[FFmpeg-devel] [PATCH v2] avfilter/vf_scale: translate and verify swscale internal range flag

[Michael Niedermayer]

On Sun, Sep 20, 2020 at 01:36:56PM +0300, Jan Ekström wrote:
> This value - while it looks like the actual range of the content -
> is nothing but the internal value of swscale.
> 
> Thus, if we have RGB content, translate the value to 1 which is what
> at least this filter expects for RGB. Swscale will ignore this value
> when set.
> 
> Additionally, after calling sws_setColorspaceDetails double-check
> the configured internal flag for the color range. Warn if this is
> different to the requested value.
> 
> Finally, utilize the translated configured output value as the
> output AVFrame's color_range.
> ---
>  libavfilter/vf_scale.c | 44 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
> index 58eee96744..da8ce399cf 100644
> --- a/libavfilter/vf_scale.c
> +++ b/libavfilter/vf_scale.c
> @@ -647,6 +647,8 @@ static int scale_slice(AVFilterLink *link, AVFrame *out_buf, AVFrame *cur_pic, s
>                           out,out_stride);
>  }
>  
> +// swscale's internal range flag is 0 for RGB, which we have to override
> +#define NORMALIZE_SWS_RANGE(format_flags, sws_range) (((format_flags) & AV_PIX_FMT_FLAG_RGB) ? 1 : (sws_range))
>  static int scale_frame(AVFilterLink *link, AVFrame *in, AVFrame **frame_out)
>  {
>      AVFilterContext *ctx = link->dst;
> @@ -750,11 +752,19 @@ scale:
>          || in_range != AVCOL_RANGE_UNSPECIFIED
>          || scale->out_range != AVCOL_RANGE_UNSPECIFIED) {
>          int in_full, out_full, brightness, contrast, saturation;
> +        int configured_in_full_range_flag, configured_out_full_range_flag;
>          const int *inv_table, *table;
> +        const AVPixFmtDescriptor *in_desc  = av_pix_fmt_desc_get(in->format);
> +        const AVPixFmtDescriptor *out_desc = av_pix_fmt_desc_get(out->format);
> +        av_assert0(in_desc && out_desc);
>  
>          sws_getColorspaceDetails(scale->sws, (int **)&inv_table, &in_full,
>                                   (int **)&table, &out_full,
>                                   &brightness, &contrast, &saturation);
> +        // translate the internal range flags according to this
> +        // filter's expectations for RGB.
> +        in_full = NORMALIZE_SWS_RANGE(in_desc->flags, in_full);
> +        out_full = NORMALIZE_SWS_RANGE(out_desc->flags, out_full);
>  
>          if (scale->in_color_matrix)
>              inv_table = parse_yuv_type(scale->in_color_matrix, in->colorspace);
> @@ -782,7 +792,39 @@ scale:
>                                       table, out_full,
>                                       brightness, contrast, saturation);
>  
> -        out->color_range = out_full ? AVCOL_RANGE_JPEG : AVCOL_RANGE_MPEG;
> +        // double-check what was actually just configured,
> +        // since swscale can silently ignore the color range
> +        // value in sws_setColorspaceDetails.
> +        sws_getColorspaceDetails(scale->sws, (int **)&inv_table,
> +                                 &configured_in_full_range_flag,
> +                                 (int **)&table,
> +                                 &configured_out_full_range_flag,
> +                                 &brightness, &contrast, &saturation);
> +
> +        // translate the actually configured internal range flags according
> +        // to this filter's expectations for RGB.
> +        configured_in_full_range_flag = \
> +            NORMALIZE_SWS_RANGE(in_desc->flags,
> +                                configured_in_full_range_flag);
> +        configured_out_full_range_flag = \
> +            NORMALIZE_SWS_RANGE(out_desc->flags,
> +                                configured_out_full_range_flag);
> +
> +        if (in_full != configured_in_full_range_flag ||
> +            out_full != configured_out_full_range_flag) {
> +            av_log(ctx, AV_LOG_WARNING,
> +                   "swscale overrode set input/output range value as it "
> +                   "considered it an invalid configuration! "
> +                   "(input: requested: %s, configured: %s), "
> +                   "(output: requested: %s, configured: %s)!\n",
> +                   in_full ? "full" : "limited",
> +                   configured_in_full_range_flag ? "full" : "limited",
> +                   out_full ? "full" : "limited",
> +                   configured_out_full_range_flag ? "full" : "limited");
> +        }

If i read this correctly, please correct me if i misread this
swscale is setup with some ranges and ignores it.
Is there a reason why swscale should not print a warning in this case ?
iam asking as you print this from one user of swscale.
wouldnt this be relevant to other users too ?


thx

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

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20200920/d60a7022/attachment.sig>