Mailing List Archive: Slow Channel Change

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.

Thanks,
Mike

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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@wilsonet.com>
"A wise man once said nothing at all."

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