[FFmpeg-devel] [PATCH 2/8] av1_metadata: Add option to update video parameters

[Andreas Rheinhardt]

Up until now, this BSF only changed the bitstream, not the
AVCodecParameters. The result is that e.g. some muxers use outdated
information to write header information that conflicts with (and precedes)
the new information at the bitstream level, so that the updates might
not lead to the desired change.
This commit changes this. It adds a mechanism by which the new
information can be used to update the AVCodecParameters, too. This is
the new default and an option has been added to revert to the old
behaviour.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at googlemail.com>
---
 doc/bitstream_filters.texi    |  6 +++++
 libavcodec/av1_metadata_bsf.c | 43 +++++++++++++++++++++++++++++++----
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
index 15c578aa8a..80df345f26 100644
--- a/doc/bitstream_filters.texi
+++ b/doc/bitstream_filters.texi
@@ -87,6 +87,12 @@ the timing info in the sequence header.
 Set the number of ticks in each picture, to indicate that the stream
 has a fixed framerate.  Ignored if @option{tick_rate} is not also set.
 
+ at item full_update
+If this is set, the AVCodecParameters are updated in addition to the
+bitstream. If unset, muxers might add header information based upon the
+old AVCodecParameters that contradicts and potentially precedes the
+changes made at the bitstream level. On by default.
+
 @end table
 
 @section chomp
diff --git a/libavcodec/av1_metadata_bsf.c b/libavcodec/av1_metadata_bsf.c
index 52d383661f..0c8d00acea 100644
--- a/libavcodec/av1_metadata_bsf.c
+++ b/libavcodec/av1_metadata_bsf.c
@@ -46,11 +46,15 @@ typedef struct AV1MetadataContext {
 
     AVRational tick_rate;
     int num_ticks_per_picture;
+
+    int full_update;
 } AV1MetadataContext;
 
 
 static int av1_metadata_update_sequence_header(AVBSFContext *bsf,
-                                               AV1RawSequenceHeader *seq)
+                                               AV1RawSequenceHeader *seq,
+                                               int *color_range,
+                                               int *chroma_sample_position)
 {
     AV1MetadataContext *ctx = bsf->priv_data;
     AV1RawColorConfig  *clc = &seq->color_config;
@@ -82,6 +86,8 @@ static int av1_metadata_update_sequence_header(AVBSFContext *bsf,
                    "on RGB streams encoded in BT.709 sRGB.\n");
         } else {
             clc->color_range = ctx->color_range;
+            if (color_range)
+                *color_range = ctx->color_range;
         }
     }
 
@@ -91,6 +97,8 @@ static int av1_metadata_update_sequence_header(AVBSFContext *bsf,
                    "can only be set for 4:2:0 streams.\n");
         } else {
             clc->chroma_sample_position = ctx->chroma_sample_position;
+            if (chroma_sample_position)
+                *chroma_sample_position = ctx->chroma_sample_position;
         }
     }
 
@@ -135,7 +143,8 @@ static int av1_metadata_filter(AVBSFContext *bsf, AVPacket *out)
     for (i = 0; i < frag->nb_units; i++) {
         if (frag->units[i].type == AV1_OBU_SEQUENCE_HEADER) {
             obu = frag->units[i].content;
-            err = av1_metadata_update_sequence_header(bsf, &obu->obu.sequence_header);
+            err = av1_metadata_update_sequence_header(bsf, &obu->obu.sequence_header,
+                                                      NULL, NULL);
             if (err < 0)
                 goto fail;
         }
@@ -184,7 +193,7 @@ static int av1_metadata_init(AVBSFContext *bsf)
     AV1MetadataContext *ctx = bsf->priv_data;
     CodedBitstreamFragment *frag = &ctx->access_unit;
     AV1RawOBU *obu;
-    int err, i;
+    int err, i, color_range = -1, chroma_sample_position = -1;
 
     err = ff_cbs_init(&ctx->cbc, AV_CODEC_ID_AV1, bsf);
     if (err < 0)
@@ -200,7 +209,8 @@ static int av1_metadata_init(AVBSFContext *bsf)
         for (i = 0; i < frag->nb_units; i++) {
             if (frag->units[i].type == AV1_OBU_SEQUENCE_HEADER) {
                 obu = frag->units[i].content;
-                err = av1_metadata_update_sequence_header(bsf, &obu->obu.sequence_header);
+                err = av1_metadata_update_sequence_header(bsf, &obu->obu.sequence_header,
+                                                          &color_range, &chroma_sample_position);
                 if (err < 0)
                     goto fail;
             }
@@ -213,6 +223,28 @@ static int av1_metadata_init(AVBSFContext *bsf)
         }
     }
 
+    if (ctx->full_update) {
+        if (chroma_sample_position >= 0) {
+            const int conversion_table[4] = { AVCHROMA_LOC_UNSPECIFIED,
+                                              AVCHROMA_LOC_LEFT,
+                                              AVCHROMA_LOC_TOPLEFT,
+                                              AVCHROMA_LOC_UNSPECIFIED };
+            chroma_sample_position = conversion_table[chroma_sample_position];
+        }
+
+        if (ctx->color_range >= 0)
+            ctx->color_range++;
+
+        ff_cbs_update_video_parameters(ctx->cbc, bsf->par_out, -1, -1, -1, -1,
+                                       -1, color_range, ctx->color_primaries,
+                                       ctx->transfer_characteristics,
+                                       ctx->matrix_coefficients,
+                                       chroma_sample_position, -1);
+
+        if (ctx->color_range != -1)
+            ctx->color_range--;
+    }
+
     err = 0;
 fail:
     ff_cbs_fragment_uninit(ctx->cbc, frag);
@@ -273,6 +305,9 @@ static const AVOption av1_metadata_options[] = {
         OFFSET(num_ticks_per_picture), AV_OPT_TYPE_INT,
         { .i64 = -1 }, -1, INT_MAX, FLAGS },
 
+    { "full_update", "Update not only bitstream, but also AVCodecParameters.",
+        OFFSET(full_update), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, FLAGS},
+
     { NULL }
 };
 
-- 
2.19.1