[Ffmpeg-devel] Mpeg-4 playback: issues with CBR padding

[Michael Niedermayer]

Hi

On Tue, Oct 31, 2006 at 05:10:04PM +0200, Itay Chamiel wrote:
> Hello,
>  
> I have stumbled into a case where an MPEG4 file is perfectly watchable
> using Quicktime Player or Mpegable, but is broken under VideoLAN and
> Mplayer, with complaints by ffmpeg.
>  
> I have uploaded it into upload.mplayerhq.hu/MPlayer/incoming/itayc . It
> is named "out.mp4" and is about 5MB in size. The video was encoded by
> the Prodys Mpeg-4 encoder running on a TI C64 DSP, and the result was
> encapsulated into MP4 format by the mp4creator program from the mpeg4ip
> package.
>  
> Normally, such a file plays well under anything, including ffmpeg based
> players. However, there is one case which breaks ffmpeg, and not other
> decoders: if the encoding is set to CBR at a high bitrate, so high that
> even at the highest quality setting the encoder has no choice but to pad
> the frames so they'll be large enough to fulfill the bitrate
> requirements. In this example, I encoded the Foreman 352x288 clip at 4
> Mbit, which is overkill and therefore most frames are padded. VideoLAN
> fails to decode most of it, with messages like:
>  
> ffmpeg warning: header damaged
> (mpeg4 at 00AF6360)
> ffmpeg warning: cannot decode one frame (6899 bytes)
> ffmpeg warning: slice end not reached but screenspace end (21511 left
> 004010, score= -52)
> (mpeg4 at 00AF6360)
> ffmpeg debug: concealing 396 DC, 396 AC, 396 MV errors
> (mpeg4 at 00AF6360)
> ffmpeg warning: header damaged
> (mpeg4 at 00AF6360)
> 
> ...and so on. I assume ffmpeg is supposed to be able to deal with this
> padding, but perhaps the padding created by this particular encoder is
> different in some way from other encoders.
> 
> I do understand that I'm supposed to get the latest SVN version before
> posting here, but I hope the group will bear with me, as compiling
> VideoLAN is no simple feat and I was hoping I could avoid it...
> 
> Anyway, the question is: Is this a problem with ffmpeg or with the
> encoder?

encoder, ffmpeg will ignore it and and decode the stream fine if you
specifiy -bug 16

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
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