avcodec/mpeg4videodec: Fix nonsense warning

Since db772308 parsing of
mpeg4-extradata lead to a "Failed to parse extradata" warning, because
ff_mpeg4_decode_picture_header returns AVERROR_INVALIDDATA in case that
no VOP was found. This patch adds a parameter to signify whether a
header (where the absence of a VOP does not raise an error) or not is
parsed. The first mode is of course used for parsing headers.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@googlemail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/h263dec.c

@@ -500,9 +500,9 @@ retry:
             GetBitContext gb;
 
             if (init_get_bits8(&gb, s->avctx->extradata, s->avctx->extradata_size) >= 0 )
-                ff_mpeg4_decode_picture_header(avctx->priv_data, &gb);
+                ff_mpeg4_decode_picture_header(avctx->priv_data, &gb, 1);
         }
-        ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb);
+        ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb, 0);
     } else if (CONFIG_H263I_DECODER && s->codec_id == AV_CODEC_ID_H263I) {
         ret = ff_intel_h263_decode_picture_header(s);
     } else if (CONFIG_FLV_DECODER && s->h263_flv) {

libavcodec/mpeg4video.h

@@ -163,7 +163,7 @@ void ff_mpeg4_pred_ac(MpegEncContext *s, int16_t *block, int n,
 void ff_set_mpeg4_time(MpegEncContext *s);
 int ff_mpeg4_encode_picture_header(MpegEncContext *s, int picture_number);
 
-int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb);
+int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, int header);
 void ff_mpeg4_encode_video_packet_header(MpegEncContext *s);
 void ff_mpeg4_clean_buffers(MpegEncContext *s);
 void ff_mpeg4_stuffing(PutBitContext *pbc);

libavcodec/mpeg4video_parser.c

@@ -89,13 +89,13 @@ static int mpeg4_decode_header(AVCodecParserContext *s1, AVCodecContext *avctx,
 
     if (avctx->extradata_size && pc->first_picture) {
         init_get_bits(gb, avctx->extradata, avctx->extradata_size * 8);
-        ret = ff_mpeg4_decode_picture_header(dec_ctx, gb);
-        if (ret < -1)
+        ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 1);
+        if (ret < 0)
             av_log(avctx, AV_LOG_WARNING, "Failed to parse extradata\n");
     }
 
     init_get_bits(gb, buf, 8 * buf_size);
-    ret = ff_mpeg4_decode_picture_header(dec_ctx, gb);
+    ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 0);
     if (s->width && (!avctx->width || !avctx->height ||
                      !avctx->coded_width || !avctx->coded_height)) {
         ret = ff_set_dimensions(avctx, s->width, s->height);

libavcodec/mpeg4videodec.c

@@ -3203,11 +3203,13 @@ static int decode_studio_vol_header(Mpeg4DecContext *ctx, GetBitContext *gb)
 
 /**
  * Decode MPEG-4 headers.
- * @return <0 if no VOP found (or a damaged one)
+ *
+ * @param  header If set the absence of a VOP is not treated as error; otherwise, it is treated as such.
+ * @return <0 if an error occured
  *         FRAME_SKIPPED if a not coded VOP is found
- *         0 if a VOP is found
+ *         0 else
  */
-int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb)
+int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, int header)
 {
     MpegEncContext *s = &ctx->m;
     unsigned startcode, v;
@@ -3236,6 +3238,8 @@ int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb)
                 (ctx->divx_version >= 0 || ctx->xvid_build >= 0) || s->codec_tag == AV_RL32("QMP4")) {
                 av_log(s->avctx, AV_LOG_VERBOSE, "frame skip %d\n", gb->size_in_bits);
                 return FRAME_SKIPPED;  // divx bug
+            } else if (header && get_bits_count(gb) == gb->size_in_bits) {
+                return 0; // ordinary return value for parsing of extradata
             } else
                 return AVERROR_INVALIDDATA;  // end of stream
         }