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[linux-dvb] Re: dvb-kernel TS continuity errors



Klaus Schmidinger wrote:
> 
> I'm currently testing VDR under kernel 2.6 with the dvb-kernel
> driver (version from linuxtv.org CVS as of 2004-09-10).
> 
> When I run 5 parallel recordings on the same transponder
> (RTL, RTL 2, Super RTL, VOX and RTL Shop) it works just fine on a full
> featured DVB card, while I get TS continuity errors when I
> do the same thing on a WinTV NOVA-S budget card.
> 
> What makes this so strange is that normally it is said that
> a _budget_ card can deliver the full TS, while a full featured
> card is limited in what it can deliver. In this scenario it would
> appear that the FF card works better than a budget card.
> 
> Could it be that there is a bug in the budget card driver
> that causes problems with multiple recordings from the same
> transponder (which means high data transfer rate)?
> 
> Note that with two recordings on the budget card (RTL and RTL 2)
> I don't get these problems. The more recordings I run on the same
> budget card, the more TS continuity errors I get. On the FF card
> with 5 recordings I don't get a single continuity error. Needless
> to say that the recordings where the continuity errors happened are
> broken (video and audio artefacts), while those made with the FF card
> are perfectly fine.
> 
> Also, during all these tests there were no buffer overflows in VDR,
> and also none in the driver (at least none that were reported by the
> read() call).
> 
> One observation is that with 5 recordings the FF card typically returns
> some 30KB in one read(), while the budget card delivers around 4KB per
> read(). So with the budget card there are apparently a lot more read()
> calls. Don't know whether this constitues a problem, though.
> 
> Any ideas what could be causing this?
> 
> Klaus

I just realized that the dvb-kernel driver apparently numbers the
devices differently than the old DVB driver did. With the old driver
I had the following device sequence

  0  FF card
  1  budget card
  2  FF card

while with dvb-kernel I have

  0 FF card
  1 FF card
  2 budget card

I became aware of this when I was wondering why my CAM was detected
at the "second" card, while it is physically attached to the "third"
card (as seen by the old driver).

So what I wrote above is apparently wrong - the budget card does deliver
a flawless data stream, even with 5 parallel recordings. It's the FF card
that has the problems.

Klaus




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