Re: [FFmpeg-devel] [PATCH v3 2/2] avfilter/vf_colorspace: Use colorspace negotiation API

[Niklas Haas <ffmpeg@haasn.xyz>]

On Tue, 02 Apr 2024 15:05:59 +0200 Nicolas Gaullier <nicolas.gaullier@cji.paris> wrote:
> Fixes a regression due to the fact that the colorspace filter does
> not use the new API introduced by 8c7934f73ab6c568acaa.
> The scale filter uses it since 45e09a30419cc2a7251e, and the setparams
> filter since 3bf80df3ccd32aed23f0.
> 
> Example 1 - color_range specified:
> ffmpeg -f lavfi -i yuvtestsrc -vf setparams=color_primaries=bt470bg:
> color_trc=smpte170m:colorspace=bt470bg,colorspace=bt709:range=tv,scale
> ,showinfo -f null -frames 1 -
> 
> Before:
>   color_range:unknown color_space:bt470bg ...
> After:
>   color_range:tv color_space:bt709 ...
> 
> Example 2 - color_range pass-through:
> ffmpeg -f lavfi -i yuvtestsrc -vf "setparams=color_primaries=bt470bg:
> color_trc=smpte170m:colorspace=bt470bg:range=unknown,
> setparams=range=pc:enable='between(n,1,2)',
> setparams=range=tv:enable='between(n,2,3)',
> colorspace=bt709,scale,showinfo"
> -f null -frames 3 - 2>&1|awk "/color_/ {print \$4 \" \" \$5}"
> 
> Before:
> color_range:tv color_space:bt470bg
> color_range:tv color_space:bt470bg
> color_range:tv color_space:bt470bg
> After:
> color_range:unknown color_space:bt709
> color_range:pc color_space:bt709
> color_range:tv color_space:bt709
> 
> Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
> ---
>  libavfilter/vf_colorspace.c | 63 +++++++++++++++++++++----------------
>  1 file changed, 36 insertions(+), 27 deletions(-)
> 
> diff --git a/libavfilter/vf_colorspace.c b/libavfilter/vf_colorspace.c
> index d181e81ace..12a571172b 100644
> --- a/libavfilter/vf_colorspace.c
> +++ b/libavfilter/vf_colorspace.c
> @@ -433,8 +433,7 @@ static int create_filtergraph(AVFilterContext *ctx,
>      if (out->color_trc       != s->out_trc) s->out_txchr     = NULL;
>      if (in->colorspace       != s->in_csp ||
>          in->color_range      != s->in_rng)  s->in_lumacoef   = NULL;
> -    if (out->colorspace      != s->out_csp ||
> -        out->color_range     != s->out_rng) s->out_lumacoef  = NULL;
> +    if (out->color_range     != s->out_rng) s->rgb2yuv       = NULL;

Can you explain this change to me?

>  
>      if (!s->out_primaries || !s->in_primaries) {
>          s->in_prm = in->color_primaries;
> @@ -563,26 +562,8 @@ static int create_filtergraph(AVFilterContext *ctx,
>          redo_yuv2rgb = 1;
>      }
>  
> -    if (!s->out_lumacoef) {
> -        s->out_csp = out->colorspace;
> +    if (!s->rgb2yuv) {
>          s->out_rng = out->color_range;
> -        s->out_lumacoef = av_csp_luma_coeffs_from_avcsp(s->out_csp);
> -        if (!s->out_lumacoef) {
> -            if (s->out_csp == AVCOL_SPC_UNSPECIFIED) {
> -                if (s->user_all == CS_UNSPECIFIED) {
> -                    av_log(ctx, AV_LOG_ERROR,
> -                           "Please specify output colorspace\n");
> -                } else {
> -                    av_log(ctx, AV_LOG_ERROR,
> -                           "Unsupported output color property %d\n", s->user_all);
> -                }
> -            } else {
> -                av_log(ctx, AV_LOG_ERROR,
> -                       "Unsupported output colorspace %d (%s)\n", s->out_csp,
> -                       av_color_space_name(s->out_csp));
> -            }
> -            return AVERROR(EINVAL);
> -        }
>          redo_rgb2yuv = 1;
>      }
>  
> @@ -687,6 +668,26 @@ static av_cold int init(AVFilterContext *ctx)
>  {
>      ColorSpaceContext *s = ctx->priv;
>  
> +    s->out_csp  = s->user_csp == AVCOL_SPC_UNSPECIFIED ?
> +                  default_csp[FFMIN(s->user_all, CS_NB)] : s->user_csp;
> +    s->out_lumacoef = av_csp_luma_coeffs_from_avcsp(s->out_csp);
> +    if (!s->out_lumacoef) {
> +        if (s->out_csp == AVCOL_SPC_UNSPECIFIED) {
> +            if (s->user_all == CS_UNSPECIFIED) {
> +                av_log(ctx, AV_LOG_ERROR,
> +                       "Please specify output colorspace\n");
> +            } else {
> +                av_log(ctx, AV_LOG_ERROR,
> +                       "Unsupported output color property %d\n", s->user_all);
> +            }
> +        } else {
> +            av_log(ctx, AV_LOG_ERROR,
> +                   "Unsupported output colorspace %d (%s)\n", s->out_csp,
> +                   av_color_space_name(s->out_csp));
> +        }
> +        return AVERROR(EINVAL);
> +    }
> +
>      ff_colorspacedsp_init(&s->dsp);
>  
>      return 0;
> @@ -735,6 +736,9 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
>          return res;
>      }
>  
> +    out->colorspace = s->out_csp;
> +    outlink->color_range = s->user_rng != AVCOL_RANGE_UNSPECIFIED ? s->user_rng : in->color_range;
> +    out->color_range = outlink->color_range;

