lionel@orphan.DEC (Steve Lionel) (01/21/85)
>> I am now thoroughly confused regarding the distinction >> which is painstakingly made by the various VCR manufacturers between >> a "STEREO" unit and a "HI-FI" unit. I thought the difference was merely > Once again, almost every VCR on the market today is STEREO. It has two > tracks along the edge that are roughly equivelent fidelity to a crappy > cassette. HIFI multiplexes a higher fidelity audio track in with the > video and is layed down withh the video head. Many VHS VCRs, but not "almost every", are indeed low-fi stereo that is far worse than audio cassettes. The only Beta stereo VCRs are also Hi-Fi. Only Beta Hi-Fi multiplexes the audio with the video - VHS uses separate heads to record the audio information separately. >> I've come across those who tell me that the two >> audio formats are incompatible, that the stereo movies I have purchased >> will not reproduce stereo in a HI-FI recorder system. > They are incompatible, but that doesn't mean they can't coexist. I would > venture to say that all HIFI decks are perfectly able to replay the old > stereo signals when the HIFI isn't on the tape. The Beta HIFI tapes may > also be played on non-hifi machines because they also record the old style > stereo tracks as well. VHS detracters say VHS HIFI tapes can't be played > on older machines without degredation of the video component. I don't know > if this is true, or just SONY propaganda. VHS Hi-Fi tapes can indeed be played on non-Hi-Fi VCRs, but you might not get what you expect. Some VHS Hi-Fi VCRs don't record or play the standard audio track in stereo, and some which do don't have Dolby circuitry (a few have a high-cut filter for playing Dolbyized tapes). The result is that if you play a tape recorded on one of these VHS Hi-Fi VCRs on a non-Hi-Fi deck, you may not get stereo or Dolby. I would expect that commericial prerecorded tapes would play normally. Whether the VHS Hi-Fi recording method degrades the video (even more than it is already degraded for VHS :-)) remains to be seen. I can't see how you can help but lose some signal when you deliberately try to keep two different signals in the oxide. Steve Lionel
ron@brl-tgr.ARPA (Ron Natalie <ron>) (01/28/85)
> > Many VHS VCRs, but not "almost every", are indeed low-fi stereo that is > far worse than audio cassettes. The only Beta stereo VCRs are also > Hi-Fi. Only Beta Hi-Fi multiplexes the audio with the video - VHS uses > separate heads to record the audio information separately. > VHS doesn't encode the HI-FI on the video head. If this is true that explains why Sony kept claiming it would be impossible for VHS to do HI-FI without degrading the video. Anybody know for sure? -Ron
jeh@ritcv.UUCP (Jim Heliotis) (01/28/85)
> VHS doesn't encode the HI-FI on the video head. If this is true that > explains why Sony kept claiming it would be impossible for VHS to do > HI-FI without degrading the video. Anybody know for sure? > > -Ron Many people who do know for sure have already explained this, but perhaps not in a clear enough way, so I'll make a stab at it. The Meaning of "HEAD": This has two popular meanings. The 'real' one is each of the set of little things spinning around in your VCR, or the things you have in any tape recorder for audio. This is what is being referred to when salesmen brag about 3-, 4-, or 6-head VCR's. The other popular use is to use "head" to mean the spinning metal cylinder, the drum, which holds all the video (and VHS HiFi, see below) heads. In all video tape recorders, the video information components are modulated at various frequency bands and sent out to the video heads for recording. The bands chosen for Beta are more spread out than those chosen for VHS. Therefore, when SONY decided to build in HiFi sound, all it did was use one of the "spaces" between the video bands and use it to modulate the 2 audio channels. Therefore, to play the audio, you just use the video heads, and then employ circuitry to separate/filter out the audio bands. SONY said that VHS could not do this, due to lack of space between video bands, (they could if they narrowed the video bandwidth, causing picture degradation, in order to create spaces for audio) and they are right. So instead, VHS decided to first record the HiFi audio information on the tape, using frequencies which conflict with the video signals, but write to the tape "at a different angle" (that's as technical as I feel it's safe for me to get). Then, the video is written "on top of" the audio signals. It turns out that it is possible to extract both types of information off the tape if /different\ heads are used to read the information at the same angles at which they were written. Thus we have a situation where extra audio heads are placed on the video drum to make VHS HiFi. So, an n-head Beta HiFi machine is potentially equivalent to an (n+2)-head VHS HiFi machine, and I wonder how many people know that. Hope this makes things clearer, without my being wrong! Jim Heliotis {allegra,seismo}!rochester!ritcv!jeh rocksvax!ritcv!jeh ritcv!jeh@Rochester
howard@amdahl.UUCP (Howard C. Simonson) (02/01/85)
> ... > Thus we have a situation where extra audio heads are placed on the video > drum to make VHS HiFi. So, an n-head Beta HiFi machine is potentially > equivalent to an (n+2)-head VHS HiFi machine, and I wonder how many people > know that. > > Hope this makes things clearer, without my being wrong! > > Jim Heliotis > {allegra,seismo}!rochester!ritcv!jeh > rocksvax!ritcv!jeh > ritcv!jeh@Rochester Well, that had to be about one of most concise and well written explanations of the whole shebang I have read in a while. And from my alma matter no less. Tell me one thing though, does the tape speed have any bearing on audio fidelity? -- ------------------------------------------------------------------------------- Do not walk in front of me, I may step on your heel. Howard C. Simonson Do not walk behind me, ...{dragon,hplabs,ihnp4,nsc}!amdahl!howard I may stop abruptly, Just walk beside me, and be wary of sharp turns. -- HamuS [ The opinions expressed <may> be those of the author and not necessarily those of Amdahl Corporation, its management, or employees. ]