[mythtv-users] please explain XvMC

Chris Wieringa cwieri39 at calvin.edu
Mon Apr 19 09:13:45 EDT 2004


>Chris Wieringa wrote:
>> Yep, X video Motion Compensation is a feature that can be enabled on some
>> cards (Nvidia mainly, but some ATI cards have support for it AFAIK) to do
MPEG2
>> decoding.  Usually this is used with playing DVDs, however, the Hauppauge
>> PVR-x50 cards capture streams in MPEG2.  Therefore, decoding of these
streams
>> are done on the video card with little impact on the CPU.  If you are using
a
>> an analog bttv capture card, you will not be capturing your streams in
MPEG2,
>> so there is no point in compiling in XvMC.
>> 
>
>I thought the PVR-x50's do their own decoding, so their wouldn't be any 
>need for the video card to do any decoding.

The PVR-350 has both an encoder and decoder (and TV-out), while the 250 has
only the encoder.  If you had a 350 and you wanted to do TV-out on a video card
you could still use XvMC to achieve hardware decoding.  However, at that point
you might at well just have gotten a 250 and saved yourself some money.  

Chris Wieringa
cwieri39 at calvin.edu


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