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--></style><title>Re: [Live-devel] MPEG-4 Visual configuration bits
in SDP</title></head><body>
<blockquote type="cite" cite><font face="Arial" size="-1">I would
disagree that decoding SDP config bits is not needed for streaming at
all.</font></blockquote>
<blockquote type="cite" cite> </blockquote>
<blockquote type="cite" cite><font face="Arial" size="-1">For example,
Axis 240S and 240Q video servers *do not* provide "x-dimensions"
parameter in their SDP (or other similar parameters
like "cliprect" or "framesize"). Thus,
LIVE555 is not aware about video resolution when recording RTSP from
these video servers. The width and height values must be supplied
manually, which is not feasible in some cases. E.g. when
recording MPEG-4 stream to AVI file, the wrong width and height
values in AVI header might result in unplayable
file.</font></blockquote>
<blockquote type="cite" cite> </blockquote>
<blockquote type="cite" cite><font face="Arial" size="-1">From another
hand, Axis 240S and 240Q video servers provide the required video
resolution info in bits "video_object_layer_width" and
"video_object_layer_height" from config parameter.
Thus, config bits parsing/decoding would be a useful
feature in LIVE555. The decoding algorythm is pretty simple and can be
found in ISO/IEC 14496 Part 2 documentation in "Visual bitstream
syntax" chapter.</font></blockquote>
<div><br></div>
<div>Yes, for that specific purpose - extracting width and height
information - I can see how it could be useful to have code that
analyzes the MPEG-4 Video config data. (In turns out that - for
transmitting MPEG-4 Elementary Stream files - we already do a bit of
parsing of the "VOL header" structure in
"MPEG4VideoStreamFramer", in order to extract the
"vop_time_increment_resolution".)</div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div><br>
Ross Finlayson<br>
Live Networks, Inc.<br>
http://www.live555.com/</div>
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