[mythtv-users] mythbackend is fricking frying my cpu

[Joseph H. Fry]

I could be way off base here, but wouldn't a MPEG4 Variable Bit Rate
real time encoder always use 100% of available processor.  The way I
understand it is that the encoder is trying to compress the video in
real time as much as it possibly can thus using all of the available
clock cycles.  If you look at the file sizes of files encoded with the
frontend off vs with the front end on, you should notice a significant
difference in the amount of disk space consumed for a given length of
video.  In otherwords... your cpu runs at max capacity when encoding and
depending upon how many cycles are used by other processes the level of
compression will vary.

I hope this makes sense, it's late and I'm tired... but as far as I
understand it this is the way most realtime VBR encoders work.  Or isn't
the MPEG4 encoder VBR?

Joe

-----Original Message-----
From: mythtv-users-bounces at snowman.net
[mailto:mythtv-users-bounces at snowman.net] On Behalf Of Wally Wallace
Sent: Wednesday, April 09, 2003 11:12 PM
To: mythtv-users at snowman.net
Subject: [mythtv-users] mythbackend is fricking frying my cpu

I am running the latest cvs. 
My system:
athlon 2100+ overclocked to 2.1ghz
512mb ddr ram
geforce2mx
asus a7v266 board
wd 200gb 8mb cache drive
	hdparm -tT gives 270/51
wintv 401 (i think - bought used) with btaudio working for digital and
analog
avertv stereo (btaudio only for analog which sucks)
onboard cmedia sound
soundblaster live (when i try to capture the line in is noisy as hell!)

Using btaudio with my wintv card I tried to record 3 episodes of that
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.
I know my system should handle this!!!! I specced it specifially to do
high quality recording. I will overclock my cpu even more when I get a
better hs/fan.
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
with rtjpeg gives me 60-70% cpu which is also too friggin high. The
worst part is, when I do live tv with the same setting cpu usage is at
100% for mpeg4, but backend is only 70-80 and frontend takes the rest.
Now that makes no since, cause in record only backend takes all my cpu!

So i can view those mpeg4 recordings, and they look beautiful but
audio/bisual is way messed up and i get constant -
Audio buffer overflow, audio data lost!
The video is rushed too, by like 20-30% so peoples lips move really
fast.

Next problem:
I get a very annoying poping sound whenever i change channels. Channel
changing also takes at least 500ms.

Next problem:
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. 

Next problem:
I hit v for pip and my audio gets very choppy and drops every other
frame. This seems to just happen with rtjpeg!

Next problem:
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.

 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 just did some more tests. Even 480x480 mpeg4 uses all my cpu and 
gives me:
Audio buffer overflow, audio data lost!
This also happened when viewing the mpeg4 recordings.

Thanks for any insight.
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