[FFmpeg-devel] [PATCH] lavf/segment: add M3U8 list support

[Stefano Sabatini]

On date Wednesday 2012-08-15 17:12:30 +0200, Clément Bœsch encoded:
> On Wed, Aug 15, 2012 at 11:09:59AM +0200, Stefano Sabatini wrote:
> > Address trac ticket #1642.
> > ---
> >  libavformat/segment.c |   24 +++++++++++++++++++++++-
> >  1 files changed, 23 insertions(+), 1 deletions(-)
> > 
> > diff --git a/libavformat/segment.c b/libavformat/segment.c
> > index 744c147..35363b5 100644
> > --- a/libavformat/segment.c
> > +++ b/libavformat/segment.c
> > @@ -34,6 +34,7 @@
> >  typedef enum {
> >      LIST_TYPE_FLAT = 0,
> >      LIST_TYPE_EXT,
> > +    LIST_TYPE_M3U8,
> 
> The 8 means it will honor properly UTF-8, I guess that will be true?

I believe we adopt UTF-8 for specifying filenames if I'm not wrong,
and sure we don't use non-ASCII chars in the tags.
 
> Also, that current M3U8 implementation is an extended version of the M3U
> format, so I'm not so sure about the name. Since it's not documented, I'm
> not sure that's really important though.

I extended the docs specifying that we support the thing people call
"Extended M3U8", "flat" format should be equivalent to "plain" M3U8
lists.

> 
> >      LIST_TYPE_NB,
> >  } ListType;
> >  
> > @@ -119,6 +120,10 @@ static int segment_end(AVFormatContext *s)
> >  
> >      if (seg->list) {
> >          if (seg->list_size && !(seg->number % seg->list_size)) {
> > +            if (seg->list_type == LIST_TYPE_M3U8) {
> > +                avio_printf(seg->list_pb, "#EXT-X-ENDLIST\n");
> > +                avio_flush(seg->list_pb);
> > +            }
> >              avio_close(seg->list_pb);
> >              if ((ret = avio_open2(&seg->list_pb, seg->list, AVIO_FLAG_WRITE,
> >                                    &s->interrupt_callback, NULL)) < 0)
> > @@ -129,7 +134,17 @@ static int segment_end(AVFormatContext *s)
> >              avio_printf(seg->list_pb, "%s\n", oc->filename);
> >          } else if (seg->list_type == LIST_TYPE_EXT) {
> >              avio_printf(seg->list_pb, "%s,%f,%f\n", oc->filename, seg->start_time, seg->end_time);
> > +        } else if (seg->list_type == LIST_TYPE_M3U8) {
> > +            if (seg->number == 1) {
> > +                avio_printf(seg->list_pb, "#EXTM3U\n");
> > +                if (seg->time_str)
> > +                    avio_printf(seg->list_pb, "#EXT-X-TARGETDURATION:%f\n",
> > +                                (double)seg->time/1000000);
> 
> Are we sure the target duration won't ever be inferior to one of the
> segment duration (because of some approximation or other parameter)?

No.

> Because in that case, IIRC the spec require to get the higher value.

From:
http://tools.ietf.org/html/draft-pantos-http-live-streaming-07#section-3.3.2

|The EXT-X-TARGETDURATION tag specifies the maximum media segment
|duration.  The EXTINF duration of each media segment in the Playlist
|file MUST be less than or equal to the target duration.  This tag
|MUST appear once in the Playlist file.  It applies to the entire
|Playlist file.  Its format is:
|
|#EXT-X-TARGETDURATION:<s>
|
|where s is an integer indicating the target duration in seconds.

I'm putting the EXT-X-TARGETDURATION at the end of the file, which is
not forbidden by the specification.

> 
> > +            }
> > +            avio_printf(seg->list_pb, "#EXTINF:%f\n%s\n",
> > +                        seg->end_time - seg->start_time, oc->filename);
> 
> When I was cutting the big buck bunny sample (check in the hls.py patch
> for the exact cmd line I was using), the end_time was always the duration
> of the whole presentation, so I'm unsure about that. The workaround I used
> in the script was a diff with the start_time of the previous event.

This is unrelated with the current patch, would you mind send a patch
for that?

Patch updated (on top of the previously posted patches).
-- 
FFmpeg = Fiendish and Frenzy Majestic Perennial Esoteric Gem
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