On 04/11/15 00:29, 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 | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> Uncrustify
> 
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index 572e781..a6a9d09 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2285,10 +2285,20 @@ 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) {
> +            AVDictionaryEntry *fallback;
> +            fallback = av_dict_get(track->st->metadata, "fallback", NULL, 0);
> +            if (fallback != NULL) {
> +                int index = strtol(fallback->value, NULL, 0);
> +                if (index >= 0 && index < mov->nb_streams) {
> +                    track->tref_tag = MKTAG('f','a','l','l');
> +                    track->tref_id = mov->tracks[index].track_id;
> +                }
> +            }
>          }
>      }
>  
> 

Martin, if it is ok for you I'd get this in tonight.

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