tomlin@hc.dspo.gov (Bob Tomlinson) (05/18/89)
in article <8905042046.AA22765@cs.utexas.edu>, pcinews!observer@cs.utexas.edu says: > My company is looking for some type of device to allow us to capture the > images on a 386i/250 screen and convert them to NTSC (US television) > devices, such as a common video recorder. The following is my opinion from trying out all boxes except the YEM box and the new Lyon-Lamb box (but hearing about them). I am VERY new to video (NTSC is mysterious and bizarre to people from the digital world) so I may have some of the following incorrect. If so, please forgive me and correct me. Also, note that this is a FAST moving technology right now. My comments are likely to be obsolete at SigGraph and certain to be obsolete by the next NCGA and NAB. Most of the boxes are also available in PAL versions for people outside the US. The following are the companies that make such boxes (in aproximate order of perceived quality. Note that cost and quality don't necessarily coorelate.): Lyon-Lamb California: (818) 843-4831 or New Jersey: (201) 530-0501 Photron Distributed by Electro Communication Systems, Inc (214) 358-5195 RGB Technologies (415) 848-0180 YEM (Yamashita Engineering Manufacture) Distributed by Grunder and Associates phone number ??? Folsom Research, Inc. (916) 983-7236 Actually, I think you can get several of the different boxes from Electro Communications Systems (see their number under Photron above). We found them to be VERY knowledgeable, helpful, and friendly. The Folsom, YEM, and RGB Technologies box all take the entire screen and convert the greater resolution of the Sun or other workstation to the lesser resolution of NTSC. You necessarily loose resolution. Of these the RGB Technologies box looks best. The RGB Technologies box does one thing that none of the other boxes do (not even the Photron and Lyon-Lamb boxes): it can merge a NTSC video source with the hi-res source and put the merged video on its NTSC output. We haven't figured out a real utility for this feature for our applications, but it's neat. Possibly you can use it in place of a digital effects box if you only need chroma key (put a picture of someone in the corner to talk about what's being displayed). Lyon-Lamb and Photron have a couple boxes out. The new Lyon-Lamb is the box I'm refering to (the one introduced at NAB). The old one didn't operate at full video rates (30 frames per second). The new Photron box I'm refering to has "EZ" appended to the part number (the old one did line dropping instead of line averaging). These are also just out (only a couple boxes are in the US). The boxes by Lyon-Lamb and Photron can do what the first set of boxes do (except for RGB Technologies video mixing) and can also capture a smaller NTSC size window at full resolution. This allows you to see a portion of your screen without any loss of resolution. Lyon-Lamb/Photron differences: - The Lyon-Lamb box comes standard with an RS-232 input to the box to control operating parameters (amount of smoothing, partial screen/full screen mode, what portion of the screen to capture when in partial screen mode, etc). The Photron box doesn't have that standard although I understand it can be added; apparently they dropped it because it wasn't used on older boxes (although it's important to us). - The Lyon-Lamb box has adaptive circuitry to adapt to adapt to different hi-res monitors (see below for a description of this). - The Lyon-Lamb box can take as input not only a NTSC resolution sized window on the workstation, but can also tak an arbitrary sized window (whatever aspect ratio) and do a reasonable job at putting it into a NTSC signal. I've not seen this, but it sounds really neat. - The Lyon-Lamb box is said to do a better job (better quality) to others who have seen both it and the Photron box. - The Lyon-Lamb costs less than the Photron box. Features/Things to be careful of: - Be careful for boxes that simply drop lines instead of doing averaging/smoothing. Otherwise if you have a one pixel wide line on a raster scan that is to be dropped it will be gone on the NTSC. - Can you control the amount of smoothing? Hi-res monitors are usually ~60KHz monitors. NTSC video is 30KHz. Therefore these boxes draw alternating horizontal traces down the screen (interlaced). If you have a black horizontal line and then a white horizontal line these will be drawn at alternating times. You will therefore see a beating between the two lines. This can be negated by smoothing (averaging neighbor pixels with a drawn pixel). The more smoothing means less beating, however smoothing fuzzs the lines (or characters) making things less clear. - Is the internal encoder a quality encoder or do you need an external encoder? An external Farujda (sp?) encoder (high quality) is ~$8K by itself. - When seeing a demo, is it going to a normal monitor or is it going to a SVHS (Super VHS) monitor (more scan lines)? Does the box have an SVHS out? - How do you change from monitor type to monitor type (Sun to uVAX, etc)? Some have adaptive circuitry. Some you must change a crystal. How hard is it to change the crystal? I have heard claims that the adaptive circuitry is less reliable and gives you a lower quality image (although I haven't examined that). - Bob Tomlinson tomlin@hc.dspo.gov Bob Tomlinson -- tomlin@hc.dspo.gov -- (505) 667-8495 Los Alamos National Laboratory -- MEE-10/Data Systems