draft-ietf-avtext-splicing-for-rtp-10.txt   draft-ietf-avtext-splicing-for-rtp-11.txt 
AVTEXT Working Group J. Xia AVTEXT Working Group J. Xia
Internet-Draft Huawei Internet-Draft Huawei
Intended status: Informational October 10, 2012 Intended status: Informational October 22, 2012
Expires: April 12, 2013 Expires: April 25, 2013
Content Splicing for RTP Sessions Content Splicing for RTP Sessions
draft-ietf-avtext-splicing-for-rtp-10 draft-ietf-avtext-splicing-for-rtp-11
Abstract Abstract
Content splicing is a process that replaces the content of a main Content splicing is a process that replaces the content of a main
multimedia stream with other multimedia content, and delivers the multimedia stream with other multimedia content, and delivers the
substitutive multimedia content to the receivers for a period of substitutive multimedia content to the receivers for a period of
time. Splicing is commonly used for local advertisement insertion by time. Splicing is commonly used for local advertisement insertion by
cable operators, replacing a national advertisement content with a cable operators, replacing a national advertisement content with a
local advertisement. local advertisement.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 12, 2013. This Internet-Draft will expire on April 25, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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RTCP packets received from downstream relate to the substitutive RTCP packets received from downstream relate to the substitutive
content must be terminated on the mixer without any further content must be terminated on the mixer without any further
processing. processing.
4.3. Considerations for Handling Media Clipping at the RTP Layer 4.3. Considerations for Handling Media Clipping at the RTP Layer
This section provides informative guideline about how media clipping This section provides informative guideline about how media clipping
is shaped and how the mixer deal with the media clipping only at the is shaped and how the mixer deal with the media clipping only at the
RTP layer. Dealing with the media clipping at the RTP layer just do RTP layer. Dealing with the media clipping at the RTP layer just do
a good quality implementation, perfectly erasing the media clipping a good quality implementation, perfectly erasing the media clipping
needs more considerations in the higher layers, how to realize it is needs more considerations at the higher layers, how the media
outside of the scope of this memo. clipping is erased at the higher layers is outside of the scope of
this memo.
If the time slot for substitutive content mismatches (is shorter or If the time slot for substitutive content mismatches (is shorter or
longer than) the duration of the main content to be replaced, then longer than) the duration of the main content to be replaced, then
media clipping may occur at the splicing point and thus impact the media clipping may occur at the splicing point and thus impact the
user's experience. user's experience.
If the substitutive content has shorter duration from the main If the substitutive content has shorter duration from the main
content, then there will be a gap in the output RTP stream. The RTP content, then there will be a gap in the output RTP stream. The RTP
sequence number will be contiguous across this gap, but there will be sequence number will be contiguous across this gap, but there will be
an unexpected jump in the RTP timestamp. This gap will cause the an unexpected jump in the RTP timestamp. This gap will cause the
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invalidate the undetectability goal, but in the common case the invalidate the undetectability goal, but in the common case the
receiver will consider the splicer as the main media source. receiver will consider the splicer as the main media source.
Commonly no RTP level security mechanism is employed. Instead only Commonly no RTP level security mechanism is employed. Instead only
payload security mechanisms (e.g., ISMACryp [ISMACryp]) are used. If payload security mechanisms (e.g., ISMACryp [ISMACryp]) are used. If
any payload internal security mechanisms are used, only the RTP any payload internal security mechanisms are used, only the RTP
sender and the RTP receiver can learn the security keying material sender and the RTP receiver can learn the security keying material
generated by such internal security mechanism, in which case, any generated by such internal security mechanism, in which case, any
middlebox (e.g., splicer) between the RTP sender and the RTP receiver middlebox (e.g., splicer) between the RTP sender and the RTP receiver
can't get such keying material, and thus fail to perform splicing. can't get such keying material, and thus fail to perform splicing.
This would require a new method to be defined to make the splicer
learn the security keying material, but which is out of scope of this
memo.
7. IANA Considerations 7. IANA Considerations
No IANA actions are required. No IANA actions are required.
8. Acknowledgments 8. Acknowledgments
The following individuals have reviewed the earlier versions of this The following individuals have reviewed the earlier versions of this
specification and provided very valuable comments: Colin Perkins, specification and provided very valuable comments: Colin Perkins,
Magnus Westerlund, Roni Even, Tom Van Caenegem, Joerg Ott, David R Magnus Westerlund, Roni Even, Tom Van Caenegem, Joerg Ott, David R
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