[mpeg2] Re: Recommended capture cards?

[Lawrence Gold <gold@shell.aros.net>]

On Sun, May 27, 2001 at 03:59:02AM -0600, Warren Young wrote:
> 
> I have yet to see a cheap capture board with good color support.  They
> tend to have a poor D-range, forcing you to either destroy the white
> detail to get good blacks and good contrast, or to accept low contrast
> in order to have detail in both the dark and the light areas.
> 
> This is probably not the fault of the BT8x8 chip, though, because some
> of the most highly-regarded Bt8x8 capture boards -- Osprey's boards -- 
> are based on these chips.  But, instead of paying $50 (like for the
> WinTV Go) you pay $170+.  Most of their boards do work in Linux, FWIW. 
> http://www.viewcast.com/viewcast.html

Okay, I'll just raise my definition of "cheap" to the $170 range then.
;-)

> At that bitrate you'd better be using SVCD frame sizes as well.  For
> 640x480 or full D1, I personally never go below 3 Mbit/s, and I only go
> that low with a good encoder.  Visit the link in my signature for my
> reviews of 10 different MPEG hardware and software encoders (not yet
> including sampeg or bbmpeg, unfortunately).  Notice how poorly most of
> them fare at 3 Mbit/s with challenging video.

I'm using 480x480, which is the "standard" SVCD size as far as I can tell.

> Inserting I-frames won't fix blockiness or artifacting.  In fact, it
> will worsen the problem, because they take more space than P or B
> frames.  Quite the opposite, you may find that increasing your GOP
> length will help more.  As long as you do that with an encoder that can
> close the GOP early and start a new one when necessary, there should be
> no major problems using long GOPs.  Unfortunately, most encoders are
> limited to 15-frame GOPs.

Interesting, I'll give this a try.  The last time I tried to adjust the
GOP length, my machine rebooted the moment I tried to install the kfir
driver.  I don't remember what value I had set it to, though.

Thanks for the info.