[mythtv-users] Can a pcHDTV record standard definition?

Brian Wood beww at beww.org
Wed Dec 13 02:59:58 UTC 2006


On Dec 12, 2006, at 6:09 PM, Brad wrote:

> On Tue, 2006-12-12 at 16:44 -0700, Brian Wood wrote:
>> On Dec 12, 2006, at 3:54 PM, brad at bradandkim.net wrote:
>>
>>>> I don't yet have an HD TV but hope to in the near future.  In the
>>>> meantime, I need another capture card.  If I get a pcHDTV card
>>>> will it
>>>> record standard definition now and allow for the HD upgrade or do
>>>> I need
>>>> to buy a card that will be obsolete for me in the coming year?
>>>>
>>>
>>> I think I answered my own question.  pchdtv.com states that the
>>> HD-5500
>>> supports NTSC.
>>
>> Quite correct, but it supports it only as a "dumb" frame-grabber card
>> - the Video must be compressed/encoded by your CPU.
>>
>> The commonly-used PVR cards have a hardware encoder on the card so
>> their output is an MPEG stream, thus requiring no CPU power to encode
>> the video.
>>
>> So as long as you don't try and use the card for NTSC on a low-
>> powered machine it will work.
>>
>
> Ahhh...that's good to know.  The backend is an AMD 64 with a Gig of  
> RAM
> and has been fine, but I would be adding a tuner and often playback  
> to a
> second frontend as well.  I better be careful about that.


Myth encodes video from a frame-grabber either as RtJPEG or MPEG-4.  
The former takes less CPU to encode but produces larger files.

Playing back MPEG-4 on a F/E takes more CPU than MPEG-2 or RtJPEG.

You can't get any help from XvMC for anything except MPEG-2, so your  
F/E CPU will have to do the decode, so I'd be careful about encoding  
MPEG-4 if you are playing back on a slow F/E.

Not really a "problem" but something to be aware of.


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