[linux-dvb] Re: AW: Re: VDR and DVD with pause -> noise corrupt

["Jean-Claude REPETTO" <jrepetto@francenet.fr>]

----- Original Message -----
From: Andreas Schultz <aschultz@warp10.net>
To: Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>
Cc: Linux-Dvb <linux-dvb@linuxtv.org>
Sent: Tuesday, August 21, 2001 3:21 AM
Subject: [linux-dvb] Re: AW: Re: VDR and DVD with pause -> noise corrupt


> Klaus Schmidinger wrote:
> > Ralph Metzler wrote:
> >
> >>Klaus Schmidinger writes:
> >> > Ralph Metzler wrote:
> >> > >
> >> > > Klaus Schmidinger writes:
> >> > >  > If the audio frames don't contain a PTS, it's no wonder they get
out of sync
> >> > >  > (even in normal replay video and audio gets out of sync after
some time).
> >> > >
> >> > > They should not any longer after my last firmware syncing patch
> >> > > about 10 days ago. This patch no longer was a workaround for the
> >> > > "jerking picture bug", which would just sync audio/video at the
start
> >> > > of playback, but a complete fix. Syncing is always on now.
> >> >
> >> > I just replayed a DVD with the latest versions of both driver and
VDR,
> >> > but after a while video and audio ran out of sync (audio was about
half
> >> > a second early). I'm not talking about external AC3 replay, but
"internal"
> >> > replay of both audio and video via the DVB card (converted by the
'ac3dec'
> >> > that comes with VDR).
> >> >
> >> > Do others also experience this, or is it just me?
> >> >
> >> > >  > Is there a way to have ac3dec generate the necessary PTS for the
audio frames?
> >> > >  > The original Dolby Digital frames that ac3dec uses to generate
the "normal"
> >> > >  > audio frames must, I believe, contain a PTS, don't they?
> >> > >
> >> > > Of course they contain the correct PTS but reinserting it would not
> >> > > help because the decoder hardware does not support syncing for PCM
sound.
> >>
> >>But you were talking about "normal replay" which I understood to mean
> >>normal MPEG2 video and MPEG audio.
> >>As I already wrote above, there is no syncing if using PCM. So, I am not
> >>surprised that sync is lost.
> >>Or does your ac3dec convert to MPEG audio? If it does, does it insert
> >>the proper PTSs?
> >>
> >>Ralph
> >>
> >
> > Maybe Andreas (Schultz) or Matjaz (Thaler) can comment on this.
> > I haven't looked into the ac3dec version that was provided by
> > Andreas and Matjaz yet.
>
> Klaus, could you try to increase the frame buffer size in ac3dec? It's
> in ac3.h:
> #define AC3_BUFFER_SIZE (6*1024*16)
>
> I have been using (16*1024*16) for some experiments and this solved the
> audio jitter during fast moving scences problem. Maybe, audio starts
> lagging due to lost AC3 frames, or is it to early???
>
> Andreas

I have tried this patch, but it seems that nothing is changed. The audio
comes out of sync :
- after a pause
- after several language changes

BTW, I have DVDs with a MPEG audio track. Should it be possible to support
them in VDR ? It would be interesting to see if there are the same problems,
since the MPEG audio should contain PTSs.

Jean-Claude






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