I conducted a rather interesting experiment: I wanted to find out how much CPU power really is required for MythTV's LiveTV with YUV/xv output. To eliminate any side effects I bound all Myth-related processes and interrupts (ivtv, sound, disk) exclusively to CPU#1 while running all other system tasks on CPU#0.
What I got is a so far very stable and responsive system (see end of message for some drawbacks) and these CPU measurements (top):
Cpu1 : 35.4% us, 44.7% sy, 0.0% ni, 19.9% id, 0.0% wa, 0.0% hi, 0.0% si
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ #C COMMAND
2865 mythtv 15 0 149m 27m 27m S 0.0 1.4 0:27.07 1 mythbackend
3379 root 16 0 37544 34m 22m S 58.0 1.7 507:50.14 1 XFree86
3401 mythtv 15 0 149m 60m 54m S 0.3 3.0 2:59.75 1 mythfrontend
The interrupts per second looked like this (procinfo -d -n1):
irq177: 402 ivtv0
irq185: 10 ivtv1
irq209: 12 EMU10K1
irq225: 0 3ware Storage Controller
ivtv0 is a PVR-350 running the TV-out via X/ivtvdev_drv while ivtv1 is doing the capture for liveTV. The ringbuffer lives in a tmpfs so the storage is basically idle. CPU is a 1.4 GHz PIII-S.
Maybe someone (John?, Hans?) would like to comment on the questions that came to my mind related to above data:
* Is it within expectations to use some 80% of CPU power for LiveTV / >50% for XFree86? I heard other people talk about 10-20%.
* I still get occasional jumps in the video stream. Previously I thought these were due to concurrent system activity but with this configuration I think they rather are problem #8 ("Skips in the recording") on Hans' remaining problem list.
* The sound is not 100% in sync with the video compared to real live TV (no big thing - constant and probably just a couple of ms off). This is probably MythTV related but it would be interesting if other people are seeing this too.
Any comments?
Cheers,
Martin
P.S.: LiveTV is running for 14 hours now without any ill messages either from ivtv or MythTV - no prebuffering pauses, no underruns no nothing. I will just leave it running and see if/when it breaks.
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-- Martin Rehfeld <[EMAIL PROTECTED]> some version/config info for reference: ivtv 0.3.8, ivtvdev_drv 0.10.6, kernel 2.6.8-2-686-smp stock debian (preempt + 8K stacks), HW: Dual PIII-S 1.4 GHz, 2 GB RAM |
