If the video stream is H.264 with MP4 syntax, store the NAL lenght size in

the RTP muxer context (it will be used later for splitting frames in NALs)

Originally committed as revision 23625 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtpenc.c

@@ -131,6 +131,13 @@ static int rtp_write_header(AVFormatContext *s1)
         s->max_payload_size = n * TS_PACKET_SIZE;
         s->buf_ptr = s->buf;
         break;
+    case CODEC_ID_H264:
+        /* check for H.264 MP4 syntax */
+        if (st->codec->extradata_size > 0 && st->codec->extradata &&
+            st->codec->extradata[0] == 1) {
+            s->nal_length_size = (st->codec->extradata[4] & 0x03) + 1;
+        }
+        break;
     case CODEC_ID_AMR_NB:
     case CODEC_ID_AMR_WB:
         if (!s->max_frames_per_packet)

libavformat/rtpenc.h

@@ -50,6 +50,12 @@ struct RTPMuxContext {
     uint8_t *buf_ptr;
 
     int max_frames_per_packet;
+
+    /**
+     * Number of bytes used for H.264 NAL length, if the MP4 syntax is used
+     * (1, 2 or 4)
+     */
+    int nal_length_size;
 };
 
 typedef struct RTPMuxContext RTPMuxContext;