[FFmpeg-devel] [PATCH 7/7] Add check in av_write_header() which validates the rawvideo codec tag.

[Michael Niedermayer]

On Tue, Jun 01, 2010 at 07:29:34PM +0200, Stefano Sabatini wrote:
> On date Tuesday 2010-06-01 17:53:36 +0200, Michael Niedermayer encoded:
> > On Tue, Jun 01, 2010 at 12:39:41PM +0200, Stefano Sabatini wrote:
> > > On date Thursday 2010-05-27 21:59:52 +0200, Michael Niedermayer encoded:
> > > > On Thu, May 27, 2010 at 12:28:28AM +0200, Stefano Sabatini wrote:
> > > > > Make the function fail if there is no codec tag associated to that
> > > > > pixel format.
> > > > > ---
> > > > >  libavformat/utils.c |    9 +++++++++
> > > > >  1 files changed, 9 insertions(+), 0 deletions(-)
> > > > 
> > > > this patch requires as prereqesite avienc/riff to override codec_tag
> > > > so its 0 for rgb formats
> > > 
> > > The problem with the current code is that if
> > > avcodec_pix_fmt_to_codec_tag(avctx->pix_fmt) in rawenc.c returns 0,
> > > then av_write_header() does:
> > > st->codec->codec_tag= av_codec_get_tag(s->oformat->codec_tag, st->codec->codec_id);
> > > 
> > > which sets the codec tag to the first entry with codec id == RAWVIDEO,
> > > which may have nothing to do with the pixel format of the output
> > > stream.
> > 
> > you are confused.
> > codec_tag must be 0 for rgb in avi. and the first entry is 0
> > if rgb in avi is stored with non 0 codec_tag currently then you
> > introduced a very serious bug. And the fix is to override it in
> > riff.c as i said multiple times.
> 
> I have not the faintest idea about what "rgb in avi" is, there are
> tons of RGB pixel formats which can fit in rawvideo, also I have no
> idea what you mean by "override it in riff.c" and I'm quite tired of
> playing at mind-guessing.

what is unclear on
rgb in avi must use codec_tag=0 ?
the raw rgb format in avi is indicated by the number of bits per pixel
not by the fourcc which must be set to 0.


> 
> What the code currently implements is just wrong for both AVI and NUT,
> in the case of AVI if the pixel format cannot be mapped to any codec
> tag, codec_tag is set to 0,

it must be 0 this is as it should be


> which when reading it is interpreted as
> YUV420P,

if so thats a bug and i would suspect a new one


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20100601/3969c5c3/attachment.pgp>