wmartin@brl-smoke.ARPA (Will Martin ) (02/21/86)
This query was inspired by a message on the ARPA "Videotech" mailing list with the subject of "Picture-in-a-picture", and posted originally to that list. I'm posting a revised version here: How do the sets which advertise "picture-within-a-picture" or have the capacity to display multiple pictures do it? How do they display 525 lines in just part of the screen area? I thought that NTSC TV's only had enough phosphor dots on the screen to support the standard number of lines, so that putting a subsidiary picture in the lower corner, for example, means scrunching that channel's display into just part of the available screen display space. Do they discard lines, and only show some fraction of the 525? (Or whatever is the real number of displayed lines, not counting those in the Vertical Blanking Interval?) Also, what sort of flexibility is available these days in such sets? Let me describe what I want and you video experts out there can tell me how soon I can expect to see it, if at all: Lets take the example of watching network news. Around here, all three networks' national newscasts are on at the same time. I want to see *all* of them, paying attention to particular items in first one and then the other. I do this now by flicking constantly between channels, but doing this causes me to miss something I would want to see on a different channel, because it has begun after I had started watching some item on another channel. What I need, of course, is a TV that will let me quarter the screen, displaying each channel in one quarter (I'll put some local independent in the fourth quadrant or leave it blank). The first objection that comes to mind here, of course, is the sound. I can't have all three sounding at once, but I want to know what they are saying. So, I would like separate closed-caption decoders available for each, so I could see the words displayed on each channel's image, and, with a remote control, call up the actual audio for that channel I am paying closest attention to at that time. At other times, I would often want to watch the video from two programs at once, but have the audio from only one, and be able to switch between which input video is feeding the "main", or largest & clearest, image and which is driving the subsidiary display, again by remote control. (That is, be able to toggle back and forth, with channel "a" being displayed in the main picture, and channel "b" in the other, and then flip it so that "b" is in the main, and "a" is in the secondary, with a single control command, but not have the audio change during this flip-over.) So, is this possible? I can see that it would require the TV to have at least four tuners (to feed four different channels to a quartered screen simultneously); probably four separate closed-caption decoder circuits; and a pretty elaborate programmable remote control. This is just electronics, and therefore relatively cheap. What about the display? Would some new form of picture tube be required to support this, with multiple built-in guns for each separate input possible, or would some sort of "multiplexing" of the display-driving circuit let this work in a sort-of-standard CRT? What is now available that could begin to approach this? Is anyone working on such a device? Or should I just build three or four separate TVs into a single cabinet and feed their audio to a remote-controllable sound system? Will Martin ARPA/MILNET: wmartin@almsa-1.ARPA USENET: seismo!brl-bmd!wmartin