avcodec/cbs_av1: add support for Padding OBUs

Based on itut_t35 Matadata OBU parsing code.
Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/cbs_av1.c

@@ -868,6 +868,11 @@ static void cbs_av1_free_tile_data(AV1RawTileData *td)
     av_buffer_unref(&td->data_ref);
 }
 
+static void cbs_av1_free_padding(AV1RawPadding *pd)
+{
+    av_buffer_unref(&pd->payload_ref);
+}
+
 static void cbs_av1_free_metadata(AV1RawMetadata *md)
 {
     switch (md->metadata_type) {
@@ -894,6 +899,9 @@ static void cbs_av1_free_obu(void *unit, uint8_t *content)
     case AV1_OBU_METADATA:
         cbs_av1_free_metadata(&obu->obu.metadata);
         break;
+    case AV1_OBU_PADDING:
+        cbs_av1_free_padding(&obu->obu.padding);
+        break;
     }
 
     av_freep(&obu);
@@ -1068,6 +1076,12 @@ static int cbs_av1_read_unit(CodedBitstreamContext *ctx,
         }
         break;
     case AV1_OBU_PADDING:
+        {
+            err = cbs_av1_read_padding_obu(ctx, &gbc, &obu->obu.padding);
+            if (err < 0)
+                return err;
+        }
+        break;
     default:
         return AVERROR(ENOSYS);
     }
@@ -1193,6 +1207,12 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
         }
         break;
     case AV1_OBU_PADDING:
+        {
+            err = cbs_av1_write_padding_obu(ctx, pbc, &obu->obu.padding);
+            if (err < 0)
+                return err;
+        }
+        break;
     default:
         return AVERROR(ENOSYS);
     }

libavcodec/cbs_av1.h

@@ -364,6 +364,12 @@ typedef struct AV1RawMetadata {
     } metadata;
 } AV1RawMetadata;
 
+typedef struct AV1RawPadding {
+    uint8_t     *payload;
+    size_t       payload_size;
+    AVBufferRef *payload_ref;
+} AV1RawPadding;
+
 
 typedef struct AV1RawOBU {
     AV1RawOBUHeader header;
@@ -377,6 +383,7 @@ typedef struct AV1RawOBU {
         AV1RawTileGroup      tile_group;
         AV1RawTileList       tile_list;
         AV1RawMetadata       metadata;
+        AV1RawPadding        padding;
     } obu;
 } AV1RawOBU;
 

libavcodec/cbs_av1_syntax_template.c

@@ -1755,3 +1755,27 @@ static int FUNC(metadata_obu)(CodedBitstreamContext *ctx, RWContext *rw,
 
     return 0;
 }
+
+static int FUNC(padding_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                             AV1RawPadding *current)
+{
+    int i, err;
+
+    HEADER("Padding");
+
+#ifdef READ
+    // The payload runs up to the start of the trailing bits, but there might
+    // be arbitrarily many trailing zeroes so we need to read through twice.
+    current->payload_size = cbs_av1_get_payload_bytes_left(rw);
+
+    current->payload_ref = av_buffer_alloc(current->payload_size);
+    if (!current->payload_ref)
+        return AVERROR(ENOMEM);
+    current->payload = current->payload_ref->data;
+#endif
+
+    for (i = 0; i < current->payload_size; i++)
+        xf(8, obu_padding_byte[i], current->payload[i], 0x00, 0xff, 1, i);
+
+    return 0;
+}