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Marc Barrett's Rantings

Marc Barrett's Rantings

Post by Dale Ada » Mon, 11 Oct 1993 05:27:10






>  DA> You can always digitize the
>  DA> video, scan rate convert it, and show it on a display at another
>  DA> resolution/frequency (which is what the AV Macs would do in this
>  DA> situation).

> Hmmm... Wouldn't it be slightly difficult to grab video when you can't
> view what you grab until *after* you've grabbed it?

This isn't the case with the AV Macs.  The digitized video data stream is
sent to a separate pixel data port on the RAM/DAC where it is mixed with
the computer generated graphics.  Thus, the video being grabbed is visible
on the display at all times.

Quote:>  DA> Full screen
>  DA> video  can be shown at the full frame rate of the incoming video -
>  DA> 60/50
>  DA> fields/sec for NTSC/PAL video.  Note that with only 1 MB of video RAM,

> But not on a SVGA monitor, right? You'd need a multisync, right?
> (BTW - does Apple sell any multisyncs?)

No, Apple doesn't sell any multisync displays.  However, you don't need a
multisync monitor for this, as the digitized video can be seen on any
display supported by the machine (from NTSC on up to 1152x870 75 Hz
noninterlaced).  There are some tradeoffs on the size and pixel depth of
the video window and the display size/pixel depth and amount of available
VRAM.

Quote:>  DA> (I believe I've  heard numbers on the order of 15 fps or so for a
>  DA> 320x240 window.)  You  really need hardware compression to make this

> 15fps for 320*240? But that's sustained, not just a short burst to RAM?

I think so, but I could be remembering incorrectly.  If you do the math,
that's a bit over a 2 MB/sec. data transfer rate.  You would need a fairly
fast hard disk to support a this on a sustained basis, but they do exist
and are available on the AV machines.   There's probably some sort of
software compresssion being used to reduce the data rate (although that is
just speculation by me as I don't have a Q840av readily available for
test).

Quote:>  DA> feasible.  The AV Macs allow  the easy addition of hardware compression
>  DA> by providing a slot for access  to the digital video pixel data stream.

> What kind of compression is available for the AVs? MPEG?

Good question.   To the best of my knowledge there aren't any currently
available hardware compression cards which use this slot.  I have seen
MPEG demonstrated (so I know it's certainly possible to produce an MPEG
hardware compression card), but I don't believe anyone actually sells this
yet.   Certainly all of the QuickTime software codecs are available, but
that's a far cry from what's possible with hardware compression.

- Dale Adams

 
 
 
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1. Marc Barrett's Rantings

     Having lurked for a three-month haitus (test of supreme will-power)
I return to find nothing has changed. MB is now ranting about the latest
new Mac to hit the marketplace. It seems to me that Apple has released
a new machine at the rate of about one a month and are as rapidly
orphaning those that have come before. Witness the Quadra line and
keep a scorecard. 8-)
     Now MB is also sounding off about voice recognition. A serious
question for you Marc...Do you think their speech-recognition will
be as good as the hand-writing recognition in the Newton? And why
hasn't MB been just raving on and on about the Newton? It is the
greatest thing since sliced bread, isn't it Marc? The truth is the
Newton doesn't work...plain and simple. Read any article by anyone
who has used it. How long should it take to train it?? Two weeks
isn't long enough, and if I own something I can't use for two weeks,
what good is it?
     IMHO, John Sculley and his upper management sucked the life-blood
out of the company, damn near ruining it, while in the process making
themselves extremely wealthy. Latest stock price is $24.50 a far cry
from the $60-$70 dollar range just a few months ago. Have any response
for this? After the latest round of layoffs, they canned almost every
program that set the company apart as revolutionary and a great place
to work. Why don't you ever mention this about your beloved company?
     Tell me Marc, what is it that Apple has that I can't get on a clone
for less. What one software product (or hardware product) for that matter
sets it apart? Because they are heading, slowly but surely, into being
a niche machine. I wonder how long before we see Apple doing a games
console. 8-) At least the Amiga has the VideoToaster, but what does
set the Apple line apart other than inflated hardware and more importantly
software prices. Not a thing.
     So the next time you want to come and spout off, exercise some
self-control and try not to post. It might even do wonders for
your social life.

                             Thorne K. Kontos
                             Resident chairperson of the
                             Curtailment of Personal Liberties Committee

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