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RTP matching rules #681

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RTP matching rules #681

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64617b7
RTP matching rules
aboba Apr 18, 2017
1a1427c
Align PT table construction with BUNDLE algorithm
aboba Apr 18, 2017
3bae28d
RTP routing rule update
aboba Apr 18, 2017
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137 changes: 71 additions & 66 deletions index.html
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Expand Up @@ -4398,8 +4398,16 @@ <h3>RTP matching rules</h3>
the packet to, based on the values of the SSRC and payload type fields in the RTP
header, as well as the value of the <a>MID</a> RTP header extension, if
present.</p>
<p>Applications can implement RTP stacks in different ways. Within Sections
8.3.1, 8.3.2 and 13.4, algorithms are provided that are based on
the RTP/RTCP packet routing behavior described in [[!BUNDLE]] Section 10.2.
However, this material is not meant to prescribe exactly how the RTP
stack is implemented. Implementations MAY use any algorithms that
achieves equivalent results to those described in [[!BUNDLE]] Section 10.2.</p>
<section id="tablefilling*">
<h3>Table maintenance</h3>
<p>The <code><a>RTCRtpListener</a></code> maintains three tables in order to
facilitate matching: the <code>ssrc_table</code> which maps SSRC values to
facilitate RTP packet routing: the <code>ssrc_table</code> which maps SSRC values to
<code><a>RTCRtpReceiver</a></code> objects; the <code>muxId_table</code> which maps
values of the <a>MID</a> header extension to <code><a>RTCRtpReceiver</a></code>
objects and the <code>pt_table</code> which maps payload type values to
Expand All @@ -4409,75 +4417,72 @@ <h3>RTP matching rules</h3>
is called, and are removed when <code>receiver.stop()</code> is called. If
<code>receiver.receive(<var>parameters</var>)</code> is called again, all entries
referencing <var>receiver</var> are removed prior to adding new entries.</p>
<p>muxId table:<p>
<ol>
<li>If <code><var>parameters</var>.muxId</code> is set,
<code>muxId_table[<var>parameters</var>.muxId]</code> is set to <var>receiver</var>.</li>
<li>If <code>muxId_table[<var>muxId</var>]</code> is already set to a value other than
<var>receiver</var>, then <code>receiver.receive()</code> will be rejected with
<code>InvalidParameters</code>.</li>
</ol>
<p>SSRC table:</p>
<ol>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].rtx.ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].rtx.ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].fec.ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].fec.ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>If <code>ssrc_table[<var>ssrc</var>]</code> is already set to a value other
than <var>receiver</var>, then <code>receiver.receive()</code> will be rejected
with <code>InvalidParameters</code>.</li>
</ol>
<p>payload type table:<p>
<ol>
<li>If <code><var>parameters</var>.muxId</code> is set, abort these steps.</li>
<li>If <code><var>parameters</var>.encodings[<var>i</var>].ssrc</code> is unset for all
values of <var>i</var> from 0 to <code>encodings.length-1</code>, then add
entries to <code>pt_table</code> by setting
<code>pt_table[<var>parameters</var>.codecs[<var>j</var>].payloadType]</code> to
<var>receiver</var>, for values of <var>j</var> from 0 to <code>codecs.length-1</code>.</li>
<li>If <code>pt_table[<var>pt</var>]</code> is already set to a value other than
<var>receiver</var> then <code>receiver.receive()</code> will be rejected with
<code>InvalidParameters</code>.</li>
</ol>
<p>To prepare for demultiplexing RTP packets to the correct
<code><a>RTCRtpReceiver</a></code> the following steps MUST be followed:</p>
<b>muxId table construction</b>
<ol>
<li>If <code><var>parameters</var>.muxId</code> is set,
<code>muxId_table[<var>parameters</var>.muxId]</code> is set to <var>receiver</var>.</li>
<li>If <code>muxId_table[<var>muxId</var>]</code> is already set to a value other than
<var>receiver</var>, then <code>receiver.receive()</code> will be rejected with
<code>InvalidParameters</code>.</li>
</ol>
<b>SSRC table construction</b>
<ol>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].rtx.ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].rtx.ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>Set <code>ssrc_table[<var>parameters</var>.encodings[<var>i</var>].fec.ssrc]</code>
to <var>receiver</var> for each entry where
<code><var>parameters</var>.encodings[<var>i</var>].fec.ssrc</code> is set, for values of
<var>i</var> from 0 to <code>encodings.length-1</code>.</li>
<li>If <code>ssrc_table[<var>ssrc</var>]</code> is already set to a value other
than <var>receiver</var>, then <code>receiver.receive()</code> will be rejected
with <code>InvalidParameters</code>.</li>
</ol>
<b>Payload Type table construction</b>
<ol>
<li>Set <code>pt_table[<var>parameters</var>.codecs[<var>j</var>].payloadType]</code> to
<var>receiver</var>, for values of <var>j</var> from 0 to <code>codecs.length-1</code>.</li>
<li>If <code>pt_table[<var>pt</var>]</code> is already set to a value other than
<var>receiver</var> then set <code>pt_table[<var>pt</var>]</code> to null.</li>
</ol>
</section>
<section id="rtppackethandling*">
<h4>RTP packet handling</h4>
<p>When an RTP packet arrives, the implementation determines the
<code><a>RTCRtpReceiver</a></code> <var>rtp_receiver</var> to send it to as
follows:
<ol>
<li>If <var>packet.muxId</var> is set: If
<code>muxId_table[<var>packet.muxId</var>]</code> is unset, fire the
<code><a>unhandledrtp</a></code> event, else set <var>rtp_receiver</var> to
<code>muxId_table[<var>packet.muxId</var>]</code> and check whether the value of
<var>packet.pt</var> is equal to one of the values of
<p>For each RTP packet received, the following steps MUST be followed
to route the RTP packet <var>packet</var> to the correct
<code><a>RTCRtpReceiver</a></code> <var>rtp_receiver</var>.
