[FFmpeg-devel] [PATCH 3/4] avcodec/cbs_av1: add an option to select an operating point

[James Almer]

This implements the function drop_obu() as defined in Setion 6.2.1 from the
spec.
In a reading only scenario, units that belong to an operating point the
caller doesn't want should not be parsed.

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavcodec/cbs_av1.c                 | 18 +++++++++++++++++-
 libavcodec/cbs_av1.h                 |  5 +++++
 libavcodec/cbs_av1_syntax_template.c |  7 +++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
index dcf6c140ae..edacc29ca8 100644
--- a/libavcodec/cbs_av1.c
+++ b/libavcodec/cbs_av1.c
@@ -18,6 +18,7 @@
 
 #include "libavutil/avassert.h"
 #include "libavutil/pixfmt.h"
+#include "libavutil/opt.h"
 
 #include "cbs.h"
 #include "cbs_internal.h"
@@ -883,7 +884,7 @@ static int cbs_av1_read_unit(CodedBitstreamContext *ctx,
             int in_spatial_layer  =
                 (priv->operating_point_idc >> (priv->spatial_id + 8)) & 1;
             if (!in_temporal_layer || !in_spatial_layer) {
-                // Decoding will drop this OBU at this operating point.
+                return AVERROR(EAGAIN); // drop_obu()
             }
         }
     }
@@ -1238,10 +1239,25 @@ static const CodedBitstreamUnitTypeDescriptor cbs_av1_unit_types[] = {
     CBS_UNIT_TYPE_END_OF_LIST
 };
 
+#define OFFSET(x) offsetof(CodedBitstreamAV1Context, x)
+static const AVOption cbs_av1_options[] = {
+    { "oppoint",  "Select an operating point of the scalable bitstream", OFFSET(operating_point),
+                  AV_OPT_TYPE_INT, { .i64 = -1 }, -1, AV1_MAX_OPERATING_POINTS - 1, 0 },
+    { NULL }
+};
+
+static const AVClass cbs_av1_class = {
+    .class_name = "cbs_av1",
+    .item_name  = av_default_item_name,
+    .option     = cbs_av1_options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 const CodedBitstreamType ff_cbs_type_av1 = {
     .codec_id          = AV_CODEC_ID_AV1,
 
     .priv_data_size    = sizeof(CodedBitstreamAV1Context),
+    .priv_class        = &cbs_av1_class,
 
     .unit_types        = cbs_av1_unit_types,
 
diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
index 7a0c08c596..27b44d68ff 100644
--- a/libavcodec/cbs_av1.h
+++ b/libavcodec/cbs_av1.h
@@ -416,6 +416,8 @@ typedef struct AV1ReferenceFrameState {
 } AV1ReferenceFrameState;
 
 typedef struct CodedBitstreamAV1Context {
+    const AVClass *class;
+
     AV1RawSequenceHeader *sequence_header;
     AVBufferRef          *sequence_header_ref;
 
@@ -443,6 +445,9 @@ typedef struct CodedBitstreamAV1Context {
     int tile_rows;
 
     AV1ReferenceFrameState ref[AV1_NUM_REF_FRAMES];
+
+    // AVOptions
+    int operating_point;
 } CodedBitstreamAV1Context;
 
 
diff --git a/libavcodec/cbs_av1_syntax_template.c b/libavcodec/cbs_av1_syntax_template.c
index bcaa334134..34d09fab68 100644
--- a/libavcodec/cbs_av1_syntax_template.c
+++ b/libavcodec/cbs_av1_syntax_template.c
@@ -186,6 +186,7 @@ static int FUNC(decoder_model_info)(CodedBitstreamContext *ctx, RWContext *rw,
 static int FUNC(sequence_header_obu)(CodedBitstreamContext *ctx, RWContext *rw,
                                      AV1RawSequenceHeader *current)
 {
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
     int i, err;
 
     HEADER("Sequence Header");
@@ -253,6 +254,12 @@ static int FUNC(sequence_header_obu)(CodedBitstreamContext *ctx, RWContext *rw,
             }
         }
     }
+    if (priv->operating_point >= 0) {
+        int op_pt = 0;
+        if (priv->operating_point <= current->operating_points_cnt_minus_1)
+            op_pt = priv->operating_point;
+        priv->operating_point_idc = current->operating_point_idc[op_pt];
+    }
 
     fb(4, frame_width_bits_minus_1);
     fb(4, frame_height_bits_minus_1);
-- 
2.27.0