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

["Thomas Schierl" <[e-mail]>]

Hi Dave,

I think the grouping type DDP fits, but we should talk about an extra type
of dependency for that. 

Thomas



> -----Original Message-----
> From: Dave Singer [mailto:[e-mail]]
> Sent: Thursday, June 07, 2007 10:49 AM
> To: Thomas Schierl
> Cc: [e-mail]; [e-mail]; 'Even, Roni'; [e-mail]
> Subject: RE: [AVT] RE: [MMUSIC] questions about grouping media streams
> inRTP andSDP (RFC3388 etc), advice needed
> 
> 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


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