avcodec/mpeg4video_parser: Fix incorrect spliting of MPEG-4 studio frames

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mpeg4video_parser.c

@@ -61,6 +61,8 @@ int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
         for (; i < buf_size; i++) {
             state = (state << 8) | buf[i];
             if ((state & 0xFFFFFF00) == 0x100) {
+                if (state == SLICE_STARTCODE || state == EXT_STARTCODE)
+                    continue;
                 pc->frame_start_found = 0;
                 pc->state             = -1;
                 return i - 3;