Note that the phrase "deliver a packet to <var>rtp_receiver</var>'
means to further process the packet as would normally happen with RTP/RTCP,
including firing the <code><a>unhandledrtp</a></code> event if the packet's
payload type does not match any payload type configured for
<var>rtp_receiver</var>. This is determined by checking whether
<var>packet.pt</var> is equal to any of the values of
<code><var>parameters</var>.codecs[<var>j</var>].payloadtype</code> for the
<code><a>RTCRtpReceiver</a></code> object <var>rtp_receiver</var>, where
<var>j</var> varies from 0 to <code>codecs.length-1</code>. If so, set
<code>ssrc_table[<var>packet.ssrc</var>]</code> to <var>rtp_receiver</var> and route
the packet to <var>rtp_receiver</var>. If <var>packet.pt</var> does not match, fire
the <code><a>unhandledrtp</a></code> event.</li>
<li>Else if <code>ssrc_table[<var>packet.ssrc</var>]</code> is set: set
<var>rtp_receiver</var> to <code>ssrc_table[<var>packet.ssrc</var>]</code>
and check whether the value of <var>packet.pt</var> is equal to one of the
values of <code><var>parameters</var>.codecs[<var>j</var>].payloadtype</code>
for <var>rtp_receiver</var>, where <var>j</var> varies from 0 to
<code>codecs.length-1</code>. If so, route the packet to <var>rtp_receiver</var>.
If <var>packet.pt</var> does not match, fire the <code><a>unhandledrtp</a></code> event.</li>
<li>Else if <code>pt_table[<var>packet.pt</var>]</code> is set: set
<var>rtp_receiver</var> to <code>pt_table[<var>packet.pt</var>]</code>, set
<code>ssrc_table[<var>packet.ssrc</var>]</code> to <var>rtp_receiver</var>
and route the packet to <var>rtp_receiver</var>.</li>
<li>Else if no matches are found in the <code>ssrc_table</code>,
<code>muxId_table</code> or <code>pt_table</code>, fire the
<code><a>unhandledrtp</a></code> event.</li>
<var>j</var> varies from 0 to <code>codecs.length-1</code>.
<ol>
<li>If <var>packet.muxId</var> is set and
<code>muxId_table[<var>packet.muxId</var>]</code> is unset, fire the
<code><a>unhandledrtp</a></code> event and stop.</li>
<li>If <var>packet.muxId</var> is set and the packet's extended
sequence number is greater than that of the last MID update, as discussed
in [[RFC7941]] Section 4.2.6, set <code>ssrc_table[<var>packet.ssrc</var>]</code>
to <code>muxId_table[<var>packet.muxId</var>]</code>.</li>
<li>If <code>ssrc_table[<var>packet.ssrc</var>]</code> is set, set
<var>rtp_receiver</var> to <code>ssrc_table[<var>packet.ssrc</var>]</code> and
deliver the packet to <var>rtp_receiver</var>.</li>
<li>If <code>pt_table[<var>packet.pt</var>]</code> is set, set
<var>rtp_receiver</var> and <code>ssrc_table[<var>packet.ssrc</var>]</code>
to <code>pt_table[<var>packet.pt</var>]</code> and deliver the packet
to <var>rtp_receiver</var>.</li>
<li>Otherwise, fire the <code><a>unhandledrtp</a></code> event.</li>
</ol>
</section>
</section>
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