[Live-devel] MPEG-4 Visual configuration bits in SDP

[Ross Finlayson]

>I would disagree that decoding SDP config bits is not needed for 
>streaming at all.
>
>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.
>
>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.

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".)
-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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