[mythtv-users] Another performance question...

[Mark Frey]

Not to add more noise on this sort of issue, but...I suppose I am going to add more noise ;)

I find myself unable to get live tv stutter-free on the following machine:

Intel P4 2.0GHz
512 MB ram
5400rpm HD (hdparm says throughput = 30MB/s, DMA is on)
NVidia GeforceFX 5200 video card with open source drivers
Latest Alsa with drivers for MAudio Delta66 soundcard
bt878 capture card, using btaudio (quite new version of bttv, whatever installed with Fedora Core)
Latest MythTV from CVS

If I try and run with the default live-TV settings (480x480, RTJpeg), I'll be fine for "talking-head" type shows (News, etc.), but sports programming (basketball for example) will cause more-or-less constant stuttering (quarter second lurches every 1 or 2 seconds). Processor usage stays near but below 50%.

I've read through all the posts I can find, and it seems like some people have no problem with performance with this spec machine, while others have trouble with even beefier machines. I'm trying to figure out what the magic is to make this work. I've instrumented the code to try and determine where my machine is falling down. So far, from what I can tell the decoder thread winds up spending alot of time waiting for the ring buffer read thread to fetch data. Whether this is because the hard drive is unable to keep up (the size on disk of each frame is bigger for sports programming because it doesn't compress as well), or because the read thread is getting starved because compression/decompression is taking alot of processor time I don't know. I'm kind of new to Linux so I don't know the best way to monitor hard drive use (any pointers?)

I've turned jitter reduction on and off, messed with the audio buffering settings, all to no avail.

My question is: Should this machine be able to do this? Are others able to get smooth playback with this sort of setup, specifically for sports programming?

Thanks for any tips anyone can offer.

-Mark
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