[linux-dvb] Glitches in recordings

Preston Crow pc-linuxtv05 at crowcastle.net
Wed Nov 9 03:49:35 CET 2005


On Fri, 2005-11-04 at 16:04 -0500, Preston Crow wrote:
> I'm using an old HD-2000 with a rooftop antenna and a new HD-5000 with
> digital cable QAM.  With the HD-2000, I used to get a perfect image with
> the video4linux drivers, but I switched to the DVB drivers several
> months ago, and started getting digital artifacts popping up in the
> image occasionally.  Now I also get them with the HD-5000 card, but only
> when recording HD channels; the standard-definition channels are
> perfect.

Update:  I'm now running with today's CVS DVB drivers, and as the change
in DVR_BUFFER_SIZE didn't help, that's back to the default.

If I cat from /dev/dvb/adapter0/dvr0 to a file (while running azap and
dvbtraffic, with a QAM HD channel selected), the results are different,
depending on where the file is stored.  If it's on my SATA drive, there
are occasional glitches.  If it's on my PATA drive, there are constant
glitches, and mplayer aborts when playing back the saved file after a
few seconds.  If it's on a ram disk, the image is perfect.

At this point, all I have is guesses as to the possible cause.  Perhaps
a disk-related driver is hogging the PCI bus or a kernel lock, blocking
the DVB driver, so that it isn't pulling data off of the cards fast
enough?

--PC




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