[mythtv-users] best quality capture card for software encoding?

Nick knowledgejunkie at gmail.com
Sun Feb 26 00:18:23 UTC 2006


On 25/02/06, Steve Briggs <zzybaloobah at yahoo.com> wrote:
> On 25/02/06, Nick <knowledgejunkie at gmail.com> wrote:
> >
> >What settings are you using (resolution/bitrate)? I'm constantly
> >impressed with my PVR cards (350/150) and their quality output. I'd be
> >very surprised if using a dumb framegrabber and software encoding
> >resulted in higher quality output than using a card engineered
> >specifically for this purpose.
> >
> >Nick
>
> Seems to me a dumb framegrabber and software encoding is "..a card
> [and software] specifically engineered for this purpose."
> The dumb framegrabber was engineered for grabbing frames and
> returning a digital stream & the software was engineered for
> encoding it.

I don't dispute that at all. I spent several years (prior to using
MythTV) using my faithful WinTV-PCI card (BT878) and capturing to
HuffYUV for large lossless-compressed captures when my CPU power
wasn't quite there for realtime encoding. I would use 2-pass TMpegEnc
MPEG-2 encoding or 2-pass DivX encoding on the resulting captures.

I would still be surprised if the quality from a framegrabber using
software encoding i be noticeably better than using a hardware encoder
card, especially when outputting to TV. Couple that with the fact that
you can use multiple PVR cards in a single system with little impact
on system responsiveness or the PCI bus, and then drop the files to
DVD with no re-encoding, and, for my purposes at least, it's a good
sell.

IIRC the PVR-150 series cards have better filtering than the earlier
PVR-250/350 cards, but from my digital cable boxes both cards produce
quality rivalling that of the direct input into the TV.

> Once you get to a digital stream, is MPEG-2 inherently better
> than MPEG-4? And, many users transcode to MPEG-4 anyways to
> save space... so I don't see any possible advantage from MPEG-2.

MPEG-4 should give a smaller filesize for the same video quality, but
I guess the choice of using H/W MPEG-2 or S/W MPEG-4 is dependent on
several factors - CPU power, number of simultaneous streams to
watch/record, whether output to DVD is required, whether drive space
is at a premium or if the user keeps hundreds of hours of video etc.
I'd also venture that more consumer video devices support MPEG-2 than
MPEG-4, but again, that's changing as MPEG-4 becomes more mainstream.

I still encode some material to MPEG-4 after having captured it on a
PVR card - using 2-pass encoding so I can be confident about
filesize/quality etc. I find this material almost indistinguishable
from the MPEG-2 source, especially on a smaller TV. A key aspect of my
using MPEG-2 (aside from wanting to keep CPU usage/heat/noise to a
minimum) is the fact that my DVB cards also output MPEG-2 so I can
easily put material on DVD with the minimum of fuss.

Nick


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