smart@manta.mel.dit.csiro.au (Robert Smart) (06/06/91)
Apple's recent announcement described compression rates for video of 5-25:1. I'm surprised you can't do better. I'd like to understand the problem better: 1. What is the typical form of uncompressed video data? E.g. is it a series of rectangular arrays of rgb triplets with each colour in the range 0-255? 2. What sort of rates of edge movement do you see in video data: 2 pixels per frame; 1 pixel every 2 frames; or what? I realise this varies a lot but I'm thinking of an average TV program. 3. Is there any example video data in digitized form one can easily obtain (e.g. by ftp)? Bob Smart <smart@mel.dit.csiro.au>
d88-jwa@byse.nada.kth.se (Jon W{tte) (06/07/91)
> smart@manta.mel.dit.csiro.au (Robert Smart) writes:
Apple's recent announcement described compression rates for video of
5-25:1. I'm surprised you can't do better. I'd like to understand
the problem better:
Think again: this was REAL TIME even on LOWEND macs (like the LC)
1. What is the typical form of uncompressed video data? E.g. is it a
series of rectangular arrays of rgb triplets with each colour in
the range 0-255?
Pretty much correct - it's close, and it's called a 24bit Direct PixMap.
2. What sort of rates of edge movement do you see in video data: 2 pixels
per frame; 1 pixel every 2 frames; or what? I realise this varies a
lot but I'm thinking of an average TV program.
You see a lot more motion than that. Think about it: at a rate of 15-20
pictures per second (about what QuickTime presently manages) over, say,
200 pixels, a motion over the screen would take 10 seconds at an 1 pixel
per frame motion rate. Not to mention scrolling/panning/zooming, and the
noise and color/shadowing variations in real-life video.
3. Is there any example video data in digitized form one can easily
obtain (e.g. by ftp)?
Well, Apple has seeded some developers with an Alpha release
that contains some QuickTime movies - already compressed.
Else I know of nothing, but it surely exists (?)
--
Jon W{tte
h+@nada.kth.se
- Speed !