Apple Clones (was: [rescue] BMRT SGI)
Joshua D Boyd
jdboyd at cs.millersville.edu
Thu Dec 19 11:02:04 CST 2002
On Thu, Dec 19, 2002 at 11:07:53AM -0500, Kevin Loch wrote:
> Joshua D Boyd wrote:
> So, DigiBeta is
> >certainly better, but also far more expensive.
> DVCam, MiniDV and even D8 all use the exact same
> bitstream, just different physical media (so I read).
> Is DigiBeta different?
Here is my understanding of these devices.
DVCAM and DVCPRO use 4:1:1 sampling, along with MiniDV and Digital8.
These all use the DV format which is MJPEG based to muy understanding.
These devices tend to communicate via firewire and composite or SVideo
(Y/C). I think they all have 480 lines of vertical resolution, but maybe
they offer a variety of options. I'm not positive on that point. The
480 is significant because NTSC calls for 483 or 486. However, it's no
big deal because it is trivial to just add a few black lines.
Digital-S (from JVC), DVCPRO-50 (from Panasonic), Digital Betacam, D-1
and D-5 all use 4:2:2 sampling. I think each one chooses for itself
what compression scheme to use. These devices tend to communicate by
SDI and component.
Of course, the real tests for quality are how good the video looks. A
good DV codec makes a world of difference. This is one place where the
capture card comes in. Some firewire cards include the codec on the
card. My impression was that this is inferior to a software codec, but
at the time the speed boost could mean a lot (early P2 days when PPros
were still common), that may be outdated info now. If it isn't, then
why would people continue to buy expensive firewire cards made just for
However, perhaps my biggest complaint was that digital was supposed to
get rid of generational loss. But when you start using JPEG
compression, you introduce it again everytime the video is compressed
and decompressed. Argh! This is one reason why non-destractive editing
is so needed, although it was always convienient.
In this day and age, why can't people just through a few 100 gig IDE
drives into their machine on a good IDE accelerator and work
uncompressed? Or, hand them off an IDE->SCSI raid (yeah, I know, they
seem to be quite expensive for some reason).
Joshua D. Boyd
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