[vdr] Re: bitstreamout vs. AC3overDVB

["Dr. Werner Fink" <werner@suse.de>]

On Fri, Nov 12, 2004 at 08:05:07AM +0100, hm@seneca.muc.de wrote:
> hm@seneca.muc.de wrote:
> > In group local.ml.linux-vdr you wrote:
> > > For your timing problem: please try out 0.61f and report even if
> > > it fix your problem.  Just that I know that this fix the problem.
> 
> > OK, will do that. 
> 
> Hi Werner, I installed and tried 0.61f last night, and it seems a little
> bit better as far as AV delays. At least I don't see the ~300 ms delays any
> more. 0.61f is now at about ~50 - ~100, so that lip synchronizity is quite
> good. However I still get frequent dropouts after 15-20 minutes of
> watching. When re-starting the plugin by switching channels back and forth,
> it is okay again but the dropouts start again after 15-20 minutes. Any idea
> what this could be? 

Yep, the quart on the sound card is faster or slower than the normal time
used by the channel (e.g. Pro7). In other words, if the hardware buffer
runs empty or will be overfilled the plugin trys to recover.  In case of
a faster quart/clock the plugin knows two strategies to recover from.
The first is a full reset and the second one is to double AC3 frames
and mark one of them as an error frame (works perfect with my receiver).
In the case of a slow quart/clock, the plugin simply drops AC3
frames to hold the hardware buffer of the sound card in a playable
state.   The problem is that the PCM frame used for transport of a
AC3 frame has to exactly 6144 bytes long (aka 1536 stereo PCM samples
for 32 ms) ... you can not add or remove some of the zeros which
are used for padding the PCM frame after the nonlinear PCM data
haeder and the AC3 frame as payload.

In other word:  I guess that your sound card is slower.
Nevertheless you can try to enable VariableIO in the setup of
the plugin if you have changed that ... just in case if the
your sound card is faster.


        Werner

-- 
AC3 loop through sound card http://bitstreamout.sourceforge.net/
Howto http://www.vdr-portal.de/board/thread.php?threadid=1958
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