits). For
1200 bps speech the total number of bits used is 81, which fits in 11 1200 bps speech, the total number of bits used is 81, which fits in
octets (with seven unused bits). For the 600 bps speech the total 11 octets (with seven unused bits). For 600 bps speech, the total
number of bits used is 54, which fits in 7 octets (with two unused number of bits used is 54, which fits in 7 octets (with two unused
bits). Unused bits, shown below as RSVA, RSVB, etc., are coded as bits). Unused bits, shown below as RSVA, RSVB, etc., are coded as
described in 3.3 in support of dynamic bit-rate switching. described in Section 3.3 in support of dynamic bitrate switching.
In the MELPe bitstream definition, the most significant bits are In the MELPe bitstream definitions, the most significant bits are
considered priority bits. The intention was that these bits receive considered priority bits. The intention was that these bits receive
greater protection in the underlying communications channel. For IP greater protection in the underlying communications channel. For IP
networks, such additional protection is irrelevant. However, for networks, such additional protection is irrelevant. However, for the
convenience of interoperable gateway devices, the bitstreams will be convenience of interoperable gateway devices, the bitstreams will be
presented identically in IP networks. presented identically in IP networks.
3.1.1 2400 bps Bitstream Structure 3.1.1. 2400 bps Bitstream Structure
According to Table 3 of [MELPE], the 2400 bit/s MELPe bit
transmission order (bit priority is not shown for clarity) is the
following:
+--------+-------------+-------------+ According to Table 3 of [MELPE], the 2400 bps MELPe bit transmission
| Bit | Voiced | Unvoiced | order (for clarity, the bit priority is not shown) is as follows:
+--------+-------------+-------------+
| B_01 | g20 | g20 |
| B_02 | BP0 | FEC10 |
| B_03 | P0 | P0 |
| B_04 | LSF20 | LSF20 |
| B_05 | LSF30 | LSF30 |
| B_06 | g23 | g23 |
| B_07 | g24 | g24 |
| B_08 | LSF35 | LSF35 |
+--------+-------------+-------------+
| B_09 | g21 | g21 |
| B_10 | g22 | g22 |
| B_11 | P4 | P4 |
| B_12 | LSF34 | LSF34 |
| B_13 | P5 | P5 |
| B_14 | P1 | P1 |
| B_15 | P2 | P2 |
| B_16 | LSF40 | LSF40 |
+--------+-------------+-------------+
| B_17 | P6 | P6 |
| B_18 | LSF10 | LSF10 |
| B_19 | LSF16 | LSF16 |
| B_20 | LSF45 | LSF45 |
| B_21 | P3 | P3 |
| B_22 | LSF15 | LSF15 |
| B_23 | LSF14 | LSF14 |
| B_24 | LSF25 | LSF25 |
+--------+-------------+-------------+
| B_25 | BP3 | FEC13 |
| B_26 | LSF13 | LSF13 |
| B_27 | LSF12 | LSF12 |
| B_28 | LSF24 | LSF24 |
| B_29 | LSF44 | LSF44 |
| B_30 | FM0 | FEC40 |
| B_31 | LSF11 | LSF11 |
| B_32 | LSF23 | LSF23 |
+--------+-------------+-------------+
| B_33 | FM7 | FEC22 |
| B_34 | FM6 | FEC21 |
| B_35 | FM5 | FEC20 |
| B_36 | g11 | g11 |
| B_37 | g10 | g10 |
| B_38 | BP2 | FEC12 |
| B_39 | BP1 | FEC11 |
| B_40 | LSF21 | LSF21 |
+--------+-------------+-------------+
| B_41 | LSF33 | LSF33 |
| B_42 | LSF22 | LSF22 |
| B_43 | LSF32 | LSF32 |
| B_44 | LSF31 | LSF31 |
| B_45 | LSF43 | LSF43 |
| B_46 | LSF42 | LSF42 |
| B_47 | AF | FEC42 |
| B_48 | LSF41 | LSF41 |
+--------+-------------+-------------+
| B_49 | FM4 | FEC32 |
| B_50 | FM3 | FEC31 |
| B_51 | FM2 | FEC30 |
| B_52 | FM1 | FEC41 |
| B_53 | g12 | g12 |
| B_54 | SYNC | SYNC |
+--------+-------------+-------------+
NOTES: +--------+-------------+-------------+
g = Gain | Bit | Voiced | Unvoiced |
BP = Bandpass Voicing +--------+-------------+-------------+
P = Pitch/Voicing | B_01 | g20 | g20 |
LSF = Line Spectral Frequencies | B_02 | BP0 | FEC10 |
FEC = Forward Error Correction Parity Bits | B_03 | P0 | P0 |
FM = Fourier Magnitudes | B_04 | LSF20 | LSF20 |
AF = Aperiodic Flag | B_05 | LSF30 | LSF30 |
| B_06 | g23 | g23 |
| B_07 | g24 | g24 |
| B_08 | LSF35 | LSF35 |
+--------+-------------+-------------+
| B_09 | g21 | g21 |
| B_10 | g22 | g22 |
| B_11 | P4 | P4 |
| B_12 | LSF34 | LSF34 |
| B_13 | P5 | P5 |
| B_14 | P1 | P1 |
| B_15 | P2 | P2 |
| B_16 | LSF40 | LSF40 |
+--------+-------------+-------------+
| B_17 | P6 | P6 |
| B_18 | LSF10 | LSF10 |
| B_19 | LSF16 | LSF16 |
| B_20 | LSF45 | LSF45 |
| B_21 | P3 | P3 |
| B_22 | LSF15 | LSF15 |
| B_23 | LSF14 | LSF14 |
| B_24 | LSF25 | LSF25 |
+--------+-------------+-------------+
| B_25 | BP3 | FEC13 |
| B_26 | LSF13 | LSF13 |
| B_27 | LSF12 | LSF12 |
| B_28 | LSF24 | LSF24 |
| B_29 | LSF44 | LSF44 |
| B_30 | FM0 | FEC40 |
| B_31 | LSF11 | LSF11 |
| B_32 | LSF23 | LSF23 |
+--------+-------------+-------------+
| B_33 | FM7 | FEC22 |
| B_34 | FM6 | FEC21 |
| B_35 | FM5 | FEC20 |
| B_36 | g11 | g11 |
| B_37 | g10 | g10 |
| B_38 | BP2 | FEC12 |
| B_39 | BP1 | FEC11 |
| B_40 | LSF21 | LSF21 |
+--------+-------------+-------------+
| B_41 | LSF33 | LSF33 |
| B_42 | LSF22 | LSF22 |
| B_43 | LSF32 | LSF32 |
| B_44 | LSF31 | LSF31 |
| B_45 | LSF43 | LSF43 |
| B_46 | LSF42 | LSF42 |
| B_47 | AF | FEC42 |
| B_48 | LSF41 | LSF41 |
+--------+-------------+-------------+
| B_49 | FM4 | FEC32 |
| B_50 | FM3 | FEC31 |
| B_51 | FM2 | FEC30 |
| B_52 | FM1 | FEC41 |
| B_53 | g12 | g12 |
| B_54 | SYNC | SYNC |
+--------+-------------+-------------+
B_01 = least significant bit of data set Notes:
g = Gain
BP = Bandpass Voicing
P = Pitch/Voicing
LSF = Line Spectral Frequencies
FEC = Forward Error Correction Parity Bits
FM = Fourier Magnitudes
AF = Aperiodic Flag
B_01 = least significant bit of data set
Table 3.1 - The bitstream definition for MELPe 2400 bps. Table 1: Bitstream Definition for MELPe 2400 bps
The 2400 bps MELPe RTP payload is constructed as per Figure 2. Note The 2400 bps MELPe RTP payload is constructed as per Figure 2. Note
that bit B_01 is placed in the LSB of the first byte with all other that bit B_01 is placed in the least significant bit (LSB) of the
bits in sequence. When filling octets, the least significant bits of first byte with all other bits in sequence. When filling octets, the
the seventh octet are filled with bits B_49 to B_54 respectively. least significant bits of the seventh octet are filled with bits B_49
to B_54, respectively.
