[mythtv-users] Performance problem

[Raphael Pooser]

Ryan Duffy wrote:
> Jonas Björklund wrote:
>   
>> Hello,
>>
>> On Sun, 14 May 2006, Raphael Pooser wrote:
>>
>>     
>>>> I have a RS482-IL motherbord and a AMD Turion MT-34.
>>>> The motherbord has a ATI Radeon Xpress 200 built in.
>>>> I have Hauppauge bt848. Samsung Spinpoint 250GB harddisk.
>>>>
>>>> I have only tried live TV and get performance problem. Every 2 seconds I
>>>> get a lag on the picture. :-(
>>>>
>>>> Is my system to slow? CPU? Capture card? Harddisk?
>>>>
>>>>         
>>> I would put the problem at none of the above, and move it on to your
>>> graphics card.
>>> At least when I first installed the drivers for my ATI card, it wasn't
>>> even using XV, causing it to eat up 60% of the processor just to watch a
>>> 640x480 stream, and with a software encoder taking about 40% to capture
>>> it, I was getting pauses exactly like the ones you're getting.  After
>>> making sure I had XV working, I got around 5% to watch a stream by
>>> itself, and closer to 50% to watch something live or watch and record at
>>> the same time.
>>> So I would give your graphics card driver a look.  Are you using fglrx?
>>> If so, make sure your vendor string for OGL reads ATI and not mesa, or
>>> XV won't be working either.
>>> I've heard that XV works perfectly when using "ati" in X, but I don't
>>> think "ati" supports the xpress 200, not 100% sure.
>>> Also, "ati" won't let you use TV out.
>>> Raphael
>>>       
>
> I see this problem too. 
> I really don't think its a CPU problem (I've got a 4400+ X2) and my CPU is barely troubled during playback.
>
> I have a workaround for the problem, which is to pause liveTV for a few seconds and then play. That solves the problem - I've never had any problem in playing pre-recorded shows.
>
> This makes me think it is probably caused by buffering somewhere, since we have one process writing the stream to disk as it arrives, and another reading the stream and playing it. Obviously, if the writing stream only flushes to disk every couple of seconds, then the reading stream will be forced to pause if it runs out of data and has to wait for the next flush. 
>
> Of course, your problem may be different to mine...
>
>   

Hmm that's interesting.  In that case it wouldn't be playback that's the 
problem, unless the playback is using such high cpu time that there 
isn't enough to do the actual recording/encoding and writing to disk.  
This was what the problem was for me.  When using a software card, I 
would get 40-50% usage while just recording.  When I didn't have XV 
working I would get 50-60% usage while playing recorded video.  So on 
liveTV it pegged the proc and I got the stuttering described here.  
Watching a recording only was no problem, as the overly large 50% usage 
was not too much to max out the proc.
Of course, since stopping it for a while and then letting it play solves 
the problem for you, it seems the problem is elsewhere.  Still, maybe a 
good idea to check usage with top while playing back only.  I'd imagine 
with XV enabled you should get well under 10% usage, maybe like 5% or so.
Raphael