RE: [AVT] RE: [MMUSIC] questions about grouping media streams in RTP andSDP (RFC3388 etc), advice needed

[Dave Singer <[e-mail]>]

At 10:40  -0700 7/06/07, Thomas Schierl wrote:
>Hi Dave,
>
>I think there is a strong relation of your problem and the
>http://tools.ietf.org/wg/mmusic/draft-schierl-mmusic-layered-codec-03.txt .
>In this draft, we described media dependency in general, not only for
>scalable video. Currently, two types of dependencies are defined: layered
>and mdc assuming the media is partially transported in different RTP
>sessions. It would be easy to integrate your needs, if they should not be
>already covered.
>
>
>Thomas

Thank you.  I agree the problems are identical, or close to it.

Do you think we should use 'lay' or 'mdc', or a new dependency type? 
Or integrate a new group type into the draft (is 'DDP' right for our 
application)?

>
>>  -----Original Message-----
>>  From: Dave Singer [mailto:[e-mail]]
>>  Sent: Tuesday, June 05, 2007 8:34 AM
>>  To: Even, Roni; mmusic; IETF AVT WG
>>  Cc: Clinton Priddle (KI/EAB)
>>  Subject: [AVT] RE: [MMUSIC] questions about grouping media streams in RTP
>>  andSDP (RFC3388 etc), advice needed
>>
>>  At 10:03  +0300 5/06/07, Even, Roni wrote:
>>  >Dave,
>>  >For layered encoding there is a proposal for a new grouping attribute in
>>  >http://tools.ietf.org/wg/mmusic/draft-schierl-mmusic-layered-codec-03.tx
>>  >t
>>
>>  I don't think this is a layered coding issue, either, alas.
>>
>>  >I looked at RFC3388 and I think that FID is not the answer to your
>>  >requirement as you mentioned
>>  >
>>  >To me it looks like what you are looking for is a way to specify
>>  >alternate offers.
>>
>>  No, these streams are not alternatives to each other in the regular
>>  sense.  Nor is this really used in offer/answer;  it's more an issue
>>  for multicast.  In multicast, you open the tune-in stream and the
>>  base stream, grab the first I-frame that arrives (in either) and then
>>  drop the tune-in stream.
>>
>>  Yes, we're aware that the recipient needs to be able to tell which is
>>  the base and which is the tune-in.
>>
>>  >If this is the case I have similar requirements and
>>  >would be happy to support such work.
>>  >
>>  >You also need a way to give semantics to the "repair" stream, this can
>>  >be done based on the content attribute from RFC 4796 or using a
>>  >dependency attribute see in Schierl's draft. The mid tag is not enough
>>  >for the receiver to know what you meant by this offer and which stream
>>  >is the repair.
>>  >
>>  >Here is an example for a solution using a new Alternatives grouping
>>  >attribute and giving semantics to the repair stream
>>  >
>>  >By using the grouping attribute in the offer you can know if the
>>  >answerer understood the grouping since if he does not than he will send
>>  >an answer with no a=group
>>  >
>>  >v=0
>>  >o=bob 280744730 28977631 IN IP4 host.example.com
>>  >s=
>>  >t=0 0
>>  >
>>  >a=group:ALTS 1 2
>>  >a=group:ALTS 1 3
>>  >
>>  >m=audio 6886 RTP/AVP 0
>>  >c=IN IP6 2001:0600::1
>>  >a=mid:1
>>  >
>>  >m=video 9000 RTP/AVP 100
>>  >c=IN IP4 192.0.2.2
>>  >a=rtpmap:100 H263-1998
>>  >a=mid:2
>>  >
>>  >m=video 9002 RTP/AVP 101
>>  >c=IN IP4 192.0.2.2
>>  >a=rtpmap:101 H263-1998
>>  >a=mid:3
>>  >a=content:repair=2 or a=depend:repair=2
>>  >
>>  >
>>  >Roni Even
>>  >
>>  >>  -----Original Message-----
>>  >>  From: Dave Singer [mailto:[e-mail]]
>>  >>  Sent: Monday, June 04, 2007 7:19 PM
>>  >>  To: mmusic; IETF AVT WG
>>  >>  Cc: Clinton Priddle (KI/EAB)
>>  >>  Subject: [MMUSIC] questions about grouping media streams in RTP and
>>  >SDP
>>  >>  (RFC3388 etc), advice needed
>>  >>
>>  >>  Hi
>>  >>
>>  >>  we have a need to group together two media streams, in the style of
>>  >RFC
>>  >>  3388 <http://www.ietf.org/rfc/rfc3388.txt> but we're unsure whether an
>>  >>  existing group type is suitable or not, and if it's not, we'd like to
>>  >>  agree on a new one, and document it (presumably in an RFC).
>>  >>
>>  >>  What we have is a normal media stream, and a separate 'repair' or
>  > >>  'entry' stream, that can be used when tuning in, or after loss, but is
>>  >>  otherwise un-needed.  An example might be a video stream with a low
>>  >>  I-frame interval (say every 15 seconds), with a repair stream which
>>  >has
>>  >>  only I-frames that are equivalent to the time-parallel non-I frame, at
>>  >a
>>  >>  frequency of say 1 per second.
>>  >>
>>  >>  It's not clear to us whether this is "one media flow" in the sense of
>>  >>  FID, or not.  The example offers AMR and GSM audio, which are
>>  >>  alternatives, and DTMF tones along with audio, which are supplementary
>>  >>  to each other.  Perhaps we fall afoul of this restriction:
>>  >>
>>  >>  "An application that encodes the same media using different codecs
>>  >>  simultaneously MUST NOT use FID to group those media lines."
>>  >>
>>  >>  or this one, for layered encoding:
>>  >>
>>  >>  "FID MUST NOT be used to group "m" lines that do not represent the
>>  >same
>>  >>  information."  (Though how DTMF tones and their associated audio pass
>>  >>  this test is not clear).
>>  >>
>>  >>  Nor is it clear that the FEC group of RFC 4756 is right, either.  For
>>  >a
>>  >>  start, we may wish to use this new ID in combination with FEC, and
>>  >>  secondly this tune-in stream has different characteristics.  For
>>  >>  example, one can typically ignore all FEC and (as long as there are no
>>  >>  errors) decode the stream correctly.  Ignoring the tune-in stream
>>  >  > entirely may mean that you will never find a tune-in point, making
>>  the
>>  >>  normal stream useless.
>>  >>
>>  >>  So, can we use FID for associating a repair stream with its base (we
>>  >tag
>>  >>  the streams so we know which is which, of course)?
>>  >>
>>  >>  p.s. RFC 4756 claims in the IANA section that the FEC group is
>>  >>  registered under SDP characteristics, but actually I can find no
>>  >>  registry anywhere in IANA of group types.
>>  >>
>>  >>
>>  >>  --
>>  >>  David Singer
>>  >>  Apple/QuickTime
>>  >>
>>  >>  _______________________________________________
>>  >>  mmusic mailing list
>>  >>  [e-mail]
>>  >>  https://www1.ietf.org/mailman/listinfo/mmusic
>>
>>
>>  --
>>  David Singer
>>  Apple/QuickTime
>>
>>  _______________________________________________
>>  Audio/Video Transport Working Group
>>  [e-mail]
>>  https://www1.ietf.org/mailman/listinfo/avt


-- 
David Singer
Apple/QuickTime

_______________________________________________
Audio/Video Transport Working Group
[e-mail]
https://www1.ietf.org/mailman/listinfo/avt