MSB LSB MSB LSB
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 | | B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 | | B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 | | B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 | | B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 | | B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 | | B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 | | RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
Figure 2 - Packed MELPe 2400 bps payload octets. Figure 2: Packed MELPe 2400 bps Payload Octets
3.1.2 1200 bps Bitstream Structure 3.1.2. 1200 bps Bitstream Structure
According to Tables D9a and D9b of [MELPE], the 1200 bit/s MELPe bit According to Tables D-9a and D-9b of [MELPE], the 1200 bps MELPe bit
transmission order is the following: transmission order is as follows:
+--------+-------------+-------------+ +--------+-------------+-------------+
| Bit | Modes 1-4 | Mode 5 | | Bit | Modes 1-4 | Mode 5 |
| | (Voiced) | (Unvoiced) | | | (Voiced) | (Unvoiced) |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_01 | Syn | Syn | | B_01 | Syn | Syn |
| B_02 | Pitch&UV0 | Pitch&UV0 | | B_02 | Pitch&UV0 | Pitch&UV0 |
| B_03 | Pitch&UV1 | Pitch&UV1 | | B_03 | Pitch&UV1 | Pitch&UV1 |
| B_04 | Pitch&UV2 | Pitch&UV2 | | B_04 | Pitch&UV2 | Pitch&UV2 |
| B_05 | Pitch&UV3 | Pitch&UV3 | | B_05 | Pitch&UV3 | Pitch&UV3 |
| B_06 | Pitch&UV4 | Pitch&UV4 | | B_06 | Pitch&UV4 | Pitch&UV4 |
| B_07 | Pitch&UV5 | Pitch&UV5 | | B_07 | Pitch&UV5 | Pitch&UV5 |
| B_08 | Pitch&UV6 | Pitch&UV6 | | B_08 | Pitch&UV6 | Pitch&UV6 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_09 | Pitch&UV7 | Pitch&UV7 | | B_09 | Pitch&UV7 | Pitch&UV7 |
| B_10 | Pitch&UV8 | Pitch&UV8 | | B_10 | Pitch&UV8 | Pitch&UV8 |
| B_11 | Pitch&UV9 | Pitch&UV9 | | B_11 | Pitch&UV9 | Pitch&UV9 |
| B_12 | Pitch&UV10 | Pitch&UV10 | | B_12 | Pitch&UV10 | Pitch&UV10 |
| B_13 | Pitch&UV11 | Pitch&UV11 | | B_13 | Pitch&UV11 | Pitch&UV11 |
| B_14 | LSP0 | LSP0 | | B_14 | LSP0 | LSP0 |
| B_15 | LSP1 | LSP1 | | B_15 | LSP1 | LSP1 |
| B_16 | LSP2 | LSP2 | | B_16 | LSP2 | LSP2 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_17 | LSP3 | LSP3 | | B_17 | LSP3 | LSP3 |
| B_18 | LSP4 | LSP4 | | B_18 | LSP4 | LSP4 |
| B_19 | LSP5 | LSP5 | | B_19 | LSP5 | LSP5 |
| B_20 | LSP6 | LSP6 | | B_20 | LSP6 | LSP6 |
| B_21 | LSP7 | LSP7 | | B_21 | LSP7 | LSP7 |
| B_22 | LSP8 | LSP8 | | B_22 | LSP8 | LSP8 |
| B_23 | LSP9 | LSP9 | | B_23 | LSP9 | LSP9 |
| B_24 | LSP10 | LSP10 | | B_24 | LSP10 | LSP10 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_25 | LSP11 | LSP11 | | B_25 | LSP11 | LSP11 |
| B_26 | LSP12 | LSP12 | | B_26 | LSP12 | LSP12 |
| B_27 | LSP13 | LSP13 | | B_27 | LSP13 | LSP13 |
| B_28 | LSP14 | LSP14 | | B_28 | LSP14 | LSP14 |
| B_29 | LSP15 | LSP15 | | B_29 | LSP15 | LSP15 |
| B_30 | LSP16 | LSP16 | | B_30 | LSP16 | LSP16 |
| B_31 | LSP17 | LSP17 | | B_31 | LSP17 | LSP17 |
| B_32 | LSP18 | LSP18 | | B_32 | LSP18 | LSP18 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_33 | LSP19 | LSP19 | | B_33 | LSP19 | LSP19 |
| B_34 | LSP20 | LSP20 | | B_34 | LSP20 | LSP20 |
| B_35 | LSP21 | LSP21 | | B_35 | LSP21 | LSP21 |
| B_36 | LSP22 | LSP22 | | B_36 | LSP22 | LSP22 |
| B_37 | LSP23 | LSP23 | | B_37 | LSP23 | LSP23 |
| B_38 | LSP24 | LSP24 | | B_38 | LSP24 | LSP24 |
| B_39 | LSP25 | LSP25 | | B_39 | LSP25 | LSP25 |
| B_40 | LSP26 | LSP26 | | B_40 | LSP26 | LSP26 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_41 | LSP27 | GAIN0 | | B_41 | LSP27 | GAIN0 |
| B_42 | LSP28 | GAIN1 | | B_42 | LSP28 | GAIN1 |
| B_43 | LSP29 | GAIN2 | | B_43 | LSP29 | GAIN2 |
| B_44 | LSP30 | GAIN3 | | B_44 | LSP30 | GAIN3 |
| B_45 | LSP31 | GAIN4 | | B_45 | LSP31 | GAIN4 |
| B_46 | LSP32 | GAIN5 | | B_46 | LSP32 | GAIN5 |
| B_47 | LSP33 | GAIN6 | | B_47 | LSP33 | GAIN6 |
| B_48 | LSP34 | GAIN7 | | B_48 | LSP34 | GAIN7 |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_49 | LSP35 | GAIN8 | | B_49 | LSP35 | GAIN8 |
| B_50 | LSP36 | GAIN9 | | B_50 | LSP36 | GAIN9 |
| B_51 | LSP37 | | | B_51 | LSP37 | |
| B_52 | LSP38 | | | B_52 | LSP38 | |
| B_53 | LSP39 | | | B_53 | LSP39 | |
| B_54 | LSP40 | | | B_54 | LSP40 | |
| B_55 | LSP41 | | | B_55 | LSP41 | |
| B_56 | LSP42 | | | B_56 | LSP42 | |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_57 | GAIN0 | | | B_57 | GAIN0 | |
| B_58 | GAIN1 | | | B_58 | GAIN1 | |
| B_59 | GAIN2 | | | B_59 | GAIN2 | |
| B_60 | GAIN3 | | | B_60 | GAIN3 | |
| B_61 | GAIN4 | | | B_61 | GAIN4 | |
| B_62 | GAIN5 | | | B_62 | GAIN5 | |
| B_63 | GAIN6 | | | B_63 | GAIN6 | |
| B_64 | GAIN7 | | | B_64 | GAIN7 | |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_65 | GAIN8 | | | B_65 | GAIN8 | |
| B_66 | GAIN9 | | | B_66 | GAIN9 | |
| B_67 | BP0 | | | B_67 | BP0 | |
| B_68 | BP1 | | | B_68 | BP1 | |
| B_69 | BP2 | | | B_69 | BP2 | |
| B_70 | BP3 | | | B_70 | BP3 | |
| B_71 | BP4 | | | B_71 | BP4 | |
| B_72 | BP5 | | | B_72 | BP5 | |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_73 | JITTER | | | B_73 | JITTER | |
| B_74 | FS0 | | | B_74 | FS0 | |
| B_75 | FS1 | | | B_75 | FS1 | |
| B_76 | FS2 | | | B_76 | FS2 | |
| B_77 | FS3 | | | B_77 | FS3 | |
| B_78 | FS4 | | | B_78 | FS4 | |
| B_79 | FS5 | | | B_79 | FS5 | |
| B_80 | FS6 | | | B_80 | FS6 | |
+--------+-------------+-------------+ +--------+-------------+-------------+
| B_81 | FS7 | | | B_81 | FS7 | |
+--------+-------------+-------------+ +--------+-------------+-------------+
NOTES: Notes:
BP = Band pass voicing BP = Bandpass voicing
FS = Fourier magnitudes FS = Fourier magnitudes
LSP = Line Spectral Pair
Pitch&UV = Pitch/voicing
GAIN = Gain
JITTER = Jitter
Table 3.2 - The bitstream definition for MELPe 1200 bps. Table 2: Bitstream Definition for MELPe 1200 bps
The 1200 bps MELPe RTP payload is constructed as per Figure 3. Note The 1200 bps MELPe RTP payload is constructed as per Figure 3. Note
that bit B_01 is placed in the LSB of the first byte with all other that bit B_01 is placed in the LSB of the first byte with all other
bits in sequence. When filling octets, the least significant bit of bits in sequence. When filling octets, the least significant bit of
the eleventh octet is filled with bit B_81. the eleventh octet is filled with bit B_81.
