Messages in this thread | | | From | "Khimenko Victor" <> | Date | Fri, 18 Sep 1998 00:21:35 +0400 (MSD) | Subject | Re: VHS backups - that's why I'll keep Windows98 on my comp |
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16-Sep-98 16:18 you wrote: > On Tue, 15 Sep 1998 03:05:26 -0500 (CDT), Oliver Xymoron said: >> The spec I gave - 320x200x8 at 15 frames per second - is the resolution of >> an old Fisher-Price video recorder that recorded on audio tapes. NTSC >> resolution is nominally ~640x~484x~18bpp(1) at 30 frames per second so my >> original estimate was allowing for more than a 16x degradation in quality, >> or looked at another way 16:1 ECC. VHS is bad, but not so bad that that >> wouldn't work.
> You get a horizontal resolution of about 250-300 in the luma signal when you > record on VHS. The chroma signal is much worse and isn't worth bothering > with. To put it another way, the bandwidth of the VHS luma signal is about > 2.5 MHz so base your figures on that. However, whatever encoding you use > will obviously have to include the correct horizontal and vertical sync > signals to avoid confusing the recorder and you will want to avoid the > head-switching noise which generally occurs during vertical retrace.
> However, I have a feeling that some of the processing used in VCRs has > the effect of merging adjacent lines somewhat, so you might want to > trust only every alternate line.
In fact backup on VCR is the only reason why I'll keep Windows98 on my comp for a very long time. There are drivers for DOS, Windows95/98 & Windows NT 4.0, but not for Linux and I'm not powerfull enough to write my own... Anyway it's really cheap: 350Kbytes/sec (PAL/SECAM VCR's only, not NTSC ones) and on 4hr VHS you could store 4.8Gb of data (with huge amount of error-correction code of course so raw data stored on VHS is >10Gb). Sometimes cheap chineese VHS reauires 2-3 tries (performed automatically by this horrible Arwin) to read information but for last two years and 20+ VHS's seen by me there are was no data loss...
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