demux: expose demuxer colorimetry metadata to player

Implementation-wise, the values from the demuxer/codec header are merged
with the values from the decoder such that the former are used only
where the latter are unknown (0/auto).

demux/demux_mkv.c

@@ -1436,6 +1436,7 @@ static int demux_mkv_open_video(demuxer_t *demuxer, mkv_track_t *track)
     sh_v->par_h = p.p_h;
 
     sh_v->stereo_mode = track->stereo_mode;
+    sh_v->color = track->color;
 
 done:
     demux_add_sh_stream(demuxer, sh);

demux/stheader.h

@@ -22,6 +22,7 @@
 
 #include "common/common.h"
 #include "audio/chmap.h"
+#include "video/csputils.h"
 
 struct MPOpts;
 struct demuxer;
@@ -93,6 +94,7 @@ struct mp_codec_params {
     int disp_w, disp_h;   // display size
     int rotate;           // intended display rotation, in degrees, [0, 359]
     int stereo_mode;      // mp_stereo3d_mode (0 if none/unknown)
+    struct mp_colorspace color; // colorspace info where available
 
     // STREAM_VIDEO + STREAM_AUDIO
     int bits_per_coded_sample;

video/csputils.c

@@ -100,6 +100,22 @@ const struct m_opt_choice_alternatives mp_chroma_names[] = {
     {0}
 };
 
+void mp_colorspace_merge(struct mp_colorspace *orig, struct mp_colorspace *new)
+{
+    if (!orig->space)
+        orig->space = new->space;
+    if (!orig->levels)
+        orig->levels = new->levels;
+    if (!orig->primaries)
+        orig->primaries = new->primaries;
+    if (!orig->gamma)
+        orig->gamma = new->gamma;
+    if (!orig->nom_peak)
+        orig->nom_peak = new->nom_peak;
+    if (!orig->sig_peak)
+        orig->sig_peak = new->sig_peak;
+}
+
 // The short name _must_ match with what vf_stereo3d accepts (if supported).
 // The long name in comments is closer to the Matroska spec (StereoMode element).
 // The numeric index matches the Matroska StereoMode value. If you add entries

video/csputils.h

@@ -125,6 +125,9 @@ struct mp_colorspace {
     float sig_peak; // signal peak, highest value that occurs in the source
 };
 
+// Replaces unknown values in the first struct by those of the second struct
+void mp_colorspace_merge(struct mp_colorspace *orig, struct mp_colorspace *new);
+
 struct mp_csp_params {
     struct mp_colorspace color; // input colorspace
     enum mp_csp_levels levels_out; // output device

video/decode/dec_video.c

@@ -245,6 +245,7 @@ static void fix_image_params(struct dec_video *d_video,
     p.stereo_out = opts->video_stereo_mode;
 
     // Detect colorspace from resolution.
+    mp_colorspace_merge(&p.color, &c->color);
     mp_image_params_guess_csp(&p);
 
     d_video->last_format = *params;