[Ffmpeg-devel] trouble with h264.c

[Måns Rullgård]

Scott Treude <scott at niceshoes.com> writes:

> On Friday, May 13, 2005 10:41 AM, M?ns Rullg?rd <mru at inprovide.com> wrote:
>>Scott Treude <scott at niceshoes.com> writes:
>>
>>> Hello,
>>>
>>> I'm trying to convert an h264 quicktime to a series of ppm files and
>>> I'm receiving the following error:
>>>
>>> ffmpeg: h264.c:2316: mc_dir_part: Assertion `pic->data[0]' failed.
>>>
>>> The command I'm using is:
>>> /usr/local/bin/ffmpeg -ss 100  -t .2 -i myMovie.mov test%d.ppm
>>>
>>> It seems to work fine without the -ss; so is seeking a problem with h264?
>>
>>This is a know problem, at least to me.  Unfortunately, I'm not sure
>>how to fix it.  The problem is that a reference picture used by the
>>picture being decoded is unavailable, since it was before the point
>>you started decoding at.
>>
>>Michael, Loren, what should we do about this?  It used to work, a long
>>time ago.  IIRC, it broke around the time B-frame support was
>>added.
>
> thanks for the insight.  Wouldn't that be a problem with other
> codec's as well (like mpeg2)?

The mpeg2 decoder seems to handle it, one way or another.

> I assume that the reference picture is used to create the pictures
> (frames?) following it.  Is there a way to go backwards to the
> nearest reference pic to retrieve it and then jump forward to create
> the desired pictures?

If the container flags the key frames, you can do this.  It's not the
business of libavcodec, though.

-- 
M?ns Rullg?rd
mru at inprovide.com