MSB LSB MSB LSB
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 | | B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 | | B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 | | B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 | | B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 | | B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 | | B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_56 | B_55 | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 | | B_56 | B_55 | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_64 | B_63 | B_62 | B_61 | B_60 | B_59 | B_58 | B_57 | | B_64 | B_63 | B_62 | B_61 | B_60 | B_59 | B_58 | B_57 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_72 | B_71 | B_70 | B_69 | B_68 | B_67 | B_66 | B_65 | | B_72 | B_71 | B_70 | B_69 | B_68 | B_67 | B_66 | B_65 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_80 | B_79 | B_78 | B_77 | B_76 | B_75 | B_74 | B_73 | | B_80 | B_79 | B_78 | B_77 | B_76 | B_75 | B_74 | B_73 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| RSVA | RSVB | RSVC | RSV0 | RSV0 | RSV0 | RSV0 | B_81 | | RSVA | RSVB | RSVC | RSV0 | RSV0 | RSV0 | RSV0 | B_81 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
Figure 3 - Packed MELPe 1200 bps payload octets. Figure 3: Packed MELPe 1200 bps Payload Octets
3.1.3 600 bps Bitstream Structure 3.1.3. 600 bps Bitstream Structure
According to Tables M-11 to M-16 of [MELPE], the 600 bit/s MELPe bit According to Tables M-11 to M-16 of [MELPE], the 600 bps MELPe bit
transmission order (bit priority is not shown for clarity) is the transmission order (for clarity, the bit priority is not shown) is as
following: follows:
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
| Bit | Mode 1 | Mode 2 | Mode 3 | | Bit | Mode 1 | Mode 2 | Mode 3 |
| | (Voiced) | (voiced) | (voiced) | | | (Voiced) | (voiced) | (voiced) |
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
| B_01 | Voicing (4) | Voicing (4) | Voicing (4) | | B_01 | Voicing (4) | Voicing (4) | Voicing (4) |
| B_02 | Voicing (3) | Voicing (3) | Voicing (3) | | B_02 | Voicing (3) | Voicing (3) | Voicing (3) |
| B_03 | Voicing (2) | Voicing (2) | Voicing (2) | | B_03 | Voicing (2) | Voicing (2) | Voicing (2) |
| B_04 | Voicing (1) | Voicing (1) | Voicing (1) | | B_04 | Voicing (1) | Voicing (1) | Voicing (1) |
| B_05 | Voicing (0) | Voicing (0) | Voicing (0) | | B_05 | Voicing (0) | Voicing (0) | Voicing (0) |
skipping to change at page 13, line 10 skipping to change at page 14, line 31
| B_48 | GAIN1 (6) | GAIN1 (6) | GAIN2 (0) | | B_48 | GAIN1 (6) | GAIN1 (6) | GAIN2 (0) |
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
| B_49 | GAIN1 (5) | GAIN1 (5) | GAIN1 (5) | | B_49 | GAIN1 (5) | GAIN1 (5) | GAIN1 (5) |
| B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) | | B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) |
| B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) | | B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) |
| B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) | | B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) |
| B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) | | B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) |
| B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) | | B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) |
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
Table 3.3a - The bitstream definition for MELPe 600 bps (part 1 of Table 3: Bitstream Definition for MELPe 600 bps (Part 1 of 2)
2).
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
| Bit | Mode 4 | Mode 5 | Mode 6 | | Bit | Mode 4 | Mode 5 | Mode 6 |
| | (voiced) | (voiced) | (voiced) | | | (voiced) | (voiced) | (voiced) |
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
| B_01 | Voicing (4) | Voicing (4) | Voicing (4) | | B_01 | Voicing (4) | Voicing (4) | Voicing (4) |
| B_02 | Voicing (3) | Voicing (3) | Voicing (3) | | B_02 | Voicing (3) | Voicing (3) | Voicing (3) |
| B_03 | Voicing (2) | Voicing (2) | Voicing (2) | | B_03 | Voicing (2) | Voicing (2) | Voicing (2) |
| B_04 | Voicing (1) | Voicing (1) | Voicing (1) | | B_04 | Voicing (1) | Voicing (1) | Voicing (1) |
| B_05 | Voicing (0) | Voicing (0) | Voicing (0) | | B_05 | Voicing (0) | Voicing (0) | Voicing (0) |
| B_06 | Pitch (7) | Pitch (7) | Pitch (7) | | B_06 | Pitch (7) | Pitch (7) | Pitch (7) |
skipping to change at page 14, line 34 skipping to change at page 16, line 25
| B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) | | B_50 | GAIN1 (4) | GAIN1 (4) | GAIN1 (4) |
| B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) | | B_51 | GAIN1 (3) | GAIN1 (3) | GAIN1 (3) |
| B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) | | B_52 | GAIN1 (2) | GAIN1 (2) | GAIN1 (2) |
| B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) | | B_53 | GAIN1 (1) | GAIN1 (1) | GAIN1 (1) |
| B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) | | B_54 | GAIN1 (0) | GAIN1 (0) | GAIN1 (0) |
+--------+-------------+-------------+-------------+ +--------+-------------+-------------+-------------+
Notes: Notes:
xxxx (0) = LSB xxxx (0) = LSB
xxxx (nbits-1) = MSB xxxx (nbits-1) = MSB
LSF1,p = MSVQ indice of the pth stage of the two first frames LSF1,p = MSVQ* index of the pth stage of the two first frames
LSF2,p = MSVQ indice of the pth stage of the two last frames LSF2,p = MSVQ index of the pth stage of the two last frames
GAIN1 = VQ/MSVQ indice of the 1st stage GAIN1 = VQ/MSVQ index of the 1st stage
GAIN2 = MSVQ indice of the 2nd stage GAIN2 = MSVQ index of the 2nd stage
* MSVQ: Multi-Stage Vector Quantizer
Table 3.3b - The bitstream definition for MELPe 600 bps (part 2 of Table 4: Bitstream Definition for MELPe 600 bps (Part 2 of 2)
2).
The 600 bps MELPe RTP payload is constructed as per Figure 4. Note The 600 bps MELPe RTP payload is constructed as per Figure 4. Note
that bit B_01 is placed in the LSB of the first byte with all other that bit B_01 is placed in the LSB of the first byte with all other
bits in sequence. When filling octets, the least significant bits of bits in sequence. When filling octets, the least significant bits of
the seventh octet are filled with bits B_49 to B_54 respectively. the seventh octet are filled with bits B_49 to B_54, respectively.
