Re: [FFmpeg-devel] [PATCH v2] avfilter: propagate colorspace and color_range from buffer filter and between AVFilterLink.

[Niklas Haas <ffmpeg@haasn.xyz>]

On Sun, 24 Mar 2024 10:26:35 +0100 Damiano Galassi <damiog@gmail.com> wrote:
> There two new fields were never sent down the filter chain,
> and no filter after the first had colorspace and color_range set,
> causing breakage in zscale and possible other filters.
> ---
>  libavfilter/avfilter.c  | 4 ++++
>  libavfilter/buffersrc.c | 2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
> index 831871de90..66733f5ecf 100644
> --- a/libavfilter/avfilter.c
> +++ b/libavfilter/avfilter.c
> @@ -391,6 +391,10 @@ int ff_filter_config_links(AVFilterContext *filter)
>                          link->w = inlink->w;
>                      if (!link->h)
>                          link->h = inlink->h;
> +                    if (link->colorspace == AVCOL_SPC_UNSPECIFIED)
> +                        link->colorspace = inlink->colorspace;
> +                    if (link->color_range == AVCOL_RANGE_UNSPECIFIED)
> +                        link->color_range = inlink->color_range;
>                  } else if (!link->w || !link->h) {
>                      av_log(link->src, AV_LOG_ERROR,
>                             "Video source filters must set their output link's "
> diff --git a/libavfilter/buffersrc.c b/libavfilter/buffersrc.c
> index ddcd403785..2760097edf 100644
> --- a/libavfilter/buffersrc.c
> +++ b/libavfilter/buffersrc.c
> @@ -499,6 +499,8 @@ static int config_props(AVFilterLink *link)
>          link->w = c->w;
>          link->h = c->h;
>          link->sample_aspect_ratio = c->pixel_aspect;
> +        link->colorspace = c->color_space;
> +        link->color_range = c->color_range;
>  
>          if (c->hw_frames_ctx) {
>              link->hw_frames_ctx = av_buffer_ref(c->hw_frames_ctx);

This still breaks FATE.

I think the problem is that AVCOL_SPC_UNSPECIFIED is a valid,
configurable possibility for this field. So we need to set it to -1
initially to distinguish "not set" from "unspecified".

This diff resolves the FATE breakage:

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 153fb700d30..2f22c9143df 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -186,7 +186,8 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
     link->type    = src->output_pads[srcpad].type;
     av_assert0(AV_PIX_FMT_NONE == -1 && AV_SAMPLE_FMT_NONE == -1);
     link->format  = -1;
-    link->colorspace = AVCOL_SPC_UNSPECIFIED;
+    link->colorspace = AVCOL_SPC_NONE;
+    link->color_range = AVCOL_RANGE_NONE;
     ff_framequeue_init(&li->fifo, &fffiltergraph(src->graph)->frame_queues);
 
     return 0;
@@ -391,9 +392,9 @@ int ff_filter_config_links(AVFilterContext *filter)
                         link->w = inlink->w;
                     if (!link->h)
                         link->h = inlink->h;
-                    if (link->colorspace == AVCOL_SPC_UNSPECIFIED)
+                    if (link->colorspace < 0)
                         link->colorspace = inlink->color_range;
-                    if (link->color_range == AVCOL_RANGE_UNSPECIFIED)
+                    if (link->color_range < 0)
                         link->color_range = inlink->color_range;
                 } else if (!link->w || !link->h) {
                     av_log(link->src, AV_LOG_ERROR,
diff --git a/libavutil/pixfmt.h b/libavutil/pixfmt.h
index 4aa20e4e585..605881a43de 100644
--- a/libavutil/pixfmt.h
+++ b/libavutil/pixfmt.h
@@ -607,6 +607,7 @@ enum AVColorTransferCharacteristic {
  * These values match the ones defined by ISO/IEC 23091-2_2019 subclause 8.3.
  */
 enum AVColorSpace {
+    AVCOL_SPC_NONE        = -1, ///< invalid (reserved for internal use)
     AVCOL_SPC_RGB         = 0,  ///< order of coefficients is actually GBR, also IEC 61966-2-1 (sRGB), YZX and ST 428-1
     AVCOL_SPC_BT709       = 1,  ///< also ITU-R BT1361 / IEC 61966-2-4 xvYCC709 / derived in SMPTE RP 177 Annex B
     AVCOL_SPC_UNSPECIFIED = 2,
@@ -646,6 +647,7 @@ enum AVColorSpace {
  *     bit unsigned integer range, please refer to BT.2100 (Table 9).
  */
 enum AVColorRange {
+    AVCOL_RANGE_NONE = -1, ///< invalid (reserved for internal use)
     AVCOL_RANGE_UNSPECIFIED = 0,
 
     /**
diff --git a/tests/ref/fate/rgb24-mkv b/tests/ref/fate/rgb24-mkv
index 1cbed136dde..99234f10523 100644
--- a/tests/ref/fate/rgb24-mkv
+++ b/tests/ref/fate/rgb24-mkv
@@ -1,5 +1,5 @@
-7d767e8238c674ecfa80458cb281c09e *tests/data/fate/rgb24-mkv.matroska
-58236 tests/data/fate/rgb24-mkv.matroska
+e181dc84058c3584598333dabd110123 *tests/data/fate/rgb24-mkv.matroska
+58225 tests/data/fate/rgb24-mkv.matroska
 #tb 0: 1/10
 #media_type 0: video
 #codec_id 0: rawvideo
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