[FFmpeg-devel] [PATCH] lavf/segment: add reference_stream option

[Alexander Strasser]

Hi Stefano,

Stefano Sabatini wrote:
> On date Wednesday 2012-12-26 19:39:50 +0000, Paul B Mahol encoded:
> > On 12/22/12, Stefano Sabatini <stefasab at gmail.com> wrote:
[...]
> > > diff --git a/libavformat/segment.c b/libavformat/segment.c
> > > index dc9b9c8..b46de10 100644
> > > --- a/libavformat/segment.c
> > > +++ b/libavformat/segment.c
[...]
> > >
> > > -    for (i = 0; i < s->nb_streams; i++)
> > > -        seg->has_video +=
> > > -            (s->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO);
> > > +    seg->reference_stream_index = -1;
> > > +    if (!strcmp(seg->reference_stream_specifier, "auto")) {
> > > +        int first_id[AVMEDIA_TYPE_NB];
> > > +
> > > +        for (i = 0; i < AVMEDIA_TYPE_NB; i++)
> > > +            first_id[i] = -1;
> > > +
> > > +        for (i = 0; i < s->nb_streams; i++) {
> > > +            enum AVMediaType type_priority_list[] = {
> > 
> 
> > static const?
> 
> Will fix it.
> 
> > Move somewhere else?
> 
> I'd prefer to keep it in context.

  What about this (sorry neither compiled nor tested):

/* higher value higher priority, 
   types not explicitly initialized will never be selected */
static const int media_type_priority[AVMEDIA_TYPE_NB] = {
  [AVMEDIA_TYPE_VIDEO]      = 5,
  [AVMEDIA_TYPE_AUDIO]      = 4,
  [AVMEDIA_TYPE_SUBTITLE]   = 3,
  [AVMEDIA_TYPE_DATA]       = 2,
  [AVMEDIA_TYPE_ATTACHMENT] = 1
};

int cur_reference_prio = 0;

for (i = 0; i < s->nb_streams; ++i) {
   enum AVMediaType media_type = s->streams[i]->codec->codec_type; 
   int prio;

   if (media_type < 0 || media_type >= AVMEDIA_TYPE_NB) {
     continue;
   }
   prio = media_type_priority[media_type];

   if (prio > cur_reference_prio) {
      seg->reference_stream_index = i;
      cur_reference_prio = prio;
   }
}

> 
> > Is this actually used?
> 
> See below.
> 
> > 
> > > +                AVMEDIA_TYPE_VIDEO,
> > > +                AVMEDIA_TYPE_AUDIO,
> > > +                AVMEDIA_TYPE_SUBTITLE,
> > > +                AVMEDIA_TYPE_DATA,
> > > +                AVMEDIA_TYPE_ATTACHMENT
> > > +            };
> > > +            enum AVMediaType type = s->streams[i]->codec->codec_type;
> > > +            first_id[type] = FFMAX(first_id[type], i);

  Would the FFMAX here usually work as expected?

> > > +
> > > +            for (i = 0; i < FF_ARRAY_ELEMS(type_priority_list); i++)
> > > +                if ((seg->reference_stream_index = first_id[i]) >= 0)
> > > +                    break;
> > > +        }
> [...]


  Alexander