[mythtv-users] Capture device for S-video

Rod Smith mythtv at rodsbooks.com
Fri Nov 16 00:09:01 UTC 2007

On Thursday 15 November 2007 17:58:39 Taco Mel wrote:
> I recently switched from analog cable to satellite and
> I am having ongoing audio quality issues with my
> Hauppauge PVR-500 tuner (currently fed by 2 S-video
> inputs from 2 boxes).  Even with the workaround in the
> wiki, and even with my update to that workaround,
> still result in about 1 in 10 of my recordings having
> the "tinny" audio sounds.

I don't own a PVR-500 and so can't offer specific advice on this problem. I do 
have some comments on some of your proposed solutions, though....

> 2. Plextor USB hardware encoder.  The con is that $150
> times 3 is a lot of money.

There's also the Hauppauge WinTV PVR-USB2. The cost is similar, and the device 
produces MPEG-2 video files, which might or might not be preferable to the 
MPEG-4 produced by the Plextor device, depending on your needs. The PVR-USB2 
has some limitations in MythTV, such as an inability for MythTV to control 
the recording bitrate (at least as of 0.20.2; I've not checked the latest 
development versions). The wiki entry goes into some detail on this. I've got 
one and I do use the S-video input, but only for recording from my laserdisc 
player. I recall getting distorted audio on one recording from this source, 
so it's conceivable it has problems similar to those you're experiencing; 
however, I've done dozens of recordings from S-video, so the frequency of 
this problem is far less than 1 in 10, at least in my experience.

There are also some other non-Hauppauge PCI cards. I've got an AVerMedia 
AVerTV M150-D, for instance. I'm reluctant to recommend this card as 
an "everyday use" card; it's just got too many quirks. (See the wiki entry 
for details.) You might be able to find something else that'd be more 
reliable, though.

> 3. Software encoders.  I've got enough horsepower in
> the backend (core 2 duo @ 2.66 GHz) to consider
> software encoding.

I'd recommend against this. I've got a 3GHz Celeron-D, and although software 
encoding works reasonably well when the system's doing nothing else, I get 
dropped frames and audio sync problems whenever the CPU load rises above 
trivial levels. These problems increase in severity with CPU load; they're 
pretty minor with low CPU load (say, playing back one stream while recording 
another), but they can get very annoying if the system is pushed very hard 
(say, transcoding while recording). Having a dual-core CPU would probably 
help with this a lot, but I suspect you'll still run into problems from time 
to time, particularly if you want to record two channels while watching 
another. Also, I'm not really 100% sure that the problems are related to CPU 
load per se; it could be bus load that's causing the problems, and I wouldn't 
expect a dual-core CPU to help much with that. Overall, I'm much happier with 
my MPEG-2 encoders than I was using software encoding.

> 4. Output the signal from the boxes on RF and then
> capture that as analog which I would guess might work
> since I never had the "tinny" audio problem in 3+
> months of recording analog cable.  Con is the
> degradation in the signal quality.

You might want to consider reconfiguring one of your tuners to work in this 
way as a test. You could then do a side-by-side comparison to see just how 
much degradation you'll have in quality, and judge whether that's acceptable.

Rod Smith

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