MSB LSB MSB LSB
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 | | B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 | | B_16 | B_15 | B_14 | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 | | B_24 | B_23 | B_22 | B_21 | B_20 | B_19 | B_18 | B_17 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 | | B_32 | B_31 | B_30 | B_29 | B_28 | B_27 | B_26 | B_25 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 | | B_40 | B_39 | B_38 | B_37 | B_36 | B_35 | B_34 | B_33 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 | | B_48 | B_47 | B_46 | B_45 | B_44 | B_43 | B_42 | B_41 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 | | RSVA | RSVB | B_54 | B_53 | B_52 | B_51 | B_50 | B_49 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
Figure 4 - Packed MELPe 600 bps payload octets. Figure 4: Packed MELPe 600 bps Payload Octets
3.2 MELPe Comfort Noise Bitstream Definition 3.2. MELPe Comfort Noise Bitstream Definition
Table B.3-1 of [SCIP210] identifies the usage of MELPe 2400 bps Table B.3-1 of [SCIP210] identifies the usage of MELPe 2400 bps
parameters for conveying comfort noise. parameters for conveying comfort noise.
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| MELPe Parameter | Value | | MELPe Parameter | Value |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| msvq[0] (line spectral frequencies) | * See Note | | msvq[0] (line spectral frequencies) | * See Note |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| msvq[1] (line spectral frequencies) | Set to 0 | | msvq[1] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| msvq[2] (line spectral frequencies) | Set to 0 | | msvq[2] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| msvq[3] (line spectral frequencies) | Set to 0 | | msvq[3] (line spectral frequencies) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| fsvq (Fourier magnitudes) | Set to 0 | | fsvq (Fourier magnitudes) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| gain[0] (gain) | Set to 0 | | gain[0] (gain) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| gain[1] (gain) | * See Note | | gain[1] (gain) | * See Note |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| pitch (pitch - overall voicing) | Set to 0 | | pitch (pitch - overall voicing) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| bp (bandpass voicing) | Set to 0 | | bp (bandpass voicing) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| af (aperiodic flag/jitter index) | Set to 0 | | af (aperiodic flag/jitter index) | Set to 0 |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
| sync (sync bit) | Alternations | | sync (sync bit) | Alternations |
+-------------------------------------+----------------+ +-------------------------------------+----------------+
Note: The default values are the respective parameters from Note:
the vocoder frame. It is preferred that msvq[0] and gain[1] The default values are the respective parameters from the
values be derived by averaging the respective parameter from vocoder frame. It is preferred that msvq[0] and gain[1]
some number of previous vocoder frames. values be derived by averaging the respective parameter from
some number of previous vocoder frames.
Table 3.4 - MELPe Comfort Noise Parameters Table 5: MELPe Comfort Noise Parameters
Since only msvq[0] (also known as LSF1x or the first LSP) and gain[1] Since only msvq[0] (also known as LSF1x or the first LSP) and gain[1]
(also known as g2x or the second gain) are needed, the following bit (also known as g2x or the second gain) are needed, the following bit
order is used for comfort noise frames. order is used for comfort noise frames:
+--------+-------------+ +--------+-------------+
| Bit | Comfort | | Bit | Comfort |
| | Noise | | | Noise |
+--------+-------------+ +--------+-------------+
| B_01 | LSF10 | | B_01 | LSF10 |
| B_02 | LSF11 | | B_02 | LSF11 |
| B_03 | LSF12 | | B_03 | LSF12 |
| B_04 | LSF13 | | B_04 | LSF13 |
| B_05 | LSF14 | | B_05 | LSF14 |
| B_06 | LSF15 | | B_06 | LSF15 |
| B_07 | LSF16 | | B_07 | LSF16 |
| B_08 | g20 | | B_08 | g20 |
+--------+-------------+ +--------+-------------+
| B_09 | g21 | | B_09 | g21 |
| B_10 | g22 | | B_10 | g22 |
| B_11 | g23 | | B_11 | g23 |
| B_12 | g24 | | B_12 | g24 |
| B_13 | SYNC | | B_13 | SYNC |
+--------+-------------+ +--------+-------------+
NOTES: Notes:
g = Gain g = Gain
LSF = Line Spectral Frequencies LSF = Line Spectral Frequencies
Table 3.5 - The bitstream definition for MELPe Comfort Noise. Table 6: Bitstream Definition for MELPe Comfort Noise
The Comfort Noise MELPe RTP payload is constructed as per Figure 5. The comfort noise MELPe RTP payload is constructed as per Figure 5.
Note that bit B_01 is placed in the LSB of the first byte with all Note that bit B_01 is placed in the LSB of the first byte with all
other bits in sequence. When When filling octets, the least other bits in sequence. When filling octets, the least significant
significant bits of the second octet are filled with bits B_09 to bits of the second octet are filled with bits B_09 to B_13,
B_13 respectively. respectively.
MSB LSB MSB LSB
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 | | B_08 | B_07 | B_06 | B_05 | B_04 | B_03 | B_02 | B_01 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| RSVA | RSVB | RSVC | B_13 | B_12 | B_11 | B_10 | B_09 | | RSVA | RSVB | RSVC | B_13 | B_12 | B_11 | B_10 | B_09 |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
Figure 5 - Packed MELPe Comfort Noise payload octets. Figure 5: Packed MELPe Comfort Noise Payload Octets
3.3 Multiple MELPe frames in a RTP packet 3.3. Multiple MELPe Frames in an RTP Packet
A MELPe RTP packet MAY consist of zero or more MELPe coder frames, A MELPe RTP packet MAY consist of zero or more MELPe coder frames
followed by zero or one MELPe Comfort Noise frames. The presence of followed by zero or one MELPe comfort noise frame. The presence of a
a comfort noise frame can be deduced from the length of the RTP comfort noise frame can be deduced from the length of the RTP
payload. The default packetization interval is one coder frame payload. The default packetization interval is one coder frame
(22.5, 67.5 or 90 ms) according to the coder bit rate (2400, 1200 or (22.5, 67.5, or 90 ms) according to the coder bitrate (2400, 1200, or
600 bps). For some applications, a longer packetization interval is 600 bps). For some applications, a longer packetization interval is
used to reduce the packet rate. used to reduce the packet rate.
A MELPe RTP packet comprised of no coder frame and no comfort noise A MELPe RTP packet comprised of no coder frame and no comfort noise
frame MAY be used periodically by an end point to indicate frame MAY be used periodically by an endpoint to indicate
connectivity by an otherwise idle receiver. connectivity by an otherwise idle receiver.
All MELPe frames in a single RTP packet MUST be of the same coder bit All MELPe frames in a single RTP packet MUST be of the same coder
rate. Dynamic switching between frame rates within an RTP stream may bitrate. Dynamic switching between frame rates within an RTP stream
be permitted (if supported by both ends) provided that reserved bits, may be permitted (if supported by both ends) provided that reserved
RSVA, RSVB, and RSVC are filled in as per Table 3.6. If bit-rate bits RSVA, RSVB, and RSVC are filled in as per Table 7. If bitrate
switching is not used, all reserved bits are encoded as 0 by the switching is not used, all reserved bits are encoded as 0 by the
sender and ignored by the receiver. (RSV0 is always coded as 0). sender and ignored by the receiver. (RSV0 is always coded as 0.)
