Author: Shalroth (wwwcache-b.lmu.ac.uk)
Date: 02-11-2002 13:08
Not only is the videostream compressed, it's encrypted too using a scheme called CSS. The decryption is handled by the application software - this is why if you try to copy a VOB (Video OBject) to a hard disc on a PC/Mac it really struggles (actually, a Mac can do it, but it won't be able to do anything with the file afterwards. A PC just sits there saying 24153672 minutes remaining or something stupid while the error correction code tries to correct the encrypted data...sheesh)
The host machine needs to be silly fast to decode MPEG2 in realtime. My 400MHz iMac can do it, but the interactive menus are damn slow. You need a 500MHz PC to do it effectively too. And bear in mind that decryption is slow as well.
Even if the video weren't compressed, well, you could only fit about 15 minutes of video on a disc, but the amount of bandwidth required would be silly. The amount of pixels is too high for an ST screen, a Falcon or expanded TT could cope but they couldn't receive the uncompressed video stream quickly enough (bus bottleneck).
You could preprocess the video though, like with AniPlayer. My TT isn't fast enough to playback MP3 in realtime (does a darn sight better than a 32MHz (I mean 33 really) 486 can) but I can decode to AVR format at an acceptable speed and playback afterwards. But for display on an ST, I'd need to downsample to 320x200x16, non-compressed, something like a cyberpaint SEQ or AutoDesk animator FLI file. That would fit comfortably on a DVD even without compression.
And then we find out...STs can use DVD drives. SCSI DVD drives are a little more expensive (OK, a lot) but any computer capable of using CD-ROM protocols can use DVDs (33MHz 486, using MSCDEX 2.1 can anyways). Then we think...if we're going to the trouble of converting from DVD MPEG2 to FLI, we might as well do it at the start, and just write an FLI file to the DVD and let the ST play it from there!
I've had a DVD-ROM attached to my TT (briefly) and although it was completely pointless I could browse a PC disc with shareware on.
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