[FFmpeg-devel] how to download specific track data of a m3u8 content?

[Halley Zhao]

I tried it; but got unexpected result.
the pkt of discarded stream (stream_index) is still got from
av_read_frame().

my code is here:
https://github.com/halleyzhao/player-ffmpeg-yami/blob/m3u8/player.c

## the code piece is here:
    #define MAX_TRACK_COUNT     10
    uint32_t video_tracks[MAX_TRACK_COUNT], video_track_count = 0;
    uint32_t audio_tracks[MAX_TRACK_COUNT], audio_track_count = 0;
    for (i = 0; i < pFormat->nb_streams; i++) {
        if (pFormat->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_tracks[video_track_count++] = i;
        } else if (pFormat->streams[i]->codec->codec_type ==
AVMEDIA_TYPE_AUDIO) {
            audio_tracks[audio_track_count++] = i;
        }
        pFormat->streams[i]->discard = AVDISCARD_ALL;
    }

    if (video_track_count) {
        video_track_index = 0;
        video_stream_index = video_tracks[video_track_index];
        pFormat->streams[video_stream_index]->discard = AVDISCARD_DEFAULT;
    }
    if (audio_track_count) {
        audio_track_index = 0;
        audio_stream_index = audio_tracks[audio_track_index];
        pFormat->streams[audio_stream_index]->discard = AVDISCARD_DEFAULT;
    }
## and the result is here: video track has index 0/2/4. when I set 0 stream
to AVDISCARD_DEFAULT and 2/4 to AVDISCARDALL, the pkt with stream_index 2/4
still reach me.
  player.c, 114, got pkt with stream_index: 0
  player.c, 114, got pkt with stream_index: 2
  player.c, 114, got pkt with stream_index: 4
  player.c, 114, got pkt with stream_index: 0
  player.c, 114, got pkt with stream_index: 2
  player.c, 114, got pkt with stream_index: 4
  player.c, 114, got pkt with stream_index: 0
  player.c, 114, got pkt with stream_index: 2
  player.c, 114, got pkt with stream_index: 3
  player.c, 114, got pkt with stream_index: 3
  player.c, 114, got pkt with stream_index: 4
  player.c, 114, got pkt with stream_index: 5
  player.c, 114, got pkt with stream_index: 5

2016-06-29 19:25 GMT+08:00 aihua zhao <aihua.halley.zhao at gmail.com>:

> thanks, seems the right clue to follow.
>
> I don't know much about ffmpeg, after went through avplay.c. I think I
> should do the following steps
> 1. discard all stream by default.
>   refer to decode_thread()
>     for (i = 0; i < ic->nb_streams; i++)
>         ic->streams[i]->discard = AVDISCARD_ALL;
> 2. enable the desired stream only
> refer to stream_component_open()
>             ic->streams[stream_index]->discard = AVDISCARD_DEFAULT;
>
> thanks for your help.
>
> 2016-06-29 10:01 GMT+08:00 Steven Liu <lingjiujianke at gmail.com>:
>
>> 2016-06-29 8:36 GMT+08:00 aihua zhao <aihua.halley.zhao at gmail.com>:
>>
>> > thanks.
>> >
>> > Yes, readahead the list is must.
>> > but during playback, I found ffmpeg downloads each content of the list
>> > -- av_read_frame() returns me each content with different stream_index.
>> > I'm expecting av_read_frame() returns me the interested stream only.
>> > I haven't found a way to do so; or said, is there ffmpeg interface to
>> > specify a dedicate stream (stream_index) to download.
>> >
>> > i'm looking into hls.c; there is recheck_discard_flags(), seems it is
>> > designed to do some policy like this.
>> > but I haven't found one top level interface of ffmpeg for it.
>> > recheck_discard_flags() is called once only during hls_read_packet()
>> when
>> > c->first_packet is set  -- this flag is set in hls_read_header() only.
>> >
>> >
>> > 2016-06-28 22:22 GMT+08:00 Steven Liu <lingjiujianke at gmail.com>:
>> >
>> > > 2016-06-28 14:26 GMT+08:00 aihua zhao <aihua.halley.zhao at gmail.com>:
>> > >
>> > > > Hi Experts:
>> > > >
>> > > > I use ffmpeg to parse/demux media content, and created a player
>> basing
>> > on
>> > > > it.
>> > > >
>> > > > here is a m3u8 content:
>> > > >
>> > > >
>> > >
>> >
>> http://asp.cntv.lxdns.com/asp/hls/main/0303000a/3/default/438eb7a818b246c187e72f1cd4e1bc4c/main.m3u8
>> > > > <
>> > > >
>> > >
>> >
>> http://asp.cntv.lxdns.com/asp/hls/main/0303000a/3/default/438eb7a818b246c187e72f1cd4e1bc4c/main.m3u8?maxbr=1200
>> > > > >
>> > > > there are three video track in it.
>> > > >
>> > > > I found all video/audio tracks are downloaded during playback, and I
>> > can
>> > > > switch different track on the fly.
>> > > > however, it consumes much bandwidth since all tracks are downloaded.
>> > > >
>> > > > even when I append bandwidth to the url; still the same result:
>> > > >
>> > > >
>> > >
>> >
>> http://asp.cntv.lxdns.com/asp/hls/main/0303000a/3/default/438eb7a818b246c187e72f1cd4e1bc4c/main.m3u8?maxbr=1200
>> > > >
>> > > > Is there any way to download the specified track only to save
>> > bandwidth?
>> > > >
>> > > > thanks
>> > > >
>> > >
>> > > Hi Aihua Zhao,
>> > >
>> > >       If you haven't read the m3u8 file and parse the playlist, and
>> read
>> > > the sub m3u8 playlist, how do you get the info of the mpegts?
>> > >
>> > >       So it's must readahead the list and list all of the track for
>> > choose.
>> > you mean the function looks like "stream_cycle_channel" in ffplay?
>> >
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>> ffmpeg-devel at ffmpeg.org
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>>
>
>