Internet DRAFT - draft-ietf-mmusic-decoding-dependency
draft-ietf-mmusic-decoding-dependency
Network Working Group T. Schierl
Internet-Draft Fraunhofer HHI
Intended status: Standards Track S. Wenger
Expires: October 2, 2009 Nokia
April 3, 2009
Signaling media decoding dependency in Session Description Protocol
(SDP)
draft-ietf-mmusic-decoding-dependency-08
Status of this Memo
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Abstract
This memo defines semantics that allow for signaling the decoding
dependency of different media descriptions with the same media type in
the Session Description Protocol (SDP). This is required, for example,
if media data is separated and transported in different network streams
as a result of the use of a layered or multiple descriptive media coding
process.
A new grouping type "DDP" -- decoding dependency -- is defined, to be
used in conjunction with RFC 3388 entitled "Grouping of Media Lines in
the Session Description Protocol". In addition, an attribute is
specified describing the relationship of the media streams in a "DDP"
group indicated by media identification attribute(s) and media format
description(s).
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Table of Contents
1. Introduction .................................................. 4
2. Terminology ................................................... 5
3. Definitions ................................................... 5
4. Motivation, Use Cases, and Architecture ....................... 6
4.1. Motivation .................................................. 6
4.2. Use cases ................................................... 8
5. Signaling Media Dependencies .................................. 8
5.1. Design Principles ........................................... 8
5.2. Semantics ................................................... 9
5.2.1. SDP grouping semantics for decoding dependency ............ 9
5.2.2. "depend" attribute for dependency signaling per media-stream
................................................................... 9
6. Usage of new semantics in SDP ................................ 11
6.1. Usage with the SDP Offer/Answer Model ...................... 11
6.2. Declarative usage .......................................... 12
6.3. Usage with AVP and SAVP RTP profiles ....................... 12
6.4. Usage with Capability Negotiation .......................... 12
6.5. Examples ................................................... 13
7. Security Considerations ...................................... 15
8. IANA Considerations .......................................... 15
9. Informative note on RFC 3388bis .............................. 16
10. References ................................................... 16
10.1. Normative References ....................................... 16
10.2. Informative References ..................................... 17
Appendix A. Acknowledgements .................................... 18
Authors' Addresses ............................................... 18
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1. Introduction
An SDP session description may contain one or more media
descriptions, each identifying a single media stream. A media
description is identified by one "m=" line. Today, if more than one
"m=" lines exist indicating the same media type, a receiver cannot
identify a specific relationship between those media.
A Multiple Description Coding (MDC) or layered Media Bitstream
contains, by definition, one or more Media Partitions that are
conveyed in their own media stream. The cases we are interested in
are layered and MDC Bitstreams with two or more Media Partitions.
Carrying more than one Media Partition in its own session is one of
the key use cases for employing layered or MDC coded media. Senders,
network elements, or receivers can suppress
sending/forwarding/subscribing/decoding individual Media Partitions
and still preserve perhaps suboptimal, but still useful media
quality.
One property of all Media Bitstreams relevant to this memo is that
their Media Partitions have a well-defined usage relationship. For
example, in layered coding, "higher" Media Partitions are useless
without "lower" ones. In MDC coding, Media Partitions are
complementary -- the more Media Partitions one receives, the better a
reproduced quality may be. This document defines an SDP extension to
indicate such a decoding dependency.
Trigger for the present memo has been the standardization process of
the RTP payload format for the Scalable Video Coding extension to
ITU-T Rec. H.264 / MPEG-4 AVC [I-D.ietf-avt-rtp-svc]. When drafting
[I-D.ietf-avt-rtp-svc], it was observed that the aforementioned lack
in signaling support is one that is not specific to SVC, but applies
to all layered or MDC codecs. Therefore, this memo presents a
generic solution. Likely, the second technology utilizing the
mechanisms of this memo will be Multi-View video coding. In Multi
View Coding (MVC) [I-D.wang-avt-rtp-mvc] layered dependencies between
views are used to increase the coding efficiency, and, therefore, the
properties of MVC with respect to the SDP signaling are comparable to
those of SVC.
The mechanisms defined herein are media transport protocol dependent,
and applicable only in conjunction with the use of RTP [RFC3550].
The SDP grouping of Media Lines of different media types is out of
scope of this memo.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
3. Definitions
Media stream:
As per [RFC4566].
Media Bitstream:
A valid, decodable stream, containing all media partitions generated
by the encoder. A Media Bitstream normally conforms to a media
coding standard.