+-------------------+------+------+------+ +-------------------+------+------+------+
| Coder Bit Rate | RSVA | RSVB | RSVC | | Coder Bitrate | RSVA | RSVB | RSVC |
+-------------------+------+------+------+ +-------------------+------+------+------+
| 2400 bps | 0 | 0 | N/A | | 2400 bps | 0 | 0 | N/A |
+-------------------+------+------+------+ +-------------------+------+------+------+
| 1200 bps | 1 | 0 | 0 | | 1200 bps | 1 | 0 | 0 |
+-------------------+------+------+------+ +-------------------+------+------+------+
| 600 bps | 0 | 1 | N/A | | 600 bps | 0 | 1 | N/A |
+-------------------+------+------+------+ +-------------------+------+------+------+
| Comfort Noise | 1 | 0 | 1 | | Comfort Noise | 1 | 0 | 1 |
+-------------------+------+------+------+ +-------------------+------+------+------+
| (reserved) | 1 | 1 | N/A | | (reserved) | 1 | 1 | N/A |
+-------------------+------+------+------+ +-------------------+------+------+------+
Table 3.6 - MELPe Frame Bit Rate Indicators. Table 7: MELPe Frame Bitrate Indicators
It is important to observe that senders have the following additional It is important to observe that senders have the following additional
restrictions: restrictions:
Senders SHOULD NOT include more MELPe frames in a single RTP packet Senders SHOULD NOT include more MELPe frames in a single RTP packet
than will fit in the MTU of the RTP transport protocol. than will fit in the MTU of the RTP transport protocol.
Frames MUST NOT be split between RTP packets. Frames MUST NOT be split between RTP packets.
It is RECOMMENDED that the number of frames contained within an RTP It is RECOMMENDED that the number of frames contained within an RTP
packet is consistent with the application. For example, in a packet be consistent with the application. For example, in telephony
telephony and other real time applications where delay is important, and other real-time applications where delay is important, then the
then the fewer frames per packet the lower the delay, whereas for fewer frames per packet the lower the delay, whereas for bandwidth-
bandwidth constrained links or delay insensitive streaming messaging constrained links or delay-insensitive streaming messaging
application, more than one or many frames per packet would be applications, more than one frame per packet or many frames per
acceptable. packet would be acceptable.
Information describing the number of frames contained in an RTP Information describing the number of frames contained in an RTP
packet is not transmitted as part of the RTP payload. The way to packet is not transmitted as part of the RTP payload. The way to
determine the number of MELPe frames is to count the total number of determine the number of MELPe frames is to count the total number of
octets within the RTP packet, and divide the octet count by the octets within the RTP packet and divide the octet count by the number
number of expected octets per frame (7/11/7 per frame). Keep in mind of expected octets per frame (7/11/7 per frame). Keep in mind that
the last frame can be a 2 octet comfort noise frame. the last frame can be a 2-octet comfort noise frame.
When dynamic bit-rate switching is used and more than one frame is When dynamic bitrate switching is used and more than one frame is
contained in a RTP packet, it is RECOMMENDED to inspect the coder contained in an RTP packet, it is RECOMMENDED that the coder rate
rate bits contained in the last octet. If the coder bit rate bits contained in the last octet be inspected. If the coder bitrate
indicates a Comfort Noise frame, then inspect the third last octet indicates a comfort noise frame, then inspect the third last octet
for the coder bit rate. All MELPe speech frames in the RTP packet for the coder bitrate. All MELPe speech frames in the RTP packet
will be of this same coder bit rate. will be of this same coder bitrate.
3.4 Congestion Control Considerations 3.4. Congestion Control Considerations
The target bitrate of MELPe can be adjusted at any point in time, The target bitrate of MELPe can be adjusted at any point in time,
thus allowing congestion management. Furthermore, the amount of thus allowing congestion management. Furthermore, the amount of
encoded speech or audio data encoded in a single packet can be used encoded speech or audio data encoded in a single packet can be used
for congestion control, since packet rate is inversely proportional for congestion control, since the packet rate is inversely
to the packet duration. A lower packet transmission rate reduces the proportional to the packet duration. A lower packet transmission
amount of header overhead, but at the same time increases latency and rate reduces the amount of header overhead but at the same time
loss sensitivity, so it ought to be used with care. increases latency and loss sensitivity, so it ought to be used
with care.
Since UDP does not provide congestion control, applications that use Since UDP does not provide congestion control, applications that use
RTP over UDP SHOULD implement their own congestion control above the RTP over UDP SHOULD implement their own congestion control above the
UDP layer [RFC8085] and MAY as well implement a transport circuit UDP layer [RFC8085] and MAY also implement a transport circuit
breaker [RFC8083] (formerly [draft-ietf-avtcore-rtp-circuit- breaker [RFC8083]. Work in the RMCAT working group [RMCAT] describes
breakers]). Work in the RMCAT working group [rmcat] describes the the interactions and conceptual interfaces necessary between the
interactions and conceptual interfaces necessary between the
application components that relate to congestion control, including application components that relate to congestion control, including
the RTP layer, the higher-level media codec control layer, and the the RTP layer, the higher-level media codec control layer, and the
lower-level transport interface, as well as components dedicated to lower-level transport interface, as well as components dedicated to
congestion control functions. congestion control functions.
4 Payload Format Parameters 4. Payload Format Parameters
This RTP payload format is identified using the MELP, MELP2400, This RTP payload format is identified using the MELP, MELP2400,
MELP1200, and MELP600 media types which is registered in accordance MELP1200, and MELP600 media subtypes, which are registered in
with RFC 4855 [RFC4855] and using the template of RFC 6838 [RFC6838]. accordance with RFC 4855 [RFC4855] and per the media type
registration template from RFC 6838 [RFC6838].
4.1 Media Type Definition
Type names:
audio
Subtype name: 4.1. Media Type Definitions
MELP, MELP2400, MELP1200, and MELP600 Type name: audio
Required parameters: Subtype names: MELP, MELP2400, MELP1200, and MELP600
N/A Required parameters: N/A
Optional parameters: Optional parameters:
ptime: the recommended length of time (in milliseconds) ptime: the recommended length of time (in milliseconds)
represented by the media in a packet. It SHALL use the nearest represented by the media in a packet. It SHALL use the nearest
rounded-up ms integer packet duration. For MELPe, this rounded-up ms integer packet duration. For MELPe, this
corresponds to the values: 23, 45, 68, 90, 112, 135, 156, and corresponds to the following values: 23, 45, 68, 90, 112, 135,
180. Larger values can be used as long as they are properly 156, and 180. Larger values can be used as long as they are
rounded. See Section 6 of RFC 4566 [RFC4566]. properly rounded. See Section 6 of RFC 4566 [RFC4566].
maxptime: the maximum length of time (in milliseconds) that can maxptime: the maximum length of time (in milliseconds) that can be
be encapsulated in a packet. It SHALL use the nearest rounded- encapsulated in a packet. It SHALL use the nearest rounded-up
up ms integer packet duration. For MELPe, this corresponds to ms integer packet duration. For MELPe, this corresponds to the
the values: 23, 45, 68, 90, 112, 135, 156, and 180. Larger following values: 23, 45, 68, 90, 112, 135, 156, and 180.
values can be used as long as they are properly rounded. See Larger values can be used as long as they are properly rounded.
Section 6 of RFC 4566 [RFC4566]. See Section 6 of RFC 4566 [RFC4566].
bitrate: specifies the MELPe coder bit rates supported. bitrate: specifies the MELPe coder bitrates supported. Possible
Possible values are a comma-separated list of rates from the values are a comma-separated list of rates from the following
set: 2400, 1200, 600. The modes are listed in order of set: 2400, 1200, 600. The modes are listed in order of
preference; first is preferred. If "bitrate" is not present, preference; first is preferred. If "bitrate" is not present,
the fixed coder bit rate of 2400 MUST be used. The alternate the fixed coder bitrate of 2400 MUST be used. The alternate
encoding names, "MELP2400", "MELP1200", and "MELP600" directly encoding names "MELP2400", "MELP1200", and "MELP600" directly
specify the MELPe coder bit rate of 2400, 1200, and 600 specify the MELPe coder bitrates of 2400, 1200, and 600,
respectively and MUST NOT specify a "bitrate" parameter. respectively, and MUST NOT specify a "bitrate" parameter.
