No h263 Mode B support?

[walker]

It appears that Mode B support for h263 is not supported?

I have a h263 over RTP stream dump from a commercial videophone that includes both Mode A and Mode B.

From this thread on ffmpeg-devel, I'm taking it that only Mode A was ever supported?

 https://lists.libav.org/pipermail/ffmpeg-devel/2009-April/067074.html

I have tested the attached stream on four different commercial videophones. They all reproduce the video flawlessly. ffmpeg renders the Mode A packets, but simply prints out errors for the Mode B packets.

I am attaching three files:

demo.h263: The raw stream that is sent both to and from a videophone. H263 + RTP.

ffmpeg.out: The output from ffmpeg -i demo.h263 demo.mp4

demo.mp4: The ffmpeg-generated mp4 from the h263 stream. It seems that only the Mode A packets are interpreted by ffmpeg, so the video looks quite corrupted.

Sample error output from the attached+complete ffmpeg.out dump:

[h263 @ 0x7f86b083fc00] Bad picture start code
[h263 @ 0x7f86b083fc00] header damaged
[h263 @ 0x7f86b083fc00] I cbpy damaged at 20 0
[h263 @ 0x7f86b083fc00] Error at MB: 20
[h263 @ 0x7f86b083fc00] illegal ac vlc code at 0x14
[h263 @ 0x7f86b083fc00] Error at MB: 322
[h263 @ 0x7f86b083fc00] I cbpy damaged at 2 15
[h263 @ 0x7f86b083fc00] Error at MB: 347
[h263 @ 0x7f86b083fc00] I cbpy damaged at 1 5
[h263 @ 0x7f86b083fc00] Error at MB: 116
[h263 @ 0x7f86b083fc00] run overflow at 1x16 i:1
[h263 @ 0x7f86b083fc00] Error at MB: 369
[h263 @ 0x7f86b083fc00] illegal dc 128 at 0 5
[h263 @ 0x7f86b083fc00] run overflow at 1x5 i:1
[h263 @ 0x7f86b083fc00] Error at MB: 116
[h263 @ 0x7f86b083fc00] concealing 396 DC, 396 AC, 396 MV errors

[walker]

demo.h263 - Raw H263 RTP stream containing both mode a and b.

[walker]

ffmpeg-generated mp4 from demo.h263

[walker]

ffmpeg output while generating demo.mp4 from demo.h263

[cehoyos]

 http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/88232/focus=88245

[ggoodale]

I would agree that Mode B support for h263 decoding is not supported. Does any one know the complexity of modifying ituh263dec.c to support this mode ?