Media Partition:
A subset of a Media Bitstream intended for independent
transportation. An integer number of Media Partitions forms a Media
Bitstream. In layered coding, a Media Partition represents one or
more layers that are handled as a unit. In MDC coding, a Media
Partition represents one or more descriptions that are handled as a
unit.
Decoding dependency:
The class of relationships media partitions have to each other. At
present, this memo defines two decoding dependencies: layered coding
and multiple description coding.
Layered coding dependency:
Each Media Partition is only useful (i.e. can be decoded) when all of
the Media Partitions it depends on are available. The dependencies
between the Media Partitions therefore create a directed graph.
Note: normally, in layered coding, the more Media Partitions are
employed (following the rule above), the better a reproduced quality
is possible.
Multi description coding (MDC) dependency:
N of M Media Partitions are required to form a Media Bitstream, but
there is no hierarchy between these Media Partitions. Most MDC
schemes aim at an increase of reproduced media quality when more
media partitions are decoded. Some MDC schemes require more than one
Media Partition to form an Operation Point.
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Operation Point:
In layered coding, a subset of a layered Media Bitstream that
includes all Media Partitions required for reconstruction at a
certain point of quality, error resilience, or another property, and
does not include any other Media Partitions. In MDC coding, a subset
of an MDC Media Bitstream that is compliant with the MDC coding
standard in question.
4. Motivation, Use Cases, and Architecture
4.1. Motivation
This memo is concerned with two types of decoding dependencies:
layered and multi-description. The transport of layered and multi
description coding share as key motivators the desire for media
adaptation to network conditions, i.e., related to bandwidth, error
rates, connectivity of endpoints in multicast or broadcast scenarios,
and similar.
o Layered decoding dependency:
In layered coding, the partitions of a Media Bitstream are known as
media layers or simply layers. One or more layers may be
transported in different media streams in the sense of [RFC4566].
A classic use case is known as receiver-driven layered multicast,
in which a receiver selects a combination of media streams in
response to quality or bit-rate requirements.
Back in the mid 1990s, the then available layered media formats and
codecs envisioned primarily (or even exclusively) a one-dimensional
hierarchy of layers. That is, each so-called enhancement layer
referred to exactly one layer "below". The single exception has
been the base layer, which is self-contained. Therefore, the
identification of one enhancement layer fully specifies the
Operation Point of a layered coding scheme, including knowledge
about all the other layers that need to be decoded.
SDP [RFC4566] contains rudimentary support for exactly this use
case and media formats, in that it allows for signaling a range of
transport addresses in a certain media description. By definition,
a higher transport address identifies a higher layer in the one-
dimensional hierarchy. A receiver needs only to decode data
conveyed over this transport address and lower transport addresses
to decode this Operation Point.
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Newer media formats depart from this simple one-dimensional
hierarchy, in that highly complex (at least tree-shaped) dependency
hierarchies can be implemented. Compelling use cases for these
complex hierarchies have been identified by industry. Support for
it is therefore desirable. However, SDP, in its current form, does
not allow for the signaling of these complex relationships.
Therefore, receivers cannot make an informed decision on which
layers to subscribe (in case of layered multicast).
Layered decoding dependencies may also exist in a Multi View Coding
environment. Views may be coded using inter-view dependencies to
increase coding efficiency. This results in Media Bitstreams,
which logically may be separated into Media Partitions representing
different views of the reconstructed video signal. These Media
Partitions cannot be decoded independently, and, therefore, other
Media Partitions are required for reconstruction. To express this
relationship, the signaling needs to express the dependencies of
the views which in turn are Media Partitions in the sense of this
document.
o Multi descriptive decoding dependency:
In the most basic form of MDC, each Media Partition forms an
independent representation of the media. That is, decoding of any
of the Media Partitions yields useful reproduced media data. When
more than one Media Partition is available, then a decoder can
process them jointly, and the resulting media quality increases.
The highest reproduced quality is available if all original Media
Partitions are available for decoding.
More complex forms of multiple description coding can also be
envisioned, i.e. where, as a minimum, N out of M total Media
Partitions need to be available to allow meaningful decoding.
MDC has not yet been embraced heavily by the media standardization
community, though it is subject of a lot of academic research. As
an example, we refer to [MDC].