Encoding considerations:
This media type is framed and binary, see section 4.8 in RFC6838
[RFC6838].
Security considerations:
Please see the security considerations in section 8 of RFCxxxx
(this RFC).
Interoperability considerations:
Early implementations used MELP2400, MELP1200, and MELP600 to
indicate both coder type and bit rate. These media type names
should be preserved with this registration.
Published specification:
N/A
Applications that use this media type:
N/A
Additional information: Encoding considerations: These media subtypes are framed and binary;
see Section 4.8 of RFC 6838 [RFC6838].
N/A Security considerations: Please see Section 8 of RFC 8130.
Deprecated alias names for this type: Interoperability considerations: Early implementations used MELP2400,
MELP1200, and MELP600 to indicate both coder type and bitrate.
These media type names should be preserved with this registration.
N/A Published specification: N/A
Magic number(s): Applications that use this media type: N/A
N/A Additional information: N/A
File extension(s): Deprecated alias names for this type: N/A
N/A Magic number(s): N/A
Macintosh file type code(s): File extension(s): N/A
N/A Macintosh file type code(s): N/A
Person & email address to contact for further information: Person & email address to contact for further information:
Victor Demjanenko, Ph.D. Victor Demjanenko, Ph.D.
VOCAL Technologies, Ltd. VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202 520 Lee Entrance, Suite 202
Buffalo, NY 14228 Buffalo, NY 14228
USA United States of America
Phone: +1 716 688 4675 Phone: +1 716 688 4675
Email: victor.demjanenko@vocal.com Email: victor.demjanenko@vocal.com
Intended usage: Intended usage: COMMON
COMMON
Restrictions on usage:
This media type depends on RTP framing, and hence is only defined
for transfer via RTP [RFC3550]. Transport within other framing
protocols is not defined at this time.
Author:
Victor Demjanenko
Change controller: Restrictions on usage: These media subtypes depend on RTP framing and
hence are only defined for transfer via RTP [RFC3550]. Transport
within other framing protocols is not defined at this time.
IETF Payload working group delegated from the IESG. Author: Victor Demjanenko
Provisional registration? (standards tree only): Change controller: IETF Payload working group delegated from the
IESG.
No Provisional registration? (standards tree only): No
4.2 Mapping to SDP 4.2. Mapping to SDP
The mapping of the above defined payload format media type and its The mapping of the above-defined payload format media subtypes and
parameters SHALL be done according to Section 3 of RFC 4855 their parameters SHALL be done according to Section 3 of RFC 4855
[RFC4855]. [RFC4855].
The information carried in the media type specification has a The information carried in the media type specification has a
specific mapping to fields in the Session Description Protocol (SDP) specific mapping to fields in the Session Description Protocol (SDP)
[RFC4566], which is commonly used to describe RTP sessions. When SDP [RFC4566], which is commonly used to describe RTP sessions. When SDP
is used to specify sessions employing the MELPe codec, the mapping is is used to specify sessions employing the MELPe codec, the mapping is
as follows: as follows:
o The media type ("audio") goes in SDP "m=" as the media name. o The media type ("audio") goes in SDP "m=" as the media name.
o The media subtype (payload format name) goes in SDP "a=rtpmap"
as the encoding name.
o The parameter "bitrate" goes in the SDP "a=fmtp" attribute by
copying it as a "bitrate=<value>" string.
o The parameters "ptime" and "maxptime" go in the SDP "a=ptime"
and "a=maxptime" attributes, respectively.
When conveying information by SDP, the encoding name SHALL be "MELP" o The media subtype (payload format name) goes in SDP "a=rtpmap" as
(the same as the media subtype). Alternative encoding name types, the encoding name.
"MELP2400", "MELP1200", and "MELP600", MAY be used in SDP to convey
fixed bit-rate configurations. These names have been observed in o The parameter "bitrate" goes in the SDP "a=fmtp" attribute by
systems that do not support dynamic frame rate switching as specified copying it as a "bitrate=<value>" string.
by the parameter, "bitrate".
o The parameters "ptime" and "maxptime" go in the SDP "a=ptime" and
"a=maxptime" attributes, respectively.
When conveying information via SDP, the encoding name SHALL be "MELP"
(the same as the media subtype). Alternate encoding name subtypes
"MELP2400", "MELP1200", and "MELP600" MAY be used in SDP to convey
fixed-bitrate configurations. These names have been observed in
systems that do not support dynamic frame-rate switching as specified
by the parameter "bitrate".
An example of the media representation in SDP for describing MELPe An example of the media representation in SDP for describing MELPe
might be: might be:
m=audio 49120 RTP/AVP 97 m=audio 49120 RTP/AVP 97
a=rtpmap:97 MELP/8000 a=rtpmap:97 MELP/8000
An alternative example of SDP for fixed bit-rate configurations might An alternative example of SDP for fixed-bitrate configurations
be: might be:
m=audio 49120 RTP/AVP 97 100 101 102 m=audio 49120 RTP/AVP 97 100 101 102
a=rtpmap:97 MELP/8000 a=rtpmap:97 MELP/8000
a=rtpmap:100 MELP2400/8000 a=rtpmap:100 MELP2400/8000
a=rtpmap:101 MELP1200/8000 a=rtpmap:101 MELP1200/8000
a=rtpmap:102 MELP600/8000 a=rtpmap:102 MELP600/8000
If the encoding name "MELP" is received without a "bitrate" If the encoding name "MELP" is received without a "bitrate"
parameter, the fixed coder bit rate of 2400 MUST be used. The parameter, the fixed coder bitrate of 2400 MUST be used. The
alternate encoding names, "MELP2400", "MELP1200", and "MELP600" alternate encoding names "MELP2400", "MELP1200", and "MELP600"
directly specify the MELPe coder bit rate of 2400, 1200, and 600 directly specify the MELPe coder bitrates of 2400, 1200, and 600,
respectively and MUST NOT specify a "bitrate" parameter. respectively, and MUST NOT specify a "bitrate" parameter.
The optional media type parameter, "bitrate", when present, MUST be The optional media type parameter "bitrate", when present, MUST be
included in the "a=fmtp" attribute in the SDP, expressed as a media included in the "a=fmtp" attribute in the SDP, expressed as a media
type string in the form of a semicolon-separated list of type string in the form of a semicolon-separated list of
parameter=value pairs. The string, "value", can be one or more of parameter=value pairs. The string "value" can be one or more of
2400, 1200, and 600 separated by commas (where each bit-rate value 2400, 1200, and 600, separated by commas (where each bitrate value
indicates the corresponding MELPe coder). An example of the media indicates the corresponding MELPe coder). An example of the media
representation in SDP for describing MELPe when all three coder bit representation in SDP for describing MELPe when all three coder
rates are supported might be: bitrates are supported might be:
m=audio 49120 RTP/AVP 97 m=audio 49120 RTP/AVP 97
a=rtpmap:97 MELP/8000 a=rtpmap:97 MELP/8000
a=fmtp:97 bitrate=2400,600,1200 a=fmtp:97 bitrate=2400,600,1200
Parameter ptime can not be used for the purpose of specifying MELPe Parameter "ptime" cannot be used for the purpose of specifying the
operating mode, due to fact that for the certain values it will be MELPe operating mode, due to the fact that for certain values it will
impossible to distinguish which mode is about to be used (e.g. when be impossible to distinguish which mode is about to be used (e.g.,
ptime=68, it would be impossible to distinguish if packet is carrying when ptime=68, it would be impossible to distinguish if the packet is
1 frames of 67.5 ms or 3 frames of 22.5 ms etc.). carrying one frame of 67.5 ms or three frames of 22.5 ms).
