[Ffmpeg-devel] -vcodec copy h264 from mp4 to avi weirdness

[Loren Merritt]

On Sun, 18 Jun 2006, M?ns Rullg?rd wrote:

> Something strange happens when copying h264 video from mp4 format to
> avi.  The output file simply will not decode with ffmpeg if lavf is
> used for demuxing.  Instead, lots of errors are printed:
>
> [h264 @ 0xb7ecf188]top block unavailable for requested intra mode at 4 0
> [h264 @ 0xb7ecf188]error while decoding MB 4 0, bytestream (3093)
> [h264 @ 0xb7ecf188]top block unavailable for requested intra mode at 33 5
> [h264 @ 0xb7ecf188]error while decoding MB 33 5, bytestream (12960)
> [h264 @ 0xb7ecf188]top block unavailable for requested intra4x4 mode -1 at 20 5
> [h264 @ 0xb7ecf188]error while decoding MB 20 5, bytestream (3311)
> [h264 @ 0xb7ecf188]top block unavailable for requested intra mode at 32 5
> [h264 @ 0xb7ecf188]error while decoding MB 32 5, bytestream (1717)
> ... lots more of the same stuff...
>
> TCVP and xine both play the file properly with their native avi
> demuxers.  TCVP with lavf fails.
>
> This happens with every sample I've tried.  NeroAVC.mp4 in the mplayer
> samples collection is one of them.  Copying the video to a new mp4
> file works fine.
>
> Does anyone have an idea what could be causing this?

Because h264 is one of those brain-damaged formats that has different 
encodings depending on which container it's in?
MP4 and MKV use the AVC1 encoding (length-prefix), AVI, ES, and TS use the 
Annex B encoding (startcodes).

--Loren Merritt