[vlc-devel] Re: lip sych problem

[serkan bozkurt]

Hi to all,
A have 2 questions,

1-)Why bad presentation times in the ES's results in
audio and video synch. problem in RTP streaming.

2-)If this presentation  times are bad why players do
not have any sych problems between different medias.

Best Ragards....


--- serkan bozkurt <serkanboz80 at yahoo.com> wrote:

> Hi DJ,
> 
> I have a questions :
> 
> You are saying that "player plays broken mpg's but
> it
> does not mean it is streamable".
> 
> Can you please explain about in more detail.
> 
> Best Regards..
> 
> --- Derk-Jan Hartman <hartman at videolan.org> wrote:
> 
> > On 28-nov-2005, at 0:14, Ross Finlayson wrote:
> > >> Should add here - RTP streams are actually 2
> (at
> > least) different  
> > >> streams
> > >> with different payloads
> > >
> > > This is correct.
> > >
> > >> that are not syncronised well (look at live555
> > >> mailing list). I.e - system will "sync on
> average
> > bitrate", not on  
> > >> each
> > >> video packet. It means, that LiveMedia free
> > library do not contain
> > >> mechanisms to make A/V sync/resync.
> > >
> > > But this is all completely false.  See
> > <http://www.live555.com/ 
> > > liveMedia/faq.html#separate-rtp-streams>
> > >
> > > Once again: If your original data source (at the
> > server end) has  
> > > (i) proper presentation times (corresponding to
> > the 'wall clock'  
> > > time generated by calling "gettimeofday()"), and
> > (ii) it properly  
> > > implements RTCP, then RTSP/RTP clients that use
> > the "LIVE555  
> > > Streaming Media" software - including VLC -
> *will*
> > get correct,  
> > > time-synchronized presentation times.
> > >
> > > If, however, your server does not implement
> RTCP,
> > and/or does not  
> > > use properly synchronized presentation times to
> > begin with, then  
> > > you're SOL.  End of story.
> > >
> > > I spent a lot of time making sure that the
> LIVE555
> > RTP/RTCP  
> > > implementation works properly - to generate
> > correct, time- 
> > > synchronized presentation times at the client
> end.
> >  I wish people  
> > > would stop claiming that this doesn't work.
> > 
> > The problem here is that there is tons of material
> > in the wild that  
> > does NOT have proper timestamping and
> > synchronisation. The fact that  
> > lots of this material works in most players, does
> > not mean it is per  
> > definition streamable. The fact is the file is
> > BROKEN. People need to  
> > understand this. For MPEG material, like 85% is
> > probably broken.
> > 
> > DJ
> > 
> > -- 
> > This is the vlc-devel mailing-list, see
> > http://www.videolan.org/vlc/
> > To unsubscribe, please read
> > http://developers.videolan.org/lists.html
> > 
> > 
> 
> 
> 
> 	
> 		
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