avcodec/av1_parse: take trailing bits into account when initializing the GetBitContext

Also only initialize it in ff_av1_packet_split() and not ff_av1_extract_obu(),
same as h2645_parse, so GetBitContext specific failures may not affect the
latter.

Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/libavcodec/av1_parse.h b/libavcodec/av1_parse.h
index 9a6e6835ab..0de619dbec 100644
--- a/libavcodec/av1_parse.h
+++ b/libavcodec/av1_parse.h
@@ -23,6 +23,7 @@
 
 #include <stdint.h>
 
+#include "av1.h"
 #include "avcodec.h"
 #include "get_bits.h"
 
@@ -31,6 +32,12 @@ typedef struct AV1OBU {
     int size;
     const uint8_t *data;
 
+    /**
+     * Size, in bits, of just the data, excluding the trailing_one_bit and
+     * any trailing padding.
+     */
+    int size_bits;
+
     /** Size of entire OBU, including header */
     int raw_size;
     const uint8_t *raw_data;
@@ -133,4 +140,35 @@ static inline int parse_obu_header(const uint8_t *buf, int buf_size,
     return size;
 }
 
+static inline int get_obu_bit_length(const uint8_t *buf, int size, int type)
+{
+    int v;
+
+    /* There are no trailing bits on these */
+    if (type == AV1_OBU_TILE_GROUP || type == AV1_OBU_FRAME) {
+        if (size > INT_MAX / 8)
+            return AVERROR(ERANGE);
+        else
+            return size * 8;
+    }
+
+    while (size > 0 && buf[size - 1] == 0)
+        size--;
+
+    if (!size)
+        return 0;
+
+    v = buf[size - 1];
+
+    if (size > INT_MAX / 8)
+        return AVERROR(ERANGE);
+    size *= 8;
+
+    /* Remove the trailing_one_bit and following trailing zeros */
+    if (v)
+        size -= ff_ctz(v) + 1;
+
+    return size;
+}
+
 #endif /* AVCODEC_AV1_PARSE_H */