wayne@dsndata.UUCP (Wayne Schlitt) (05/28/88)
I know that this probably a frequently asked question but...
I need information on how we can capture RGB output on a 8mm, VHS or
Beta tape.
We would like to put together a demo/training tape and we have tried
taping right off the screen, but we have not been satisfied with the
results. (the characters are not _quite_ readable...) We are using
Hewlett Packard series 9000/300 computers so any special cards are
probably out. We are using low resolution graphics (512x380) so I
am not concerned about the resulting resolution as long as the
characters are legible.
So, if you have any info on if this can be done, who's hardware to use
or where I can get more information please mail me a message.
Thanks much,
Wayne Schlitt
| Design Data Corporation
uunet!hpda!hpfcla ------\ | 1033 "O" St. Suite 324
decuac!super!eecae!upba +---> !dsndata!wayne | Lincoln Ne, 68508
ihnp4!upba -------------/ | (402) 476-8278jpdres10@usl-pc.UUCP (Green Eric Lee) (06/10/88)
In message <126@dsndata.UUCP>, wayne@dsndata.UUCP (Wayne Schlitt) says: >I need information on how we can capture RGB output on a 8mm, VHS or >Beta tape. > > >We would like to put together a demo/training tape and we have tried >taping right off the screen, but we have not been satisfied with the >results. (the characters are not _quite_ readable...) We are using >Hewlett Packard series 9000/300 computers so any special cards are >probably out. As for legibility of characters: in general, for the resolution you mention, 9x7-pixel characters are out of the question under the NTSC color standard used by VCR's etc. You'll need to double the character size. The problems are limited video bandwidth, and interlace flicker. These problems will also require you to dither the edges of the characters for best results, so that there is a low contrast between subsequent pixels on the screen (which also reduces the bandwidth requirement horizontally). Most cheap television station character generators still don't do this, which is why your picture hashes over and an annoying buzz comes out of your speaker when they scroll their flash-flood-warning or whatever along the bottom of your television screen. Which is also why a number of TV stations are junking their old character-generators in favor of Amigas -- with a simple $300 genlock and a $1,000 computer, they can replace cranky old equipment that costed $10K only a few years ago. In any event, small characters will always be "almost readable" when displayed with a NTSC-standard device, because of the limited bandwidth. Once you solve the character-size problem, what you need is an RGB-to-composite converter, and then feed the output of the converter to the VCR. The only reference I have right now is for the Amiga computer, so I'm afraid that I can't really help you with your HP. Still, I took the cable apart, and it's a single chip on a tiny PC board, so obviously it's a one-chip solution from someone out there. (but the cable is wired for the Amiga's RGB-analog output, not for whatever the HP has, so it's useless for your purposes). Note that the resolution you mention (512x380) is not compatible with the NTSC standard used by VCR's etc, unless it's a 60-frames-per-second interlaced display (two 30-frames-per-second fields offset by one scan line -- i.e., the NTSC standard). So a simple RGB-to-composite conversion might not be adequate. You'd need a frame-rate-converter of some kind, which I understand is a quite complicated and expensive piece of equipment (note the bi-annual postings on the video newsgroup about converting 50-frames-per-second European videotapes to 60-frames-per-second American videotapes). There is also a device called the "Polaroid Pallette" which will produce color slides from various video formats. About $2K, I believe, and you don't want slides, you want video. But if you can't get video out of your computer, you might end up having to take photographs of your screen (another subject altogether), and then feeding the slides 1-at-a-time into your video camera (there's an attachment for video cameras which, in conjunction with a light-table, assures that you get a consistent light source and decent results). I'm not at work, so I can't give you any brand names or anything. Just look in any reputable video or photography magazine for such supplies. -- Eric Green elg@usl.CSNET P.O. Box 92191, Lafayette, LA 70509 ut-sally!usl!elg uunet!nuchat!elg "Is a dream a lie that don't come true, or is it something worse?"