Subject: [siprec] siprec & RTCP

From: Randell Jesup <[email-masked]>
Date: Sun, 24 Jul 2011 11:51:28 -0400

With regards to http://tools.ietf.org/html/draft-eckel-siprec-rtp-rec-01

It's stated in 6. that:
    Therefore, it is RECOMMENDED
    that the SRC and SRS not rely entirely on SAVPF or AVPF for core
    functionality that may be at least partially achievable using SAVP
    and AVP.

and

    12. RTCP Feedback Messages

    "Codec Control Messages in the RTP Audio-Visual Profile with Feedback
    (AVPF)" [RFC5104] specifies extensions to the messages defined in
    AVPF [RFC4585].  Support for and proper usage of these messages is
    important to SRC and SRS implementations.  Note that these messages
    are applicable only when using the AVFP or SAVPF RTP profiles.

But then it states that using FIR is "disallowed" for recovery from
errors (is it allowed for other reasons?) and it then states:

    12.2. Picture Loss Indicator

    Using the FIR command to recover from errors is explicitly
    disallowed, and instead the PLI message defined in AVPF [RFC4585]
    SHOULD be used.  The PLI message reports lost pictures and has been
    included in AVPF for precisely that purpose.

However, this conflicts with the statement above that SAVP and AVP are
allowed.

Also, what is the reason for describing the size of a IDR in response to 
a FIR if they're "disallowed"?  What is the purpose of describing
it here anyways?

(I don't read siprec; cc me on any responses - I hang out in
AVTcore/etc)

-- 
Randell Jesup
[email-masked]

---

From: "Charles Eckel (eckelcu)" <[email-masked]>
Date: Mon, 25 Jul 2011 11:00:35 -0700

Hi Randell,

Thanks for having a look at the draft. Your question is similar to one
raised by Roni. FIR should be used as defined in RFC 5104, but only for
the things for which it is appropriate. For example, FIR is appropriate
for scene change resulting from active speaker video switching. On the
other hand, using the FIR command to recover from errors is explicitly
disallowed in RFC 5104. Instead the PLI message defined in AVPF
[RFC4585] should be used.
Hopefully that explains the apparent contradiction in the draft. If not,
let me know. Perhaps I am still missing something.

Cheers,
Charles

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
Behalf Of Randell Jesup
> Sent: Sunday, July 24, 2011 11:51 AM
> To: [email-masked]
> Subject: [siprec] siprec & RTCP
> 
> With regards to
http://tools.ietf.org/html/draft-eckel-siprec-rtp-rec-01
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