Changing outlink dynamically like this seems not correct to me (what if
the next filter in the chain only supports one color range?). Changing
the range on the fly would at the minimum require reconfiguring the
filter graph, and possibly insertion of more auto-scale filters.

The logic that is used in the other YUV negotiation aware filters is to
just set `out->colorspace = outlink->colorspace` and `out->color_range
= outlink->color_range`, since the link properties are authoritative.

>      out->color_primaries = s->user_prm == AVCOL_PRI_UNSPECIFIED ?
>                             default_prm[FFMIN(s->user_all, CS_NB)] : s->user_prm;
>      if (s->user_trc == AVCOL_TRC_UNSPECIFIED) {
> @@ -746,10 +750,6 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
>      } else {
>          out->color_trc   = s->user_trc;
>      }
> -    out->colorspace      = s->user_csp == AVCOL_SPC_UNSPECIFIED ?
> -                           default_csp[FFMIN(s->user_all, CS_NB)] : s->user_csp;
> -    out->color_range     = s->user_rng == AVCOL_RANGE_UNSPECIFIED ?
> -                           in->color_range : s->user_rng;
>      if (rgb_sz != s->rgb_sz) {
>          const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(out->format);
>          int uvw = in->width >> desc->log2_chroma_w;
> @@ -839,10 +839,19 @@ static int query_formats(AVFilterContext *ctx)
>          AV_PIX_FMT_YUVJ420P,  AV_PIX_FMT_YUVJ422P,  AV_PIX_FMT_YUVJ444P,
>          AV_PIX_FMT_NONE
>      };
> -    int res;
> +    int res, ret;

Nit: Why introduce a new result variable instead of re-using the one
that's already declared?

>      ColorSpaceContext *s = ctx->priv;
> +    AVFilterLink *outlink = ctx->outputs[0];
>      AVFilterFormats *formats = ff_make_format_list(pix_fmts);
>  
> +    if (ret = ff_formats_ref(ff_make_formats_list_singleton(s->out_csp),
> +                             &outlink->incfg.color_spaces) < 0)
> +        return ret;
> +    if (s->user_rng != AVCOL_RANGE_UNSPECIFIED
> +        && (ret = ff_formats_ref(ff_make_formats_list_singleton(s->user_rng),
> +                             &outlink->incfg.color_ranges) < 0))
> +        return ret;
> +

IMO this logic would look cleaner if you assigned ret before testing it,
especially since it's nested.

>      if (!formats)
>          return AVERROR(ENOMEM);
>      if (s->user_format == AV_PIX_FMT_NONE)
> @@ -855,7 +864,7 @@ static int query_formats(AVFilterContext *ctx)
>      if (res < 0)
>          return res;
>  
> -    return ff_formats_ref(formats, &ctx->outputs[0]->incfg.formats);
> +    return ff_formats_ref(formats, &outlink->incfg.formats);
>  }
>  
>  static int config_props(AVFilterLink *outlink)
> -- 
> 2.30.2
> 
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