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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1157/">https://reviewboard.asterisk.org/r/1157/</a>
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<a href="https://reviewboard.asterisk.org/r/1157/diff/2/?file=16038#file16038line285" style="color: black; font-weight: bold; text-decoration: underline;">/funcs/func_jitterbuffer.c</a>
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(Diff revision 2)
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<td colspan="2"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="k">static</span> <span class="kt">int</span> <span class="nf">jb_helper</span><span class="p">(</span><span class="k">struct</span> <span class="n">ast_channel</span> <span class="o">*</span><span class="n">chan</span><span class="p">,</span> <span class="k">const</span> <span class="kt">char</span> <span class="o">*</span><span class="n">cmd</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">data</span><span class="p">,</span> <span class="k">const</span> <span class="kt">char</span> <span class="o">*</span><span class="n">value</span><span class="p">)</span></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="p">{</span></pre></td>
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<pre style="margin-left: 2em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">One complication I am dealing with is how to handle the fact that a user could place a jitter buffer on both the read and the write side of the channel. I think I should add a check at the beginning of this function to detect if a write jitter buffer is present on the channel, and if so exit.</pre>
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<p>- David</p>
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<p>On March 31st, 2011, 5:29 p.m., David Vossel wrote:</p>
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<div>Review request for Asterisk Developers.</div>
<div>By David Vossel.</div>
<p style="color: grey;"><i>Updated 2011-03-31 17:29:42</i></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This patch allows a jitterbuffer to be placed on the read side of a channel using a dialplan function.
I accomplished this by using framehooks (awesomehooks) to capture audio frames in the read direction of a channel. As frames enter into the framehook callback two things may occur.
1. If the frame is audio, it is placed into the jitterbuffer and then converted to a null frame.
2. If the frame either comes in as a null frame, or is converted from audio to a null frame, the jitter buffer is checked to see if a frame is ready to be released. If this is the case, the null frame is replaced by the next available dejittered frame from the jitterbuffer queue.
Frames are guaranteed to be released at a consistent interval through the use of a timer. The channel listens to this timer's fd causing read to get called each time the timer fires. Read will get called more often that usual with a jitterbuffer on the channel, but frames will not be released until the right delivery time is met.
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">I tested this by creating simulated network delay with netem. Delay was set to vary between 200ms-100ms and packets were set to vary in the order they were sent.
A call coming in on the network with delay enters a meetme conference and plays back a file. Another phone is used to connect to that meetme conference without the simulated delay to hear the effect of the network on audio quality. Without the jitterbuffer enabled on the playback channel, the audio being played into the conference sounds terrible. With either an adaptive or fixed jitterbuffer set at at least 200ms in size the audio sounds perfect.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>/trunk/funcs/func_jitterbuffer.c <span style="color: grey">(PRE-CREATION)</span></li>
<li>/trunk/include/asterisk/abstract_jb.h <span style="color: grey">(312069)</span></li>
<li>/trunk/include/asterisk/channel.h <span style="color: grey">(312069)</span></li>
<li>/trunk/main/abstract_jb.c <span style="color: grey">(312069)</span></li>
<li>/trunk/main/channel.c <span style="color: grey">(312069)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/1157/diff/" style="margin-left: 3em;">View Diff</a></p>
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