[mythtv-users] Stuttery playing back BBC HD
Paul.Fowler at reuters.com
Tue Jan 2 12:42:39 UTC 2007
I have been experimenting with BBC-HD and have got to the point where I
need to re-check some of my assumptions because although I get
beautifult crisp pictures, I am not getting full frame rate. Furthermore
it is not like I am getting every other frame dropped, I seems to run
happy for about 8 frames at a time then pauses for about a half second.
My hardware is (in my experimental system):
CPU: Athlon 2400+
Motherboard: Abit NF2-s Nforce 2
RAM: 768MB DDR mixture of PC2700 (256MB) and PC3200 (512MB)
Hard Disk: 80GB (hdparm -t /dev/had reports 45MB/s) on 80wire cable
Tuner card: Twinham VP1020A satellite pci card (latency_timer = 32)
Video card: Nvidia FX5200 64MB AGP (latency_timer = 248 - not sure if
OS: Fedora Core 4 latest kernel 2142
I admit this is a bit of a hotch potch of parts, but I wanted to proove
this out first.
Using MythTV 0.20 I get the same stuttering whether using standard,
libmpeg2 or nvidia_xvmc
I have the nvidia driver installed from atrpms (7676 I think??)
My present concerns are:
1) can the twinhan card handle the symbol rate which BBC-HD uses (not
sure how to test this)
so far I have tried playing the recorded files (eg Planet Earth
8.6GB/Hour!) on various machines including a P4HT 2.8GHz and still
cannot get the full frame rate - eg. I am not sure if the disk files are
2) I believe my hard disk is fast enough (although ridiculously small)
on this test machine, but not sure if ext3 filing system is killing
3) probably the CPU is not fast enough.
4) I know XVMC is working, but not sure if it is helping me with H264
transport streams ?
I have tried fiddling with latency timers, I believe my hard drive speed
is up to it. I have done chmod a+s on /usr/bin/mythfrontend. I have
added group mythtv to /etc/security/limits.conf to try and establish
realtime priority (but think I need @mythtv rather than @audio, but as I
do not know much about users/groups I have probably done that wrong).
I plan to try szap "BBC-HD" and dvbstream | mplayer soon to see what is
possible, and to try mplayer with -benchmark.
Can anybody suggest an in-expensive adjustments I could make, or other
things I could check.
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