[mythtv-users] HDTV playback & GF4

Kent Williams kent2 at optusnet.com.au
Sat Feb 21 01:58:04 EST 2004


Well, I went out and got a GF4 MX 440 and recompiled the latest CVS with
the addition of -march-pentium4 in libavcodec.pro.

Now when trying to watch the HDTV channel, things seems much smoother
but I still get stuttering, ie, I get about a second of nice smooth
video then a short stutter, followed by a slightly garbled frame, then
another smooth second, etc, etc.

While all this is happening, CPU usage is doesn't seem to crack 50%, so
that is no longer the issue. I started to suspect the signal strength so
enabled the DVB signal monitoring for a 15 minute recording I just made
with an interval of 60 secs. I get the following:

Recording period from Sat Feb 21 17:04:00 2004 to Sat Feb 21 17:20:00
2004
Card: 6 Min SNR: 0 Avg SNR: 56574 Min BER: 426 Avg BER: 516 Cont Errs: 0
Overflows: 0

Incidentally I tried to playback a DVD using Xine and noticed a similar
problem - there were occasional pauses during playback. Perhaps the
indicates that something else is the problem.

I'm using an ASUS P4R800VM. Perhaps there are some driver / other issues
with this board and Linux?

Also, should de-interlacing filters, etc still work with XvMC?

Cheers,
Kent

-----Original Message-----
From: Andrew Dodd [mailto:atd7 at cornell.edu] 
Sent: Saturday, 21 February 2004 4:56 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] HDTV playback & GF4

Quoting Doug Larrick <doug at ties.org>:

> Kent Williams wrote:
> > Before it was 0.14, trying now with CVS.
> > Current video card is 'nVidia Corporation NV10 [GeForce 256 SDR]'
> 
> If you do 'xdpyinfo | grep XVideo' does it print anything?  Does 
> 'xvinfo' list any useable screens?
> 
> > When I add -mpentium4 to libavcodec.pro (there doesn't seem to be a
> > settings.pro in that directory), I get:
> > [compiler error]
> 
> Yeah, sorry, sleepy this morning.  It is libavcodec.pro, and the 
> directive to add is '-march=pentium4'
Note that this will only work on more recent versions of GCC.  (Not a
valid flag
on 2.9x versions, not sure if it appeared in 3.0 or later in the 3.x
series.)

The difference between -march=i686 with gcc 2.96 (RH 7.3, what my laptop
ran
until Tuesday) and -march=pentium4 with gcc 3.3.2 (Gentoo, the laptop's
new
distro) is insane...  xine can come "close" to decoding 1080i with a
GF4MX and
XvMC with only a 1.7 GHz P4-M - Dropped frames are not very common.
Previously
it was horrible.




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