draft-ietf-payload-tsvcis-04.txt   draft-ietf-payload-tsvcis-05.txt 
Payload Working Group Victor Demjanenko Payload Working Group Victor Demjanenko
Internet-Draft John Punaro Internet-Draft John Punaro
Intended Status: Standards Track David Satterlee Intended Status: Standards Track David Satterlee
VOCAL Technologies, Ltd. VOCAL Technologies, Ltd.
Expires: April 27, 2020 October 25, 2019 Expires: October 8, 2020 April 10, 2020
RTP Payload Format for TSVCIS Codec RTP Payload Format for TSVCIS Codec
draft-ietf-payload-tsvcis-04 draft-ietf-payload-tsvcis-05
Status of This Memo Status of This Memo
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
| H | G | F | E | D | C | B | A | | H | G | F | E | D | C | B | A |
+------+------+------+------+------+------+------+------+ +------+------+------+------+------+------+------+------+
This packing method places the three-bit field "first" in the lowest This packing method places the three-bit field "first" in the lowest
bits followed by the next five-bit field. Parameters may be split bits followed by the next five-bit field. Parameters may be split
between octets with the most significant bits in the earlier octet. between octets with the most significant bits in the earlier octet.
Any unfilled bits in the last octet MUST be filled with zero. Any unfilled bits in the last octet MUST be filled with zero.
In order to accommodate a varying amount of TSVCIS augmented speech In order to accommodate a varying amount of TSVCIS augmented speech
data, it is only necessary to specify the number of octets containing data, an octet count specifies the number of octets representing
the packed TSVCIS parameters. The encoding to do so is presented in the packed TSVCIS parameters. The encoding to do so is presented in
Section 3.2. TSVCIS specifically uses the NRL VDR in two Section 3.2. TSVCIS specifically uses the NRL VDR in two
configurations using 15 and 35 packed octet parameters [TSVCIS]. configurations using a fixed set of 15 and 35 packed octet
parameters in a standardized order [TSVCIS].
3. Payload Format 3. Payload Format
The TSVCIS codec augments the standard MELP 2400, 1200 and 600 The TSVCIS codec augments the standard MELP 2400, 1200 and 600
bitrates and hence uses 22.5, 67.5, or 90 ms frames with a sampling bitrates and hence 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 rate clock of 8 kHz, so the RTP timestamp MUST be in units of 1/8000
of a second. of a second.
The RTP payload for TSVCIS has the format shown in Figure 1. No The RTP payload for TSVCIS 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
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speech is 54, which fits in 7 octets (with two rate code bits). For speech is 54, which fits in 7 octets (with two rate code bits). For
MELPe 1200 bps speech, the total number of bits used is 81, which MELPe 1200 bps speech, the total number of bits used is 81, which
fits in 11 octets (with three rate code bits and four unused bits). fits in 11 octets (with three rate code bits and four unused bits).
For MELPe 600 bps speech, the total number of bits used is 54, which For MELPe 600 bps speech, the total number of bits used is 54, which
fits in 7 octets (with two rate code bits). The comfort noise frame fits in 7 octets (with two rate code bits). The comfort noise frame
consists of 13 bits, which fits in 2 octets (with three rate code consists of 13 bits, which fits in 2 octets (with three rate code
bits). TSVCIS packed parameters will use the last code combination bits). TSVCIS packed parameters will use the last code combination
in a trailing byte as discussed in Section 3.2. in a trailing byte as discussed in Section 3.2.
It should be noted that CODB for MELPe 600 bps mode MAY deviate from It should be noted that CODB for MELPe 600 bps mode MAY deviate from
the value in Table 1 when bit 55 is used as an end-to-end framing the value in Table 1 when bit 55 is used as an alternating 1/0
bit. Frame decoding would remain distinct as CODA being zero on its end-to-end framing bit. Frame decoding would remain distinct as CODA
own would indicate a 7-byte frame for either 2400 or 600 bps rate and being zero on its own would indicate a 7-byte frame for either 2400
the use of 600 bps speech coding could be deduced from the RTP or 600 bps rate and the use of 600 bps speech coding could be deduced
timestamp (and anticipated by the SDP negotiations). from the RTP timestamp (and anticipated by the SDP negotiations).
3.1.1. 2400 bps Bitstream Structure 3.1.1. 2400 bps Bitstream Structure
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 CODA MUST be filled with 0 and CODB SHOULD be filled with 0 as that CODA MUST be filled with 0 and CODB SHOULD be filled with 0 as
per Section 3.1. CODB MAY contain an end-to-end framing bit if per Section 3.1. CODB MAY contain an end-to-end framing bit if
required by the endpoints. required by the endpoints.
MSB LSB MSB LSB
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
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