[mythtv-users] Re: Slow Channel Change

Jarod C. Wilson jcw at wilsonet.com
Thu Aug 7 02:05:53 EDT 2003


On Wednesday, Mike Foley wrote:

> First off, let me preface this with the fact that I am new to Linux / 
> Unix, so pardon my ignorance.  With that said, I would like to thank 
> Jarod C. Wilson for his excellent install guide at 
> http://pvrhw.goldfish.org/tiki-page.php?pageName=rh9pvr250.  The step 
> by step details helped immensely.  I am running MythTV on a Athalon 
> 1700+, with 512 Mb of DDR ram, a 60 GB hard drive (DMA is turned on), 
> the video card is the nVidia 440Mx, and of course I am using the PVR 
> 250 capture card.  Also, I am using the sVideo input to the capture 
> card as I have satellite service.  Although I haven’t built the IR 
> transmitter yet to actually do the channel changing (I created a dummy 
> channel.pl script so that Myth thinks it is changing the channel), 
> every time I change the channel, the screen freezes and I have to wait 
> about 3 seconds for the OSD to display the new channel info and the 
> video to resume.  Other than not using the tuner input, the only other 
> area where I deviated from Jerod’s guide was on the audio setup.  For 
> me, OSS worked so I skipped the steps for ASLA, for the most part the 
> audio is fine with OSS, occasionally I will get a stutter affect (I 
> like to think of it as the Max Headrom affect).
>
> Please let me know if there is anything else I can try to reduce this 
> time, or is it normal, and if so can I suggest that you follow what 
> dish network does which is to change the new channel’s info while the 
> video is being buffered.

I think what you're seeing is normal. While you're watching "Live TV", 
you're not actually watching live TV. You're watching a video stream 
that is buffered a few seconds, so you can do things like pause and 
rewind. The system needs a bit of time to get some video to disk before 
it starts spitting it out to the screen, and has to start a new capture 
every time you change channels, so there'll definitely be a bit of a 
pause on channel change.

As far as the audio stutter, I get a bit of that when changing channels 
also (that I didn't w/0.9). I believe Isaac put a fix into CVS 
recently, but the RPMs from ATrpms are version .10, prior to the fix. 
There are a few people out there building their own RPMs from CVS 
source (I haven't had the time to play with this myself yet), but if I 
recall right, Isaac said .11 should be out soon (with the fix 
incorporated), at which time Axel will update his RPMs, and you'll be 
able to just update to those with apt. Perhaps the guide should 
incorporate some info on updating your system, too...

As far as updating the OSD info prior to video resuming on channel 
change, the usual response is "submit a patch!" But not a bad 
suggestion. (I'm no programmer myself; I'd love to do some coding if I 
thought I wouldn't screw it up tremendously).
-- 
Jarod C. Wilson, RHCE
<jcw at wilsonet.com>
"A wise man once said nothing at all."



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