[linux-dvb] Re: A/V disturbances while recording (was:Today's CVS driver)

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

"Marcus O.C. Metzler" wrote:
> 
> Klaus Schmidinger writes:
>  > I did a few tests with today's CVS driver, but it turned out to have
>  > severe problems with tuning channels and recording. A sample recording
>  > from 3sat had heavy video and audio distortions. After switching back
>  > to the previous driver version (2001-05-17) and recording the rest of the same
>  > broadcast ("nano"), that part of the recording was ok.
>  >
> Maybe you have problems with the new PES packets which have some
> stuffing bytes to improve debi transfer (alignment).
> We have no problems with recording or playback here.

I just made the following experiment:

My third DVB card recorded the current ZDF programme, while the first card
immediately replayed the recorded data. My tv set is able to do PIP
(picture in picture), so I was able to view the live signal from the AV output
of the third card as well as the replayed signal from the first card (with a few
seconds delay).

Much to my surprise the audio disturbances and video artifacts happened on the
*LIVE* signal - the recording just repeated what it had received earlier.

Another test with 3sat showed the same errors in the *LIVE* signal.

I then recorded 3sat with my third card and also tuned to 3sat on my first
card, thus having the live picture on both a card that is currently recording
and one that is just showing the programme. As I already expected, the disturbances
happened only on the card that was recording.

I double checked this with the CVS driver version 2001-05-17, where during several
minutes of testing I have observed only one such disturbance. So it would appear that
this has become a lot worse between CVS driver versions 2001-05-17 and 2001-05-25.

Whether or not such disturbances happen apparently depends on what kind of
programme is currently broadcast. There are times when (even with the latest driver)
I can't observe any errors for several minutes, and other times when they occur every
few seconds. It would appear that 3sat is a good test candidate, and here especially
the "nano" programme. But also the ZDF shows this behaviour.

Can anybody else reproduce these effects?

Can the driver developers think of anything that might cause this?
I don't think that the *live* signal should be affected by the fact that
the card is recording!?

Am I doing something wrong here?

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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