[mythtv-users] XvMC, Plextor Question, and Sound

Brian Wood beww at beww.org
Fri Feb 10 22:24:30 UTC 2006

On Feb 10, 2006, at 2:12 PM, Jesse Guardiani wrote:

> Brian Wood wrote:
>> So, do I understand this correctly:
>> I've installed a Plextor ConvertX (I've run out of PCI slots).
>> Even if I am ultimately successful in getting XvMC to work, I would
>> get no help from it in playing video from the Plextor (live or
>> recorded) as it is MPEG-4???
> I think that is currently correct, yes. I believe some unichrome
> hardware is capable of mpeg-4
> XvMC acceleration, but I don't think any drivers/libraries support  
> that
> functionality yet.
>> Is there any work afoot to support Plextor modes other than MPEG-4?
> Not that I'm aware of. However, I'm interested in doing just that once
> 0.19 is released. I
> have a plextor, and like you I'm out of PCI slots, so the Plextor is
> really my only option if
> I want a second tuner.

Wow, you *are* short of slots. My Plextor was to get a fourth capture  
card :-)

> In addition to XvMC support, recording to Mpeg-2
> would allow
> for DVD burning via MythBurn.

Well the world is going the other way, towards mpeg4. I heard that  
DirectV's newest satellite is putting out mpeg4 streams, with  
Echostar to follow soon.

Well you could always transcode mpeg4 to mpeg2 and then burn, would  
take a lot of CPU cycles though. In fact you'd have to transcode  
anyway, as the Plextor only supports 640x480, unless you recorded at  

> Maybe I'm being naive, but I don't think it will be all that difficult
> to add support for mpeg-2.
>> The Plextor has been working surprisingly well, but if anyone is
>> considering one, be aware that it does not embed the sound in the
>> MPEG stream, the way a PVR does. Rather it sends uncompressed sound
>> to ALSA as PCM, which requires a sound card input.
> MythTV then compresses this audio to mp3 using your system's CPU (by
> default - you can
> turn it off in the recording profiles), so the plextor will actually
> cause mythbackend to burn a
> good bit more CPU than a true PVR card.

That's my point, and I wonder why Plextor went the way they did.  
AFAIK there are no MPEG2 encoder chips that won't do audio, so  
there's no money to be saved there.

>> I guess I could replace two of my 150s with a 500, freeing up a slot
>> for a sound card, but I think I'll wait 'till the 500 support settles
>> down a bit.
> 500's seem a bit more picky about their drivers, PCI slots, and inputs
> than other IVTV cards
> too.

The biggest problem I'm aware of is the "new" tuner modules, but  
Hauppauge has always changed tuners as often as Microsoft changes  
APIs, but it is an attractive way to save slots.

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