parkin (12/15/82)
I have begun looking at VCRs and noticed that the top-of-the-line VHS models can record/playback audio in stereo, usually with Dolby noise reduction. Apparently prerecored movies with stereo audio are also showing up. Does anyone out there have one of these stereo recorders? Is it worth it? Have you played any stereo prerecorded movies? Do they sound okay? I listened to a couple of models in a dealer's showroom: a Hitachi and a JVC. The Hitachi didn't have Dolby and it sounded no better than an am radio (except it was stereo). The JVC had Dolby and sounded much better (though not audio cassette quality), however the JVC (I don't remember the model number) could not record the video from its tuner and audio from an auxillary input simultaneously, which means it can't record simulcasts. I understand that Panasonic's top model can record this way and has Dolby, but I haven't listened to it yet (most dealers don't have theirs connected to a stereo system). One last question: does anybody out there know anything about Beta Hi-Fi. Apparently its Sony's version of a stereo capable VCR due out soon, but I know nothing else about it. Tom Parkin ihuxo!parkin
prgclb (12/15/82)
In his previous message, Tom Parkin asked about Sony's version of stereo VCR. I read a tidbit in Popular Science some months ago, which said that Sony is working on a way to integrate hi-fi stereo sound into the video signal, thus recording it across the full 1/2-inch width of the videotape. Current stereo VCRs try to pack a hi-fi stereo signal in the narrow audio track at the edge of the tape, and while it works, it's not ideal. The magazine guessed that Sony's version would be out in a year or so. This also shows you one other thing -- Sony is going to work damn hard to make sure its Beta format doesn't die at the hands of VHS! If anyone hears more about this, post it! Carl Blesch
avsdS:avsdT:wcl (12/18/82)
Sony has had a device on the market for about a year now that will take stereo audio and record it on a VCR. It is audio-only, meaning you get *very* good audio (16-bit samples, 30kHz, I think) but no video. Also, it is $600 <= cost <= $1000. If Sony is working on a VCR with internal digital (PCM) audio, it probably uses the same technology. Basically, it works by using the extra space at the end of a scan line. Because home receivers underscan severly, there is an easy 10 microseconds every scan line (= 64usec). You run the audio through a PCM encoder, buffer it thru a FIFO, and spit it out at the end of each scanline. It's relatively easy, and it's surprising no one has done it before. Bet on better than audio-cassette quality when it comes out. Bill Lindemann atd!avsdT:wcl AMPEX Corporation
jim (12/20/82)
Sorry to post this directly, but ucbvax isn't forwarding to atd. Regarding wcl's suggestion of putting a piece of audio at the end of each video scan line: 10 usec is about 1/6th of a scan line. If you put the whole 10 usec at the end of the line, you would need an underscan of 1/3 (1/6 each at left and right of screen) if you didn't want to see the audio. Most home TVs don't underscan *that* badly! Even if you divided it between left and right, you would still need a 1/6th underscan. I keep my TV adjusted to about 10% underscan. Even 10 usec may not be enough, though. If you sample at 30K/sec, you have 1000 samples per frame, or 2 per scan line. At 12 bits per sample (just about the minimum for good audio), for two channels of audio you would need to cram 48 bits into that 10 usec, which is really pushing it for the typical home VCR's bandwidth of 3MHz or so. Which is not to say it isn't a good idea! I had thought of using the vertical interval, which just isn't big enough, but I never thought of trying to use the wasted underscan space. With a little technological ingenuity I'm sure this could be made to work.