Note that the payload format (encoding) names are commonly shown in Note that the payload format (encoding) names are commonly shown in
upper case. Media subtypes are commonly shown in lower case. These upper case. Media subtypes are commonly shown in lower case. These
names are case-insensitive in both places. Similarly, parameter names are case insensitive in both places. Similarly, parameter
names are case-insensitive both in media subtype name and in the names are case insensitive in both the media subtype name and the
default mapping to the SDP a=fmtp attribute default mapping to the SDP a=fmtp attribute.
4.3 Declarative SDP Considerations 4.3. Declarative SDP Considerations
For declarative media, the "bitrate" parameter specifes the possible For declarative media, the "bitrate" parameter specifies the possible
bit rates used by the sender. Multiple MELPe rtpmap values (such as bitrates used by the sender. Multiple MELPe rtpmap values (such as
97, 98, and 99 as used below) MAY be used to convey MELPe coded voice 97, 98, and 99, as used below) MAY be used to convey MELPe-coded
at different bit rates. The receiver can then select an appropriate voice at different bitrates. The receiver can then select an
MELPe codec by using 97, 98, or 99. appropriate MELPe codec by using 97, 98, or 99.
m=audio 49120 RTP/AVP 97 98 99 m=audio 49120 RTP/AVP 97 98 99
a=rtpmap:97 MELP/8000 a=rtpmap:97 MELP/8000
a=fmtp:97 bitrate=2400 a=fmtp:97 bitrate=2400
a=rtpmap:98 MELP/8000 a=rtpmap:98 MELP/8000
a=fmtp:98 bitrate=1200 a=fmtp:98 bitrate=1200
a=rtpmap:99 MELP/8000 a=rtpmap:99 MELP/8000
a=fmtp:99 bitrate=600 a=fmtp:99 bitrate=600
4.4 Offer/Answer SDP Considerations 4.4. Offer/Answer SDP Considerations
In an Offer/Answer mode [RFC3264], "bitrate" is a bi-directional In the Offer/Answer model [RFC3264], "bitrate" is a bidirectional
parameter. Both sides MUST use a common "bitrate" value or values. parameter. Both sides MUST use a common "bitrate" value or values.
The offer contains the bit rates supported by the offerer listed in The offer contains the bitrates supported by the offerer, listed in
its preferred order. The answerer MAY agree to any bit rate by its preferred order. The answerer MAY agree to any bitrate by
listing the bit rate first in the answerer response. Additionally listing the bitrate first in the answerer response. Additionally,
the answerer MAY indicate any secondary bit rate or bit rates that it the answerer MAY indicate any secondary bitrate or bitrates that it
supports. The initial bit rate used by both parties SHALL be the supports. The initial bitrate used by both parties SHALL be the
first bit rate specified in the answerer response. first bitrate specified in the answerer response.
For example if offerer bit rates are "2400,600", and answer bit rates For example, if offerer bitrates are "2400,600" and answer bitrates
are "600,2400", the initial bit rate is 600. If other bit rates are are "600,2400", the initial bitrate is 600. If other bitrates are
provided by the answerer, any common bit rate between offer and provided by the answerer, any common bitrate between the offer and
answer MAY be used at any time in the future. Activation of these answer MAY be used at any time in the future. Activation of these
other common bit rates is beyond the scope of this document. other common bitrates is beyond the scope of this document.
The use of a lower bit rate is often important for a case such as The use of a lower bitrate is often important for a case such as when
when one end point utilizes a bandwidth constrained link (e.g. 1200 one endpoint utilizes a bandwidth-constrained link (e.g., 1200 bps
bps radio link or slower), where only the lower coder bit rate will radio link or slower), where only the lower coder bitrate will work.
work.
5 Discontinious Transmission 5. Discontinuous Transmissions
A primary application of MELPe is for radio communications of voice A primary application of MELPe is for radio communications of voice
conversations and discontinuous transmissions are normal. When MELPe conversations, and discontinuous transmissions are normal. When
is used in an IP network, MELPe RTP packet transmissions may cease MELPe is used in an IP network, MELPe RTP packet transmissions may
and resume frequently. RTP SSRC sequence number gaps indicate lost cease and resume frequently. RTP synchronization source (SSRC)
packets to be filled by PLC while abrupt loss of RTP packets indicate sequence number gaps indicate lost packets to be filled by PLC, while
intended discontinuous transmission. abrupt loss of RTP packets indicates intended discontinuous
transmissions.
If a MELPe coder so desires, it may send a comfort noise frame as per If a MELPe coder so desires, it may send a comfort noise frame as per
SCIP-210 Appendix B [SCIP210] prior to ceasing transmission. A Appendix B of [SCIP210] prior to ceasing transmission. A receiver
receiver may optionally use comfort noise during its silence periods. may optionally use comfort noise during its silence periods. No SDP
No SDP negotiations are required. negotiations are required.
6 Packet Loss Concealment 6. Packet Loss Concealment
MELPe packet loss concealment (PLC) uses the special properties and MELPe packet loss concealment (PLC) uses the special properties and
coding for the pitch/voicing parameter of the MELPe 2400 bps coder. coding for the pitch/voicing parameter of the MELPe 2400 bps coder.
The PLC erasure indication utilizes any of the errored encodings of a The PLC erasure indication utilizes any of the errored encodings of a
non-voiced frame as identified in Table 1 of [MELPE]. For the sake non-voiced frame as identified in Table 1 of [MELPE]. For the sake
of simplicity it is preferred to use a code value of 3 for the of simplicity, it is preferred that a code value of 3 for the
pitch/voicing parameter (represented by the bits P6 to P0 in Table pitch/voicing parameter (represented by the bits P6 to P0 in Table 1
3.1). Hence, set bits P0 and P1 to one and bits P2, P3, P4, P5, and of this document) be used. Hence, set bits P0 and P1 to one and bits
P6 to zero. P2, P3, P4, P5, and P6 to zero.
When using PLC in a 1200 bps or 600 bps mode, the MELPe 2400 bps When using PLC in 1200 bps or 600 bps mode, the MELPe 2400 bps
decoder is called three or four times respectively to cover the loss decoder is called three or four times, respectively, to cover the
of a MELPe frame. loss of a MELPe frame.
7 IANA Considerations 7. IANA Considerations
This memo requests that IANA registers MELP, MELP2400, MELP1200, and IANA has registered MELP, MELP2400, MELP1200, and MELP600 as
MELP600 as specified in Section 4.1. The media type is also specified in Section 4.1. IANA has also added these media subtypes
requested to be added to the IANA registry for "RTP Payload Format to the "RTP Payload Format media types" registry
MIME types" (http://www.iana.org/assignments/rtp-parameters). (http://www.iana.org/assignments/rtp-parameters).
8 Security Considerations 8. Security Considerations
RTP packets using the payload format defined in this specification RTP packets using the payload format defined in this specification
are subject to the security considerations discussed in the RTP are subject to the security considerations discussed in the RTP
specification [RFC3550], and in any applicable RTP profile such as specification [RFC3550] and in any applicable RTP profile such as
RTP/AVP [RFC3551], RTP/AVPF [RFC4855], RTP/SAVP [RFC3711] or RTP/AVP [RFC3551], RTP/AVPF [RFC4585], RTP/SAVP [RFC3711], or
RTP/SAVPF [RFC5124]. However, as "Securing the RTP Protocol RTP/SAVPF [RFC5124]. However, as discussed in [RFC7202], it is not
Framework: Why RTP Does Not Mandate a Single Media Security Solution" an RTP payload format's responsibility to discuss or mandate what
[RFC7202] discusses, it is not an RTP payload format's responsibility solutions are used to meet such basic security goals as
to discuss or mandate what solutions are used to meet the basic confidentiality, integrity, and source authenticity for RTP in
security goals like confidentiality, integrity and source general. This responsibility lies with anyone using RTP in an
authenticity for RTP in general. This responsibility lays on anyone application. They can find guidance on available security mechanisms
using RTP in an application. They can find guidance on available and important considerations in [RFC7201]. Applications SHOULD use
security mechanisms and important considerations in Options for one or more appropriate strong security mechanisms. The rest of this
Securing RTP Sessions [RFC7201]. Applications SHOULD use one or more section discusses the security-impacting properties of the payload
appropriate strong security mechanisms. The rest of this security format itself.
consideration section discusses the security impacting properties of
the payload format itself.
