libavformat/avienc: Fix duration of audio segment in OpenDML master index

Fixes the duration field of the OpenDML master index "indx" chunk to
contain the number of samples instead of the number of packets for
(linear/PCM) audio streams.

This matches the OpenDML V1.02 standard text which states that the
duration field shall contain "time span in stream ticks".
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avienc.c

@@ -49,6 +49,7 @@ typedef struct AVIIentry {
 
 typedef struct AVIIndex {
     int64_t     indx_start;
+    int64_t     audio_strm_offset;
     int         entry;
     int         ents_allocated;
     AVIIentry** cluster;
@@ -66,6 +67,7 @@ typedef struct AVIStream {
     int packet_count;
     int entry;
     int max_size;
+    int sample_requested;
 
     int64_t last_dts;
 
@@ -91,6 +93,7 @@ static int64_t avi_start_new_riff(AVFormatContext *s, AVIOContext *pb,
     avi->riff_id++;
     for (i = 0; i < s->nb_streams; i++) {
         AVIStream *avist = s->streams[i]->priv_data;
+        avist->indexes.audio_strm_offset = avist->audio_strm_length;
         avist->indexes.entry = 0;
     }
 
@@ -476,6 +479,7 @@ static int avi_write_ix(AVFormatContext *s)
     for (i = 0; i < s->nb_streams; i++) {
         AVIStream *avist = s->streams[i]->priv_data;
         int64_t ix, pos;
+        int au_byterate, au_ssize, au_scale;
 
         avi_stream2fourcc(tag, i, s->streams[i]->codec->codec_type);
         ix_tag[3] = '0' + i;
@@ -511,7 +515,16 @@ static int avi_write_ix(AVFormatContext *s)
         avio_skip(pb, 16 * avi->riff_id);
         avio_wl64(pb, ix);                    /* qwOffset */
         avio_wl32(pb, pos - ix);              /* dwSize */
-        avio_wl32(pb, avist->indexes.entry);  /* dwDuration */
+        ff_parse_specific_params(s->streams[i], &au_byterate, &au_ssize, &au_scale);
+        if (s->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO && au_ssize > 0) {
+            uint32_t audio_segm_size = (avist->audio_strm_length - avist->indexes.audio_strm_offset);
+            if ((audio_segm_size % au_ssize > 0) && !avist->sample_requested) {
+                avpriv_request_sample(s, "OpenDML index duration for audio packets with partial frames");
+                avist->sample_requested = 1;
+            }
+            avio_wl32(pb, audio_segm_size / au_ssize);  /* dwDuration (sample count) */
+        } else
+            avio_wl32(pb, avist->indexes.entry);  /* dwDuration (packet count) */
 
         avio_seek(pb, pos, SEEK_SET);
     }