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

[Stefano Sabatini]

On date Tuesday 2010-06-01 19:59:55 +0200, Michael Niedermayer encoded:
> 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

Not a new bug, I'm simply using FFmpeg in a way that nobody never did
(read: weird formats).

static av_cold int raw_init_decoder(AVCodecContext *avctx)
{
    RawVideoContext *context = avctx->priv_data;

    if (avctx->codec_tag == MKTAG('r','a','w',' '))
        avctx->pix_fmt = find_pix_fmt(pix_fmt_bps_mov, avctx->bits_per_coded_sample);
    else if (avctx->codec_tag)
        avctx->pix_fmt = find_pix_fmt(ff_raw_pix_fmt_tags, avctx->codec_tag);
    else if (avctx->bits_per_coded_sample)
        avctx->pix_fmt = find_pix_fmt(pix_fmt_bps_avi, avctx->bits_per_coded_sample);

find_pix_fmt() returns PIX_FMT_YUV420P when pix_fmt_bps_avi doesn't
contain an entry corresponding to avctx->bits_per_coded_sample, I'm
testing with bgr444 and there are no entry corresponding to bps = 12.

Regards.
-- 
FFmpeg = Funny and Free Magic Philosofic Extroverse God