Date: 17 Nov 1996 22:22:12 -0800 From: pete@news.interworld.net (Peter Carah) To: freebsd-isp@freebsd.org Subject: Re: bang bang bang bang - lame lame lame lame Message-ID: <56ovak$9i8@news.interworld.net> References: <7574.847917312@time.cdrom.com>
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In article <7574.847917312@time.cdrom.com>, Jordan K. Hubbard <jkh@time.cdrom.com> wrote: > >Standard PAL resolution - we're not talking HDTV here, simply a way of >playing movies from a CD on your TV (and CDs take up much less >space than VHS tape, are more robust, don't stretch or get eaten >by your neighbor's mutant Croatian VCR, etc etc etc.). >I think the thing that's really blocked this technology from taking >off in the home consumer market is the fact that most movies require >two CDs, and fat, lazy american consumers don't like having to get up >in the middle of the movie and swap CDs. Now that the high density >CDs are coming in (Walnut Creek CDROM is getting some of the first >writers for them, in fact) this could change significantly and I could >easily see the entire "I Claudius" PBS special fitting onto a single >4GB CDROM. :-) 4.5 per layer, up to 4 layers... Mastering is tricky, too... Most lazy american consumers I know like EP-mode VHS (or don't know better?) Decent rate MPEG requires more than 2 cds per movie; the fairly slow rate that we used to encode ppv at was about 1/2 gig per 20 minutes. DVD should help this a bunch... >> The last I heard, most "real time MPEG" stuff worked at standard TV >> resolutions (or only mildly better) and was pricey as all heck. > >Not pricey at all, actually. You can buy MPEG decoder boards for >around $200 now, though be careful to avoid the "Real Magic" MPEG >video cards as they are complete and utter crap. I was so disgusted >with mine, not to mention their deceptive advertising practices >(nowhere do they note that the card will work with *one* and only >*one* brand of CDROM - it takes a call to their tech support >department and several hours on hold to learn that tidbit), that I >simply threw mine in the trash. Wish I'd saved it though - I'd have >taken it to the new rifle range I found which allows you to set up >your own types of targets just so long as you clean up after >yourself. :-) Most of the mpeg decoder boards for computer use, and many for TV use, only work at quarter res. You need to be careful, but it still looks pretty good... CDI uses approx a 1mbit/sec encoding at quarter res. >Thankfully, there are other cards on the market now. >> Since computational time should be proportional to the resolution of the >> display, it should be much easier to do a 320 * 200 display (64000 pixels, >> and at 16 bit depth that's 128Kbytes of data) as opposed to a 1024 * 768 >> display (786432 pixels, and at 24 bit depth that's 2.4Mbytes of data). Color depth is not handled the same way in video; depths are 18, 24 or 30 bits but the color is normally subsampled by a factor of 2 and sent as differences; this turns 24-bit depth into 16 transmitted bits; the color resolution is that of 24-bits but with a lower spacial frequency response. I've not seen 18-bit depth used in component digital; 6-bit samples used to be used in sampled composite recording but I think that is mostly gone now too in favor of 8 or 10 bit samples. (and most digital TV recording nowadays is component anyhow.) >Well, PAL is somewhat higher than this and while the frame rate of my >CD-I is unknown, there's no perceivable flicker and I'm pretty >sensitive to video refresh rates below 25FPS. Current PPV (and CDI) use 320x240, or 320x312, or 352x240 or 352x312, depending on the input system and whether NTSC or PAL... (320 from analog sources and 352 from digital; 240 for NTSC and 312 for PAL...) CDI is VERY slow mpeg (around 1mbit/sec). Since mpeg (for movies, anyhow) works in frames you won't see any flicker in the reconstruction (the pixel doubling guarantees no field-flicker). MPEG artifacts usually show up as visible contouring on 16-pixel square boundaries and generally not as motion artifacts. Cheaper decoders use less bits, which makes this effect more visible. Most of the commercial encoders use either 8 or 10 bit component samples. -- Pete
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