In this memo, we cover MDC because we a) envision that MDC media
formats will come into practical use within the lifetime of this
memo, and b) the solution for its signaling is very similar to the
one of layered coding.
o Other decoding dependency relationships:
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At the time of writing, no decoding dependency relationships beyond
the two mentioned above have been identified that would warrant
standardization. However, the mechanisms of this memo could be
extended by introducing new codepoints for new decoding dependency
types. If such an extension becomes necessary, as formally
required in section 5.2.2, the new decoding dependency type MUST be
documented in an IETF standard's track document.
4.2. Use cases
o Receiver driven layered multicast:
This technology is discussed in [RFC3550] and references therein.
We refrain from elaborating further; the subject is well known and
understood.
o Multiple end-to-end transmission with different properties:
Assume a unicast and point-to-point topology, wherein one endpoint
sends media to another. Assume further that different forms of
media transmission are available. The difference may lie in the
cost of the transmission (free, charged), in the available
protection (unprotected/secure), in the quality of service
(guaranteed quality / best effort), or other factors.
Layered and MDC coding allow to match the media characteristics to
the available transmission path(s). For example, in layered
coding, it makes sense to convey the base layer over high QoS.
Enhancement layers, on the other hand, can be conveyed over best
effort, as they are "optional" in their characteristic -- nice to
have, but non-essential for media consumption. In a different
scenario, the base layer may be offered in a non-encrypted session
as a free preview. An encrypted enhancement layer references this
base layer and allows optimal quality play-back; however, it is
only accessible to users who have the key, which may have been
distributed by a conditional access mechanism.
5. Signaling Media Dependencies
5.1. Design Principles
The dependency signaling is only feasible between media descriptions
described with an "m="-line and with an assigned media identification
attribute ("mid"), as defined in [RFC3388]. All media descriptions
grouped according to this specification MUST have the same media
type. Other dependencies relations expressed by SDP grouping have to
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be addressed in other specifications. A media description MUST NOT
be part of more than one group of the grouping type defined in this
specification.
5.2. Semantics
5.2.1. SDP grouping semantics for decoding dependency
This specification defines a new grouping semantic
Decoding Dependency "DDP":
DDP associates a media stream, identified by its mid attribute, with
a DDP group. Each media stream MUST be composed of an integer number
of Media Partitions. A media stream is identified by a session-
unique media format description (RTP payload type number) within a
media description. In a DDP group, all media streams MUST have the
same type of decoding dependency (as signaled by the attribute
defined in 5.2.2). All media streams MUST contain at least one
Operation Point. The DDP group type informs a receiver about the
requirement for handling the media streams of the group according to
the new media level attribute "depend", as defined in 5.2.2. .
When using multiple codecs, e.g. for Offer/Answer model, the media
streams MUST have the same dependency structure, regardless which
media format description (RTP payload type number) is used.
5.2.2. "depend" attribute for dependency signaling per media-stream
This memo defines a new media-level attribute, "depend", with the
following ABNF [RFC5234]. The identification-tag is defined in
[RFC3388]. In the following ABNF, fmt, token, SP, and CRLF are used
as defined in [RFC4566].
depend-attribute =
"a=depend:" dependent-fmt SP dependency-tag
*(";" SP dependent-fmt SP dependency-tag) CRLF
dependency-tag =
dependency-type *1( SP identification-tag ":"
fmt-dependency *("," fmt-dependency ))
dependency-type = "lay"
/ "mdc"
/ token
dependent-fmt = fmt
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fmt-dependency = fmt
dependency-tag, indicates one or more dependencies of one dependent-
fmt in the media description. These dependencies are signaled as
fmt-dependency values, which indicate fmt values of other media
descriptions. These other media descriptions are identified by their
identification-tag values in the depend-attribute. There MUST be
exactly one dependency-tag indicated per dependent-fmt.
dependent-fmt, indicates the media format description, as defined in
[RFC4566], that depends on one or more media format description in
the media description indicated by the value of identification-tag
within the dependency-tag.
fmt-dependency, indicates the media format description in the media
description identified by the identification-tag within the
dependency-tag, which the dependent-fmt of the dependent media
description depends on. In case a list of fmt-dependency values is
given, any element of the list is sufficient to satisfy the
dependency, at the choice of the decoding entity.
The depend-attribute describes the decoding dependency. The depend-
attribute MUST be followed by a sequence of dependent-fmt and the
corresponding dependency-tag fields which identify all related media
format descriptions in all related media descriptions of the
dependent-fmt. The attribute MAY be used with multicast as well as
with unicast transport addresses. The following dependency-types
values are defined in this memo:
o lay: Layered decoding dependency -- identifies the described media
stream as one or more Media Partitions of a layered Media
Bitstream. When "lay" is used, all media streams required for
decoding the Operation Point MUST be identified by identification-
tag and fmt-dependency following the "lay" string.
o mdc: Multi descriptive decoding dependency -- signals that the
described media stream is part of a set of a MDC Media Bitstream.
