[FFmpeg-devel] [PATCH 2/3] cbs_av1: Support redundant frame headers

[Mark Thompson]

---
Includes support for using them when the normal frame header as been lost (try "-bsf:v filter_units=remove_types=3").


 libavcodec/cbs_av1.c                 |  8 +++-
 libavcodec/cbs_av1.h                 |  2 +
 libavcodec/cbs_av1_syntax_template.c | 64 +++++++++++++++++++++++++---
 3 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
index 1c49d90f51..b61b757f41 100644
--- a/libavcodec/cbs_av1.c
+++ b/libavcodec/cbs_av1.c
@@ -996,7 +996,9 @@ static int cbs_av1_read_unit(CodedBitstreamContext *ctx,
     case AV1_OBU_REDUNDANT_FRAME_HEADER:
         {
             err = cbs_av1_read_frame_header_obu(ctx, &gbc,
-                                                &obu->obu.frame_header);
+                                                &obu->obu.frame_header,
+                                                obu->header.obu_type ==
+                                                AV1_OBU_REDUNDANT_FRAME_HEADER);
             if (err < 0)
                 return err;
         }
@@ -1124,7 +1126,9 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
     case AV1_OBU_REDUNDANT_FRAME_HEADER:
         {
             err = cbs_av1_write_frame_header_obu(ctx, pbc,
-                                                 &obu->obu.frame_header);
+                                                 &obu->obu.frame_header,
+                                                 obu->header.obu_type ==
+                                                 AV1_OBU_REDUNDANT_FRAME_HEADER);
             if (err < 0)
                 return err;
         }
diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
index b66a09c389..af9e88df71 100644
--- a/libavcodec/cbs_av1.h
+++ b/libavcodec/cbs_av1.h
@@ -400,6 +400,8 @@ typedef struct CodedBitstreamAV1Context {
     AVBufferRef          *sequence_header_ref;
 
     int seen_frame_header;
+    uint8_t *frame_header;
+    size_t   frame_header_size;
 
     int temporal_id;
     int spatial_id;
diff --git a/libavcodec/cbs_av1_syntax_template.c b/libavcodec/cbs_av1_syntax_template.c
index e146bbf8bb..5649af841a 100644
--- a/libavcodec/cbs_av1_syntax_template.c
+++ b/libavcodec/cbs_av1_syntax_template.c
@@ -1463,24 +1463,76 @@ static int FUNC(uncompressed_header)(CodedBitstreamContext *ctx, RWContext *rw,
 }
 
 static int FUNC(frame_header_obu)(CodedBitstreamContext *ctx, RWContext *rw,
-                                  AV1RawFrameHeader *current)
+                                  AV1RawFrameHeader *current, int redundant)
 {
     CodedBitstreamAV1Context *priv = ctx->priv_data;
-    int err;
-
-    HEADER("Frame Header");
+    int start_pos, fh_bits, fh_bytes, err;
+    const uint8_t *fh_start;
 
     if (priv->seen_frame_header) {
-        // Nothing to do.
+        if (!redundant) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid repeated "
+                   "frame header OBU.\n");
+            return AVERROR_INVALIDDATA;
+        } else {
+            GetBitContext fh;
+            size_t k;
+            int b;
+
+            HEADER("Redundant Frame Header");
+
+            init_get_bits(&fh, priv->frame_header,
+                          priv->frame_header_size);
+            for (k = 0; k < priv->frame_header_size; k++) {
+                b = get_bits1(&fh);
+                xf(1, frame_header_copy[k], b, b, b, 1, k);
+            }
+        }
     } else {
+        if (redundant)
+            HEADER("Redundant Frame Header (used as Frame Header)");
+        else
+            HEADER("Frame Header");
+
         priv->seen_frame_header = 1;
 
+#ifdef READ
+        start_pos = get_bits_count(rw);
+#else
+        start_pos = put_bits_count(rw);
+#endif
+
         CHECK(FUNC(uncompressed_header)(ctx, rw, current));
 
         if (current->show_existing_frame) {
             priv->seen_frame_header = 0;
         } else {
             priv->seen_frame_header = 1;
+
+            av_freep(&priv->frame_header);
+
+#ifdef READ
+            fh_bits  = get_bits_count(rw) - start_pos;
+            fh_start = rw->buffer + start_pos / 8;
+#else
+            // Need to flush the bitwriter so that we can copy its output,
+            // but use a copy so we don't affect the caller's structure.
+            {
+                PutBitContext tmp = *rw;
+                flush_put_bits(&tmp);
+            }
+
+            fh_bits  = put_bits_count(rw) - start_pos;
+            fh_start = rw->buf + start_pos / 8;
+#endif
+            fh_bytes = (fh_bits + 7) / 8;
+
+            priv->frame_header_size = fh_bits;
+            priv->frame_header =
+                av_mallocz(fh_bytes + AV_INPUT_BUFFER_PADDING_SIZE);
+            if (!priv->frame_header)
+                return AVERROR(ENOMEM);
+            memcpy(priv->frame_header, fh_start, fh_bytes);
         }
     }
 
@@ -1528,7 +1580,7 @@ static int FUNC(frame_obu)(CodedBitstreamContext *ctx, RWContext *rw,
 {
     int err;
 
-    CHECK(FUNC(frame_header_obu)(ctx, rw, &current->header));
+    CHECK(FUNC(frame_header_obu)(ctx, rw, &current->header, 0));
 
     CHECK(FUNC(byte_alignment)(ctx, rw));
 
-- 
2.19.1