[FFmpeg-devel] [PATCH]Force tv range for mpeg4 gray output

[wm4]

On Sat, 9 May 2015 12:30:32 +0200
Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> On Saturday 09 May 2015 11:53:13 am wm4 wrote:
> > On Sat, 9 May 2015 11:12:46 +0200
> >
> > Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> > > diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
> > > index c47f5b1..162c295 100644
> > > --- a/libavcodec/h263dec.c
> > > +++ b/libavcodec/h263dec.c
> > > @@ -48,8 +48,10 @@ static enum AVPixelFormat
> > > h263_get_format(AVCodecContext *avctx) if (avctx->codec->id ==
> > > AV_CODEC_ID_MSS2)
> > >          return AV_PIX_FMT_YUV420P;
> > >
> > > -    if (CONFIG_GRAY && (avctx->flags & CODEC_FLAG_GRAY))
> > > +    if (CONFIG_GRAY && (avctx->flags & CODEC_FLAG_GRAY)) {
> > > +        avctx->color_range = AVCOL_RANGE_MPEG;
> > >          return AV_PIX_FMT_GRAY8;
> > > +    }
> > >
> > >      return avctx->pix_fmt = ff_get_format(avctx,
> > > avctx->codec->pix_fmts); }
> >
> > Are you sure this doesn't overwrite color_range values read from the
> > file? (I didn't check, but please make sure.)
> 
> asp and friends do not set the colour range but the user could, 
> new patch attached, thank you!
> 
> > It appears to me that making GRAY full range by default wasn't such a
> > good idea.
> 
> I tend to disagree.
> 
> > Also, this patch is libswscale specific
> 
> Isn't that what I said when we discussed the commit message of 
> your patch and you disagreed?
> 
> > - unless you document somewhere that GRAY is in fact not just 
> > like the Y plane of normal YUV formats, but is full range by default.
> 
> This wouldn't be correct: pix_fmt gray can be both full range 
> or mpeg range, I just believe that if nothing is set, libswscale 
> should assume full range (it has to assume something).
> So far you have neither given an example of a "codec" for which 
> this is different (I have, but I hope you agree these are very 
> uncommon usecases) nor an example of a usecase for which FFmpeg 
> can know the range and it should not be full range.
> 
> > The API is inconsistent and undocumented in this aspect.
> 
> Feel free to let libswscale print a warning if no scale was set.
> 
> Carl Eugen

As I said several times before, libswscale is an independent library,
and the API user doesn't necessarily use it.

So what does libswscale have to do with libavcodec? Nothing.