[mythtv-users] New pcHDTV HD-3000 driver

John Patrick Poet john at BlueSkyTours.com
Wed Dec 1 19:04:13 UTC 2004

On Tue, 30 Nov 2004, Michael S. Keller wrote:

> > This is true, if anyone has comments on if it helps, please let me know
> > and I'll forward information back to pcHDTV.  Things to watch will be
> > stuttering video caused by overloading the bus, buffer overrun or irq
> > bitmask clearing errors in dmesg or /var/log/messages.  I'm still
> > working on getting cvs/maillist up for the driver work, but I will have
> > some technical information on the card that can be published.
> The only machine I have that recognizes the HD-3000 is a P5-166 slave
> backend (My 440BX-based Celeron 1.4 GHz front/backend refuses to
> acknowledge the card's existence). getatsc runs with few or no buffer
> overruns, but I get them about once per second with MythTV, no matter
> the physical destination of the stream (local disk or NFS share).
> I get this symptom with both the 03 and 04 driver sets.

Not quite that bad for me --- With the stock CVS code, I get about one
buffer overrun every 10 seconds.

I have written a "ringbuffer thread" for hdtvrecorder which postpones the
problem.  If I am only recording one HD show, this pretty much fixes the

When I try to record two HD shows, while watching another, it will go a
few hours before getting overruns.  The problem is, once the overruns
do start happening, they are 10 times worse.

If I try recording three HD shows, while watching another, I am lucky to get
an hour before things go to hell.

With three simultaneous recordings, my system is just is not fast enough to
process the data in real time.  The ringbuffer thread allows it to process
at slightly behind real time as long as the ringbuffer does not fill up.  I
have 1 gig of RAM in this machine and have it tuned to use all it can for
the ringbuffer.  Of course, letting the ringbuffer dip into virtual memory
is very *bad*.


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