bethsoftvid: synchronize video timestamps with audio sample rate

According to unofficial documentation, the video rate is locked to the audio
sample rate. This results in proper synchronization of audio and video
timestamps from the demuxer. This only works if the first audio packet occurs
before the first video packet or the audio sample rate is the default rate of
11111 Hz, both of which are true for all samples in our archive.

libavformat/bethsoftvid.c

@@ -40,6 +40,8 @@ typedef struct BVID_DemuxContext
 {
     int nframes;
     int sample_rate;        /**< audio sample rate */
+    int width;              /**< video width       */
+    int height;             /**< video height      */
     /** delay value between frames, added to individual frame delay.
      * custom units, which will be added to other custom units (~=16ms according
      * to free, unofficial documentation) */
@@ -65,7 +67,6 @@ static int vid_read_header(AVFormatContext *s)
 {
     BVID_DemuxContext *vid = s->priv_data;
     AVIOContext *pb = s->pb;
-    AVStream *stream;
 
     /* load main header. Contents:
     *    bytes: 'V' 'I' 'D'
@@ -73,23 +74,15 @@ static int vid_read_header(AVFormatContext *s)
     */
     avio_skip(pb, 5);
     vid->nframes = avio_rl16(pb);
-
-    stream = avformat_new_stream(s, NULL);
-    if (!stream)
-        return AVERROR(ENOMEM);
-    vid->video_index = stream->index;
-    stream->start_time = 0;
-    avpriv_set_pts_info(stream, 32, 1, 60);     // 16 ms increments, i.e. 60 fps
-    stream->codec->codec_type = AVMEDIA_TYPE_VIDEO;
-    stream->codec->codec_id = CODEC_ID_BETHSOFTVID;
-    stream->codec->width = avio_rl16(pb);
-    stream->codec->height = avio_rl16(pb);
-    stream->codec->pix_fmt = PIX_FMT_PAL8;
+    vid->width   = avio_rl16(pb);
+    vid->height  = avio_rl16(pb);
     vid->bethsoft_global_delay = avio_rl16(pb);
     avio_rl16(pb);
 
-    // wait until the first audio packet to create the audio stream
+    // wait until the first packet to create each stream
+    vid->video_index = -1;
     vid->audio_index = -1;
+    vid->sample_rate = DEFAULT_SAMPLE_RATE;
     s->ctx_flags |= AVFMTCTX_NOHEADER;
 
     return 0;
@@ -97,15 +90,34 @@ static int vid_read_header(AVFormatContext *s)
 
 #define BUFFER_PADDING_SIZE 1000
 static int read_frame(BVID_DemuxContext *vid, AVIOContext *pb, AVPacket *pkt,
-                      uint8_t block_type, AVFormatContext *s, int npixels)
+                      uint8_t block_type, AVFormatContext *s)
 {
     uint8_t * vidbuf_start = NULL;
     int vidbuf_nbytes = 0;
     int code;
     int bytes_copied = 0;
-    int position, duration;
+    int position, duration, npixels;
     unsigned int vidbuf_capacity;
     int ret = 0;
+    AVStream *st;
+
+    if (vid->video_index < 0) {
+        st = avformat_new_stream(s, NULL);
+        if (!st)
+            return AVERROR(ENOMEM);
+        vid->video_index = st->index;
+        if (vid->audio_index < 0) {
+            av_log_ask_for_sample(s, "No audio packet before first video "
+                                  "packet. Using default video time base.\n");
+        }
+        avpriv_set_pts_info(st, 64, 185, vid->sample_rate);
+        st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
+        st->codec->codec_id   = CODEC_ID_BETHSOFTVID;
+        st->codec->width      = vid->width;
+        st->codec->height     = vid->height;
+    }
+    st      = s->streams[vid->video_index];
+    npixels = st->codec->width * st->codec->height;
 
     vidbuf_start = av_malloc(vidbuf_capacity = BUFFER_PADDING_SIZE);
     if(!vidbuf_start)
@@ -248,8 +260,7 @@ static int vid_read_packet(AVFormatContext *s,
         case VIDEO_P_FRAME:
         case VIDEO_YOFF_P_FRAME:
         case VIDEO_I_FRAME:
-            return read_frame(vid, pb, pkt, block_type, s,
-                              s->streams[0]->codec->width * s->streams[0]->codec->height);
+            return read_frame(vid, pb, pkt, block_type, s);
 
         case EOF_BLOCK:
             if(vid->nframes != 0)