This RTP payload format and the MELPe decoder do not exhibit any This RTP payload format and the MELPe decoder do not exhibit any
significant non-uniformity in the receiver-side computational significant non-uniformity in the receiver-side computational
complexity for packet processing, and thus are unlikely to pose a complexity for packet processing and thus are unlikely to pose a
denial-of-service threat due to the receipt of pathological data. denial-of-service threat due to the receipt of pathological data.
Nor does the RTP payload format contain any active content. Additionally, the RTP payload format does not contain any active
content.
With respect to VAD and its effect on bit rate, please see security
consideration in RFC6562 [RFC6562].
9 RFC Editor Considerations Please see the security considerations discussed in [RFC6562]
regarding VAD and its effect on bitrates.
Note to RFC Editor: This section may be removed after carrying out 9. References
all the instructions of this section.
10 References 9.1. Normative References
10.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[draft-ietf-avtcore-rtp-circuit-breakers] Perkins, C. and V. Singh, [RFC2736] Handley, M. and C. Perkins, "Guidelines for Writers of RTP
"Multimedia Congestion Control: Circuit Breakers for Unicast RTP Payload Format Specifications", BCP 36, RFC 2736,
Sessions", draft-ietf-avtcore-rtp-circuit-breakers-18 (work in DOI 10.17487/RFC2736, December 1999,
progress), August 18, 2016. <http://www.rfc-editor.org/info/rfc2736>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
requirement Levels", BCP 14, RFC 2119, March 1997. with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>.
[RFC2736] Handley, M. and Perkins, C., "Guidelines for Writers of RTP [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Payload Format Specifications", BCP 36, RFC 2736, December 1999. Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3264] Rosenberg, J. and Schulzrinne, H., "An Offer/Answer Model [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
with the Session Description Protocol (SDP)" IETF RFC 3264, June Video Conferences with Minimal Control", STD 65, RFC 3551,
2002. DOI 10.17487/RFC3551, July 2003,
<http://www.rfc-editor.org/info/rfc3551>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and Jacobson, [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
V., "RTP: A Transport Protocol for Real-Time Applications", IETF RFC Norrman, "The Secure Real-time Transport Protocol (SRTP)",
3550, July 2003. RFC 3711, DOI 10.17487/RFC3711, March 2004,
<http://www.rfc-editor.org/info/rfc3711>.
[RFC3551] Schulzrinne, H., and Casner, S., "RTP Profile for Audio and [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Video Conferences with Minimal Control" IETF RFC 3551, July 2003. Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC3711] Baugher, et al., "The Secure Real Time Transport Protocol", [RFC4855] Casner, S., "Media Type Registration of RTP Payload
IETF RFC 3711, March 2004. Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<http://www.rfc-editor.org/info/rfc4855>.
[RFC4566] Handley, M., Jacobson, V. and Perkins, C., "SDP: Session [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Description Protocol", IETF RFC RFC4566, July 2006. Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124,
February 2008, <http://www.rfc-editor.org/info/rfc5124>.
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC6562] Perkins, C. and JM. Valin, "Guidelines for the Use of
Formats", RFC 4855, February 2007. Variable Bit Rate Audio with Secure RTP", RFC 6562,
DOI 10.17487/RFC6562, March 2012,
<http://www.rfc-editor.org/info/rfc6562>.
[RFC5124] Ott, J. and Carrara, E., "Extended Secure RTP Profile for [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Real-time Transport Control Protocol (RTCP)-Based Specifications and Registration Procedures", BCP 13,
Feedback(RTP/SAVPF)", RFC 5124, February 2008. RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[RFC6562] Perkins, C. and Valin, J. M., "Guidelines for the Use of [RFC8083] Perkins, C. and V. Singh, "Multimedia Congestion Control:
Variable Bit Rate Audio with Secure RTP", RFC 6562, March 2012. Circuit Breakers for Unicast RTP Sessions", RFC 8083,
DOI 10.17487/RFC8083, March 2017,
<http://www.rfc-editor.org/info/rfc8083>.
[RFC6838] Freed, N., Klensin, J. and Hansen, T., "Media Type [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Specifications and Registration Procedures", BCP 13, RFC 6838, Guidelines", RFC 8085, DOI 10.17487/RFC8085, March 2017,
January 2013. <http://www.rfc-editor.org/info/rfc8085>.
[RFC8083] Perkins, C. and V. Singh, "Multimedia Congestion Control: [MELP] Department of Defense Telecommunications Standard,
Circuit Breakers for Unicast RTP Sessions", RFC 8083, January 2017. "Analog-to-Digital Conversion of Voice by 2,400 Bit/Second
Mixed Excitation Linear Prediction (MELP)", MIL-STD-3005,
December 1999.
[RFC8085] Eggert, L., Fairhurst, G. and Shepherd, G., "UDP Usage [MELPE] North Atlantic Treaty Organization (NATO), "The 600 Bit/S,
Guidelines", RFC 8085, February 2017. 1200 Bit/S and 2400 Bit/S NATO Interoperable Narrow Band
Voice Coder", STANAG No. 4591, January 2006.
[MELP] Department of Defense Telecommunications Standard, "Analog-to- [SCIP210] National Security Agency, "SCIP Signaling Plan", SCIP-210,
Digital Conversion of Voice by 2,400 Bit/Second Mixed Excitation December 2007.
Linear Prediction (MELP)", MIL-STD-3005, December 1999.
[MELPE] North Atlantic Treaty Organization (NATO), "The 600 Bit/S, 9.2. Informative References
1200 Bit/S and 2400 Bit/S NATO Interoperable Narrow Band Voice
Coder", STANAG No. 4591, January 2006.
[SCIP210] National Security Agency, "SCIP Signaling Plan", SCIP-210, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
December 2007. "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
DOI 10.17487/RFC4585, July 2006,
<http://www.rfc-editor.org/info/rfc4585>.
10.2 Informative References [RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP
Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,
<http://www.rfc-editor.org/info/rfc7201>.
[RFC7201] Westerlund, M. and Perkins, C., "Options for Securing RTP [RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP
Sessions", RFC 7201, April 2014. Framework: Why RTP Does Not Mandate a Single Media
Security Solution", RFC 7202, DOI 10.17487/RFC7202,
April 2014, <http://www.rfc-editor.org/info/rfc7202>.
[RFC7202] Perkins, C. and Westerlund, M., "Securing the RTP [RMCAT] IETF, RTP Media Congestion Avoidance Techniques (rmcat)
Framework: Why RTP Does Not Mandate a Single Media Security Working Group,
Solution", RFC 7202, April 2014. <https://datatracker.ietf.org/wg/rmcat/about/>.
Authors' Addresses Authors' Addresses
Victor Demjanenko, Ph.D. Victor Demjanenko, Ph.D.
VOCAL Technologies, Ltd. VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202 520 Lee Entrance, Suite 202
Buffalo, NY 14228 Buffalo, NY 14228
USA United States of America
Phone: +1 716 688 4675 Phone: +1 716 688 4675
Email: victor.demjanenko@vocal.com Email: victor.demjanenko@vocal.com
David Satterlee David Satterlee
VOCAL Technologies, Ltd. VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202 520 Lee Entrance, Suite 202
Buffalo, NY 14228 Buffalo, NY 14228
USA United States of America
Phone: +1 716 688 4675 Phone: +1 716 688 4675
Email: david.satterlee@vocal.com Email: david.satterlee@vocal.com
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