[mythtv-users] PVR250 + TVWonder = jerky

Chad McQuinn chadmcquinn at insightbb.com
Tue Jun 3 02:14:17 EDT 2003


This is similar to the issue posted this evening with subject "PVR250 +
BT878", but different enough that I thought it deserved a new message rather
than a reply.

I have set up the following hardware over the last few days:

ASUS A7v8x-x
Athlon 2600xp+
512MB RAM
Dedicated video drive (7200RPM) with a dedicated controller
PVR-250
ATI TV-Wonder
SoundBlaster Live PCI 128 using OSS (not ALSA)
Nvidia GEForce4 MX 440 (8x AGP)

DMA is enabled on the hard drive, as is 32-bit mode. I am using Redhat 9 and
the NVidia closed-source drivers.

I am experiencing the following:

Using either JUST the PVR250 or the TV-Wonder, things seem fine (the
TV-Wonder maybe needs some tweaking, but the PVR250 works great). However,
if I try to use both tuners simultaneously, the video playback (not
recording) is extremely jumpy. This occurs whether I try to record one
program and watch live tv, or record two programs and watch one of them
(which amounts to the same thing).

The recording process itself is actually working fine; after the recording
is finished and no tuners are in use, I can watch the videos without a
problem. So, at this point you would guess that it is the hard drive not
being fast enough, but I don't think that is the case (see below). In fact I
think I can rule out any hardware or performance problems because the
following works perfectly:

* record two programs with MythTV
* play back a stream (either one being recorded now, or an old one) using
mplayer

The video coming from mplayer is extremely smooth in that case, so I don't
think this can be tied to processor, hard drive, or other hardware issues.

Here's even more evidence that it is something in myth that isn't working
correctly; if I do this:

*record two programs
*play back one of them with myth (this is jumpy)
*while that is playing, play another stream with mplayer (even one of the
currently recording streams)

then the mplayer stream is very smooth, while the stream that myth is
playing is jerky.

The relevant software settings are:

TV-Wonder set to MPEG4, 480x480, bitrate 4000, min quality 2, max 10.
Various combinations of the other flags, as well as the RTJPEG setting, have
been tried with no effect.

The PVR250 is set for 8Mb/s, dnr off.

I have tried all combinations of deinterlacing on/off and jitter reduction
on/off; while these look different, they don't have any effect on the
smoothness of the video playback.

I should also mention that the processor usage never tops 50% (in fact it is
usually much below 50%).

Any ideas?

-Chad



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