[vlc-devel] [PATCH] VLC unable to play HLS live stream

Avishay Spitzer savishay at gmail.com
Wed Aug 14 15:25:38 CEST 2013


Ilkka,

> In what kinda conditions you can reproduce that issues that hls modules
has no data while it should have?

Try the following stream:
http://www.nasa.gov/multimedia/nasatv/NTV-Public-IPS.m3u8.

It's a live stream unencrypted (each playlist contains 8 segments) so it
will not work with official VLC version due to the download issue I fixed.

Without the TS patch, at least with my network connection, the stream stops
after a while because of delays. With the fix in TS module I was able to
play this stream continuously for more than 2 hours with no problem.

I agree that it would be better to fix this problem within the HLS module,
but I didn't find a way to achieve that and I honestly doubt that it's
possible (however, I'm new to VLC so of-course I might be wrong).

Regards,
Avishay


On Wed, Aug 14, 2013 at 9:09 AM, Ilkka Ollakka <ileoo at videolan.org> wrote:

> On Wed, Aug 14, 2013 at 09:04:13AM -0400, Avishay Spitzer wrote:
> > Ilkka,
>
> Hi,
>
> > The problem in TS module, is that once HLS module (HTTPLive stream
> filter)
> > has no data, TS will think that it has reached EOF and VLC will stop
> > playing.
>
> In what kinda conditions you can reproduce that issues that hls modules
> has no data while it should have?
>
> > I don't think that it can be solved from within the HLS module because
> HLS
> > has no control over this. I think that TS module should treat these
> > situations gracefully and retry (as I implemented).
>
> > If you have another idea please let me know.
>
> in git-tree some places in HLS module assume that segments are 10sec
> length and that can cause some issues. I have changed those but haven't
> yet pushed them as haven't got time to test them properly
>
> > Regards,
> > Avishay
>
>
>
> > On Wed, Aug 14, 2013 at 8:37 AM, Ilkka Ollakka <ileoo at videolan.org>
> wrote:
>
>
> > > I think this patch tries to fix issue in wrong place. If the problem is
> > > in HLS slow start or short HLS playlists, issue should be handled in
> > > httplive stream filter.
>
> > > On Wed, Aug 14, 2013 at 04:13:46AM -0400, Avishay Spitzer wrote:
> > > > From 15f5f247e783895e95020e4f0529bd112bf77b6d Mon Sep 17 00:00:00
> 2001
> > > > From: Avishay Spitzer <savishay at gmail.com>
> > > > Date: Wed, 14 Aug 2013 03:52:44 -0400
> > > > Subject: [PATCH 1/3] In case of slow connections or short HLS
> playlists,
> > > >  packets may not arrive on time and TS module will
> > > >  declare EOF which will case VLC to stop playing the
> > > >  stream. Problem was solved by adding a retries
> > > >  mechanism with increasing backoff.
>
> > > > ---
> > > >  modules/demux/ts.c |   37 ++++++++++++++++++++++++++++++++++++-
> > > >  1 file changed, 36 insertions(+), 1 deletion(-)
>
> > > > diff --git a/modules/demux/ts.c b/modules/demux/ts.c
> > > > index 5c4a288..dd74e36 100644
> > > > --- a/modules/demux/ts.c
> > > > +++ b/modules/demux/ts.c
> > > > @@ -334,6 +334,9 @@ struct demux_sys_t
>
> > > >      /* */
> > > >      bool        b_start_record;
> > > > +
> > > > +    /* Counts number of times ReadTSPacket returned NULL for
> > > implemeting a retries mechanism */
> > > > +    uint64_t         b_get_packet_retry;
> > > >  };
>
> > > >  static int Demux    ( demux_t *p_demux );
> > > > @@ -570,6 +573,9 @@ static int Open( vlc_object_t *p_this )
> > > >      p_sys->i_packet_size = i_packet_size;
> > > >      vlc_mutex_init( &p_sys->csa_lock );
>
> > > > +    // Initialize retries counter
> > > > +    p_sys->b_get_packet_retry = 0;
> > > > +
> > > >      p_sys->buffer = NULL;
> > > >      p_demux->pf_demux = Demux;
> > > >      p_demux->pf_control = Control;
> > > > @@ -949,9 +955,38 @@ static int Demux( demux_t *p_demux )
> > > >          block_t     *p_pkt;
> > > >          if( !(p_pkt = ReadTSPacket( p_demux )) )
> > > >          {
> > > > -            return 0;
> > > > +             // Retries mechanism - start
> > > > +             // In case of live streams TS packets may delay due to
> > > slow connections or short
> > > > +             // playlists (in case of HLS).
> > > > +             // We don't want to declare EOF (by returning 0 here)
> > > right away so we add a retries
> > > > +             // mechanism with increasing backoff.
> > > > +             // Retries are limited to 100 retries per packet and
> since
> > > backoff is based on an
> > > > +             // arithmetic progression the aggregate waiting time
> until
> > > declaring EOF is
> > > > +             // 100*(100+1)/2=5050ms.
> > > > +             // In order to make the stream continuous after
> reaching
> > > 100 retries each backoff
> > > > +             // will last 100ms and EOF will not be declared.
> > > > +
> > > > +             // If 100 retries failed then kill this stream to avoid
> > > VLC getting stuck
> > > > +             if (!(vlc_object_alive (p_demux)))
> > > > +                     return 0;
> > > > +
> > > > +             // Increase the retries count before sleeping (avoids
> 0ms
> > > sleep)
> > > > +             p_sys->b_get_packet_retry++;
> > > > +
> > > > +             // Sleep for 1ms times the retries counter before
> returning
> > > > +             msleep(((p_sys->b_get_packet_retry >= 100) ? 100 :
> > > p_sys->b_get_packet_retry) * 1000);
> > > > +
> > > > +             // If the vlc object is not alive after sleeping get
> out
> > > > +             if (!(vlc_object_alive (p_demux)))
> > > > +                     return 0;
> > > > +             // Retries mechanism - end
> > > > +
> > > > +             return 1;
> > > >          }
>
> > > > +     // If packet was received correctly zero retries counter
> > > > +     p_sys->b_get_packet_retry = 0;
> > > > +
> > > >          if( p_sys->b_start_record )
> > > >          {
> > > >              /* Enable recording once synchronized */
> > > --
> > > Ilkka Ollakka
> > > There's an old proverb that says just about whatever you want it to.
>
> > > _______________________________________________
> > > vlc-devel mailing list
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>
>
>
> --
> Ilkka Ollakka
> I've been in more laps than a napkin.
>                 -- Mae West
>
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>
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