[3/3] movenc: add fallback audio track tref support

Message ID 1446745744-22977-3-git-send-email-stebbins@jetheaddev.com
State New
Headers show

Commit Message

John Stebbins Nov. 5, 2015, 5:49 p.m.
This feature allows making associations between audio tracks
that apple players recognize.  E.g. when an ac3 track has a
tref that points to an aac track, devices that don't support
ac3 will automatically fall back to the aac track.

Apple used to *guess* these associations, but new products
(AppleTV 4) no longer guess and this association can only
be made explicitly now using the "fall" tref.
---
 libavformat/movenc.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

Comments

Luca Barbato Nov. 5, 2015, 11:26 p.m. | #1
On 05/11/15 18:49, John Stebbins wrote:
> This feature allows making associations between audio tracks
> that apple players recognize.  E.g. when an ac3 track has a
> tref that points to an aac track, devices that don't support
> ac3 will automatically fall back to the aac track.
> 
> Apple used to *guess* these associations, but new products
> (AppleTV 4) no longer guess and this association can only
> be made explicitly now using the "fall" tref.
> ---
>  libavformat/movenc.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)

Fine for me, Martin and Anton?

lu

Patch

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 572e781..594d464 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -2285,10 +2285,21 @@  static int mov_write_moov_tag(AVIOContext *pb, MOVMuxContext *mov,
             mov->tracks[i].tref_id  = mov->tracks[mov->chapter_track].track_id;
         }
     for (i = 0; i < mov->nb_streams; i++) {
-        if (mov->tracks[i].tag == MKTAG('r','t','p',' ')) {
-            mov->tracks[i].tref_tag = MKTAG('h','i','n','t');
-            mov->tracks[i].tref_id =
-                mov->tracks[mov->tracks[i].src_track].track_id;
+        MOVTrack *track = &mov->tracks[i];
+        if (track->tag == MKTAG('r','t','p',' ')) {
+            track->tref_tag = MKTAG('h','i','n','t');
+            track->tref_id = mov->tracks[track->src_track].track_id;
+        } else if (track->enc->codec_type == AVMEDIA_TYPE_AUDIO) {
+            int * fallback, size;
+            fallback = (int*)av_stream_get_side_data(track->st,
+                                                     AV_PKT_DATA_FALLBACK_TRACK,
+                                                     &size);
+            if (fallback != NULL && size == sizeof(int)) {
+                if (*fallback >= 0 && *fallback < mov->nb_streams) {
+                    track->tref_tag = MKTAG('f','a','l','l');
+                    track->tref_id = mov->tracks[*fallback].track_id;
+                }
+            }
         }
     }