[mythtv-users] mythbackend is fricking frying my cpu

Jason Tackaberry tack at auc.ca
Thu Apr 10 14:32:51 UTC 2003


Note this email is largely a "me too" email. :)

On Wed, 2003-04-09 at 23:12, Wally Wallace wrote:
> I am running the latest cvs.

Me too, and I find it _really_ unstable.  I hope all the stability
problems I'm having are known and will be ironed out and that it's not
all just me. :)

> My system:

Mine is an Athlon 1400, 768M, GF2MX, 80G Seagate ST380020A (hdparm -tT:
232.7/22.5), WinTV PCI, SB Live.  using_dma, unmaskirq, and 32-bit IO.

> soundblaster live (when i try to capture the line in is noisy as hell!)

My line-in captures nicely.

> 70's show tonight. I wasn't running the frontend. Top showed 95-100% cpu
> usage! My settings are mpeg4 640x480, 3300, 2, 15, 3 and scale bitrate.
> Audio quality is 44100 and 7.

My settings are mpeg4, 640x480, 2200, max quality: 1, min quality: 3,
quality between frames: 2, audio is uncompressed at 44100.  When
recording my processor is anywhere from 50% to 85%.  This is with
mythfrontend not loaded (i.e. not watching any video).  vhq and v4mv
settings disabled since my cpu can't keep up with them.

> It seems like mpeg4 is totally fubared for my, rtjpeg works, but I built
> the system for mpeg4 cause i want good quality recordings. Same settings

This is a bit tangential, but I find even at the highest quality setting
RTjpeg yields poor quality.  Certainly I know jpeg is capable of
better.  Is there any tweaks one can do to improve this?  Or is mpeg4
the way to go for encoding?

> Every time I change channels I get frame drops for like the first
> 5-10seconds then it smooths out. This happens with mpeg4 of any
> reasonable setting but not on rtjpeg. 

A resounding "me too" on this one.  At first I thought it had to do with
the small cache on my harddisk (2MB) but your disk is much more
impressive than mine and you're still seeing the problem.

Anyone have any ideas?

> The ringbuffer seems to work for rtjpeg but not mpeg4
> I can only rewind in rtjpeg, mpeg4 says it is recording but only goes
> back 3 secs.

Mine appears to work.

>  So should i even bother with mpeg4? Everyone seems to say
> it is better, and like i said, my out of sync high cpu recordings are
> beautiful. My system should handle that right? Especially in backend
> only mode.

I think mpeg4 is the _only_ way to go, based on the quality I've seen
from RTjpeg.  Perhaps the developers just need some more time to work
out the kinks?  I'm curious to hear other people's experiences.

On another note, MythTV docs say that the processor must support SSE in
order to do deinterlacing.  According to /proc/cpuinfo, my Athlon
doesn't do SSE, yet deinterlacing works fine for me.  Are the docs out
of date?

Jason.



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