By definition, at least N out of M media streams of the group need
to be available to from an Operation Point. The values of N and M
depend on the properties of the Media Bitstream and are not
signaled within this context. When "mdc" is used, all required
media streams for the Operation Point MUST be identified by
identification-tag and fmt-dependency following the "mdc" string.
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Further dependency types MUST be defined in a standards-track
document.
6. Usage of new semantics in SDP
6.1. Usage with the SDP Offer/Answer Model
The backward compatibility in offer / answer is generally handled as
specified in [RFC3388], section 8.4, as summarized below.
Depending on the implementation, a node that does not understand DDP
grouping (either does not understand line grouping at all, or just
does not understand the DDP semantics) SHOULD respond to an offer
containing DDP grouping either (1) with an answer that ignores the
grouping attribute or (2) with a refusal to the request (e.g., 488
Not acceptable here or 606 Not acceptable in SIP).
In case (1), if the original sender of the offer still wishes to
establish communications, it SHOULD generate a new offer with a
single media stream that represents an Operation Point.
Note: in most cases, this will be the base layer of a layered Media
Bitstream, equally possible are Operation Points containing a set of
enhancement layers as long as all are part of a single media stream.
In case (2), if the sender of the original offer has identified that
the refusal to the request is caused by the use of DDP grouping, and
if the sender of the offer still wishes to establish the session, it
SHOULD re-try the request with an offer including only a single media
stream.
If the answerer understands the DDP semantics, it is necessary to
take the "depend" attribute into consideration in the offer/answer
procedure. The main rule for the "depend" attribute is that the
offerer decides the number of media streams and the dependency
between them. The answerer cannot change the dependency relations.
For unicast sessions where the answerer receives media, i.e. for
offers including media streams that have a directionality indicated
by "sendonly", "sendrecv" or have no directionality indicated, the
answerer MAY remove media operation points. The answerer MUST use the
dependency relations provided in the offer when sending media. The
answerer MAY send according to all of the operation points present in
the offer, even if the answerer has removed some of those operation
points. Thus an answerer can limit the number of operation points
being delivered to the answerer while the answerer can still send
media to the offerer using all of the operation points indicated in
the offer.
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For multicast sessions, the answerer MUST accept all operation points
and their related decoding dependencies or MUST remove non-accepted
operation points completely. Due to the nature of multicast, the
receiver can select which operation points, it actually receives and
processes. For multicast sessions that allow the answerer to also
send data, the answerer MAY send all of the offered operations
points.
In any case, if the answerer cannot accept one or more offered
operation points and/or the media stream's dependencies, the answerer
MAY re-invite with an offer including acceptable operation points
and/or dependencies.
Note: Applications may limit the possibilities to perform a re-
invite. The previous offer is also a good hint to the capabilities of
the other agent.
6.2. Declarative usage
If an RTSP receiver understands signaling according to this memo, it
SHALL setup all media streams that are required to decode the
Operation Point of its choice.
If an RTSP receiver does not understand the signaling defined within
this memo, it falls back to normal SDP processing. Two likely cases
have to be distinguished: (1) if at least one of the media types
included in the SDP is within the receiver's capabilities, it selects
among those candidates according to implementation specific criteria
for setup, as usual. (2) If none of the media type included in the
SDP can be processed, then obviously no setup can occur.
6.3. Usage with AVP and SAVP RTP profiles
The signaling mechanisms defined in this draft MUST NOT be used to
negotiate between using AVP [RFC3551] and SAVP [RFC3711] profile for
RTP. But both profiles MAY be used separately or jointly with the
signaling mechanism defined in this draft.
6.4. Usage with Capability Negotiation
This memo does not cover the interaction with Capability Negotiation
[I-D.ietf-mmusic-sdp-capability-negotiation]. This issue is for
further study and will be addressed in a different memo.
