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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi Mike<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Perhaps the P-frame is really that big when sent from the
source?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’ve used Wireshark (http://www.wireshark.org/) to capture
the raw network packets, then go to “Statistics”, “RTP”,
“Analyse Streams...” to get an insight what the source is *<b>really</b>*
sending... E.g. it turns out that my source was sending flawless audio, but the
video stream had corrupted packets every now and then...<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Roland<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>PS: One way to rule out the “mash-together” theory
could be to have a look at the big P-frame with a hex-editor. Look for
sequences like 00 00 01 xx. These are start markers for MPEG-2. Make a list of
these markers and look them up in the MPEG-2 spec in regards to what they mean
(e.g. xx==b3 is sequence_header, xx==00 is picture_start, xx==01-af is
slice_start). If you see multiple picture starts or the same slice code repeat,
then indeed the frame is mashed together.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
live-devel-bounces@ns.live555.com [mailto:live-devel-bounces@ns.live555.com] <b>On
Behalf Of </b>mamille1@rockwellcollins.com<br>
<b>Sent:</b> Wednesday, July 30, 2008 7:58 AM<br>
<b>To:</b> live-devel@ns.live555.com<br>
<b>Subject:</b> [Live-devel] Very large P-frames in a recording<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>All</span> <br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>We're working
with an embedded system that receives an MPEG-2 transport stream from a TI DSP.
We've built an application that uses the live555 libraries to write this stream
out to disk. Every once in a while a very large P-frame, on the order of four
times the size of a typical P-frame in the stream, is written out to the file.
It's very intermittent -- it might happen once out of 6,000 frames. Has anyone
else seen this happen? We're beginning to dig into this. We're concerned that
our application might be mashing together several P-frames' worth of data, or
that we are not using the live555 library correctly. </span><br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I've reviewed
the last several months of the mailing list, but didn't see anything that
seemed relevant. </span><br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Thanks for your
help. </span><br>
<br>
<span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>-=- Mike Miller<br>
Rockwell Collins, Inc.<br>
Cedar Rapids, IA </span><o:p></o:p></p>
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