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On 11/16/2011 09:36 AM, Colin Perkins wrote:
<blockquote
cite="mid:45AA6AFB-832D-4D6E-85D8-69A12900CC0D@csperkins.org"
type="cite">[catching up]
<div><br>
<div>
<div>On 31 Oct 2011, at 08:50, Harald Alvestrand wrote:</div>
<blockquote type="cite">
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http-equiv="Content-Type">
<div bgcolor="#ffffff" text="#000000"> On 10/30/2011 02:38
PM, Justin Uberti wrote:
<blockquote
cite="mid:CAOJ7v-0uQ7__UouKKNp_2WAO1xzor_t5c2Ktc-pThDVgtf_myw@mail.gmail.com"
type="cite">In Appendix A, minor error in the diagram
for the extension. The second 0xBE should be 0xDE.
<div>
<pre style="word-wrap: break-word; white-space: pre-wrap;"> 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xBE | 0xBE | length=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID | len=2 | send timestamp (t_i) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</pre>
<pre style="word-wrap: break-word; white-space: pre-wrap;"><span class="Apple-style-span" style="font-family: arial; white-space: normal;">For the REMB message, what do we expect the "SSRC of packet sender" header field to be set to? Is it just an arbitrary choice of any of the SSRCs used by the sender of the REMB?</span></pre>
</div>
</blockquote>
Apparently one of Magnus' new drafts goes into that
territory. I suspect Colin Perkins will have opinions too.<br>
<br>
I think that for efficiency and general sanity, these need
to be sent from one of the SSRCs and not from all of the
SSRCs. I don't see any reason not to pick one at random.<br>
</div>
</blockquote>
</div>
<div apple-content-edited="true"><span class="Apple-style-span"
style="border-collapse: separate; color: rgb(0, 0, 0);
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class="Apple-style-span" style="border-collapse:
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class="Apple-style-span" style="border-collapse:
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class="Apple-style-span" style="border-collapse:
separate; color: rgb(0, 0, 0); font-family: 'Lucida
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<div><br>
</div>
<div>I can imagine there are scenarios where you'd
want to congestion control each stream
individually, and have a receiver partition up its
available bandwidth estimate between them. In that
case, you'd send per-SSRC. </div>
<div><br>
</div>
<div>If you want to control a group of streams, then
signalling a single SSRC, and making assumptions
about which other SSRCs it applies to, doesn't
make sense to me. It would be clearer, and more
future proof, to define an identifier for the
group of streams, signal that in SDP, and report
that identifier in the feedback messages. </div>
<div><br>
</div>
<div>That is, be explicit, rather than implicitly
trying to group things based on assumptions about
which set of SSRCs should be controlled together.<br
class="Apple-interchange-newline">
</div>
</span></span></span></span></span></div>
</div>
</blockquote>
As described, the feedback option explicitly lists the SSRCs it
applies to:<br>
<br>
<tt> 0 1 2
3<br>
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
1<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
|V=2|P| FMT=15 | PT=206 | length
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| SSRC of packet sender
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| SSRC of media source
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| Unique identifier 'R' 'E' 'M' 'B'
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| Num SSRC | BR Exp | BR Mantissa
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| SSRC feedback
|<br>
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<br>
| ...
|<br>
<br>
</tt>The discussion has only focused on the "SSSRC of packet sender"
field.<br>
<br>
The timestamp option diagrammed at the beginning of this thread
will, of course, only apply to the packet it occurs in.<br>
<br>
<br>
<br>
<br>
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