Re: [MMUSIC] FW: [rtcweb] How to signal RTX SSRCs with simulcast

Why would a redundancy RTP stream have an "a=rid" line of its own?  I am
struggling to find a use case for this.

On Thu, Jul 6, 2017 at 4:49 AM, Bo Burman <bo.burman@ericsson.com> wrote:

> To follow up on this, I suggest making the following addition to
> draft-ietf-mmusic-rid:
>
> ---- AFTER this text in section 4 ----
>
>    An "a=rid" SDP media attribute specifies restrictions defining a
>    unique RTP payload configuration identified via the "rid-id" field.
>    This value binds the restriction to the RTP Stream identified by its
>    RTP Stream Identifier SDES item [I-D.ietf-avtext-rid].  To be clear,
>    implementations that use the "a=rid" parameter in SDP MUST support
>    the RtpStreamId SDES item described in [I-D.ietf-avtext-rid].  Such
>    implementations MUST send it for all streams in an SDP media
>    description ("m=") that have "a=rid" lines remaining after applying
>    the rules in Section 6 and its subsections.
>
> ---- ... add this proposed, new text ----
>
>    Implementations that use the "a=rid" parameter in SDP and that
>    make use of redundancy RTP streams [RFC7656], e.g. RTP RTX
>    [RFC4588] or FEC [RFC5109][I-D.ietf-payload-flexible-fec-scheme],
>    for any of the source RTP streams that have "a=rid" lines remaining
>    after applying the rules in Section 6 and its subsections, MUST
>    support and use RepairedRtpStreamId SDES item described in
>    [I-D.ietf-avtext-rid] for those redundancy RTP streams. This provides
>    the binding between the source RTP stream and the corresponding
>    redundancy RTP stream, by setting RepairedRtpStreamId value for
>    the redundancy RTP stream to the RtpStreamId value of the source
>    RTP stream. The redundancy RTP stream MAY (but need not) have an
>    "a=rid" line of its own, in which case the RtpStreamId SDES item value
>    will be different from the corresponding source RTP stream.
>
> ---- End changes ----
>
> The -simulcast draft would be entirely agnostic to this clarification of
> "a=rid" and RepairedRtpStreamId usage and thereby transparently allow using
> redundancy RTP streams with simulcast.
>
> /Bo
> (as individual)
>
> > -----Original Message-----
> > From: Iñaki Baz Castillo [mailto:ibc@aliax.net]
> > Sent: den 13 mars 2017 14:43
> > To: Bo Burman <bo.burman@ericsson.com>
> > Cc: mmusic (mmusic@ietf.org) <mmusic@ietf.org>; Taylor Brandstetter (
> deadbeef@google.com)
> > <deadbeef@google.com>; draft-ietf-mmusic-rid@ietf.org;
> draft-ietf-mmusic-sdp-simulcast@ietf.org
> > Subject: Re: [MMUSIC] FW: [rtcweb] How to signal RTX SSRCs with simulcast
> >
> > 2017-03-13 14:41 GMT+01:00 Bo Burman <bo.burman@ericsson.com>:
> > > [BoB] Usage of RepairedRtpStreamId and RtpStreamId are already defined
> on RTP level by -avtext-rid. If we have
> > preferences on how to best use them with redundancy RTP streams in
> general, I suggest we add text to -mmusic-rid
> > about it. This would be regardless if we go for option A or B, but
> decided once and for all, thus applicable to RFC 4588 rtx
> > and FLEX-FEC alike.
> >
> > Agreed.
> >
> >
> > --
> > Iñaki Baz Castillo
> > <ibc@aliax.net>
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