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6.5. Examples
a.) Example for signaling layered decoding dependency:
The example below shows a session description with three media
descriptions, all of type video and with layered decoding
dependency ("lay"). Each of the media description includes two
possible media format descriptions with different encoding
parameters as, e.g. "packetization-mode" (not shown in the
example) for the media subtypes "H264" and "H264-SVC" given by
the "a=rtpmap:"-line. The first media description includes two
H264 payload types as media format descriptions, "96" and "97",
as defined in [RFC3984] and represents the base layer operation
point (identified by "mid:L1"). The two other media
descriptions (identified by "mid:L2" and "mid:L3") include H264-
SVC payload types as defined in [I-D.ietf-avt-rtp-svc], which
contain enhancements to the base layer operation point or the
first enhancement layer operation point (media description
identified by "mid:L2").
Note: The SDP examples in [I-D.ietf-avt-rtp-svc] use numbers for
the mid values instead of using tokens like "L1", "L2" and "L3".
The example shows the dependencies of the media format
descriptions of the different media descriptions indicated by
"DDP" grouping, "mid" and "depend" attributes. The "depend"
attribute is used with the decoding dependency type "lay"
indicating layered decoding dependency. For example, the third
media description ("m=video 40004...") indentified by "mid:L3"
has different dependencies on the media format descriptions of
the two other media descriptions:
Media format description "100" depends on media format
description "96" or "97" of the media description indentified by
"mid:L1". This is an exclusive-OR, i.e. payload type "100" may
be used with payload type "96" or with "97", but one of the two
combinations is required for decoding payload type "100".
For media format description "101", it is different. This one
depends on two of the other media descriptions at the same time,
i.e. it depends on media format description "97" of the media
description indentified by "mid:L1" and it also depends on media
format description "99" of the media description indentified by
"mid:L2". For decoding media format description "101" both
media format description "97" and media format description "99"
are required by definition.
v=0
o=svcsrv 289083124 289083124 IN IP4 host.example.com
s=LAYERED VIDEO SIGNALING Seminar
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t=0 0
c=IN IP4 192.0.2.1/127
a=group:DDP L1 L2 L3
m=video 40000 RTP/AVP 96 97
b=AS:90
a=framerate:15
a=rtpmap:96 H264/90000
a=rtpmap:97 H264/90000
a=mid:L1
m=video 40002 RTP/AVP 98 99
b=AS:64
a=framerate:15
a=rtpmap:98 H264-SVC/90000
a=rtpmap:99 H264-SVC/90000
a=mid:L2
a=depend:98 lay L1:96,97; 99 lay L1:97
m=video 40004 RTP/AVP 100 101
b=AS:128
a=framerate:30
a=rtpmap:100 H264-SVC/90000
a=rtpmap:101 H264-SVC/90000
a=mid:L3
a=depend:100 lay L1:96,97; 101 lay L1:97 L2:99
b.) Example for signaling of multi descriptive decoding dependency:
The example shows a session description with three media
descriptions, all of type video and with multi descriptive
decoding dependency. Each of the media descriptions includes
one media format description. The example shows the
dependencies of the media format descriptions of the different
media descriptions indicated by "DDP" grouping, "mid" and
"depend" attributes. The "depend" attribute is used with the
decoding dependency type "mdc" indicating layered decoding
dependency. For example, media format description "104" in the
media description ("m=video 40000...") with "mid:M1" depends on
the two other media descriptions. It depends on media format
description "105" of media description with "mid:M2" and also
depends on media format description "106" of media description
with "mid:M3". In case of the multi descriptive decoding
dependency, media format description "105" and "106" can be used
by definition to enhance the decoding process of media format
description "104", but they are not required for decoding.
v=0
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o=mdcsrv 289083124 289083124 IN IP4 host.example.com
s=MULTI DESCRIPTION VIDEO SIGNALING Seminar
t=0 0
c=IN IP4 192.0.2.1/127
a=group:DDP M1 M2 M3
m=video 40000 RTP/AVP 104
a=mid:M1
a=depend:104 mdc M2:105 M3:106
m=video 40002 RTP/AVP 105
a=mid:M2
a=depend:105 mdc M1:104 M3:106
m=video 40004 RTP/AVP 106
a=mid:M3
a=depend:106 mdc M1:104 M2:105
7. Security Considerations
All security implications of SDP apply.
There may be a risk of manipulation the dependency signaling of a
session description by an attacker. This may mislead a receiver or
middle box, e.g. a receiver may try to compose a media bitstream out
of several RTP packet streams that does not form an Operation Point,
although the signaling made it believe it would form a valid
Operation Point, with potential fatal consequences for the media
decoding process. It is recommended that the receiver SHOULD perform
an integrity check on SDP and follow the security considerations of
SDP to only trust SDP from trusted sources.
8. IANA Considerations
The following contact information shall be used for all registrations
included here:
Contact: Thomas Schierl
mailto:mail@thomas-schierl.de
tel:+49-30-31002-227
The following semantics have been registered by IANA in Semantics for
the "group" SDP Attribute under SDP Parameters
http://www.iana.org/assignments/sdp-parameters.
Semantics Token Reference
------------------- ----- ---------
Decoding Dependency DDP RFC XXXX
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The SDP media level attribute "depend" has been registered by IANA in
Semantics for "att-field (media level only)". The registration
procedure in section 8.2.4 of [RFC4566] applies.
SDP Attribute ("att-field (media level only)"):
Attribute name: depend
Long form: decoding dependency
Type of name: att-field
Type of attribute: media level only
Subject to charset: no
Purpose: RFC XXXX
Reference: RFC XXXX
Values: see this document and registrations below.
The following semantics have been registered by IANA in Semantics for
the "depend" SDP Attribute under SDP Parameters:
Semantics of the "depend" SDP attribute:
Semantics Token Reference
---------------------------- ----- ---------
Layered decoding dependency lay RFC XXXX
Multi descriptive decoding dependency mdc RFC XXXX
New registrations for semantics of the "depend" SDP attribute are
added by the "Specification Required" policy as defined in [RFC5226].
9. Informative note on RFC 3388bis
Currently, there is ongoing work on [I-D.ietf-mmusic-rfc3388bis]. In
[I-D.ietf-mmusic-rfc3388bis], the grouping mechanism is extended in a
way that a media description can be part of more than one group of
the same grouping type in the same session description. However,
media descriptions grouped by this draft must be at most part of one
group of the type "DDP" in the same session description.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3388] Camarillo, G., Holler, J., and H. Schulzrinne, "Grouping of
Media Lines in the Session Description Protocol (SDP)",
RFC 3388, December 2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3551] Schulzrinne, H., and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551,
July 2003.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC4566] Handley, M., Jacobson, V, and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5226] Narten, T., and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP26, RFC5226, May
2008
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 5234, January 2008.
10.2. Informative References
[I-D.ietf-avt-rtp-svc]
Wenger, S., Wang Y.-K., T. Schierl and A. Eleftheriadis,
"RTP Payload Format for SVC Video",
draft-ietf-avt-rtp-svc-18 (work in progress), March
2009.
[I-D.ietf-mmusic-rfc3388bis]
Camarillo, G "The SDP (Session Description Protocol)
Grouping Framework",
draft-ietf-mmusic-rfc3388bis-02 (work in progress), January
2009.
[I-D.ietf-mmusic-sdp-capability-negotiation]
Andreasen, F., "SDP Capability Negotiation",
draft-ietf-mmusic-sdp-capability-negotiation-09, (work in
progress), July 2008.
[I-D.wang-avt-rtp-mvc]
Wang, Y.-K. and T. Schierl, "RTP Payload Format
for MVC Video", draft-wang-avt-rtp-mvc-03 (work in
progress), February 2009.
[MDC] Vitali, A., Borneo, A., Fumagalli, M., and R. Rinaldo,
"Video over IP using Standard-Compatible Multiple
Description Coding: an IETF proposal", Packet Video
Workshop, April 2006, Hangzhou, China.
[RFC3984] Wenger, S., Hannuksela, M., Stockhammer, T., Westerlund,M.,
and Singer, D., "RTP Payload Format for H.264 Video", RFC
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3984, February 2005.
Appendix A. Acknowledgements
Funding for the RFC Editor function is currently provided by the
Internet Society. Further, the author Thomas Schierl of Fraunhofer
HHI is sponsored by the European Commission under the contract number
FP7-ICT-214063, project SEA.
We want to also thank Magnus Westerlund, Joerg Ott, Ali Begen, Dan
Wing, Helmut Burklin, and Jean-Francois Mule for their valuable and
constructive comments to this memo.
Authors' Addresses
Thomas Schierl
Fraunhofer HHI
Einsteinufer 37
D-10587 Berlin
Germany
Phone: +49-30-31002-227
Email: mail@thomas-schierl.de
Stephan Wenger
Nokia
955 Page Mill Road
Palo Alto, CA, 94304
USA
Phone: +1-650-862-7368
Email: stewe@stewe.org
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s)
controlling the copyright in such materials, this document may not
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works of it may not be created outside the IETF Standards Process,
except to format it for publication as an RFC or to translate it
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