Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site psivax.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!lll-crg!dual!qantel!hplabs!sdcrdcf!psivax!jerry From: jerry@psivax.UUCP (Jerry Askew) Newsgroups: net.video Subject: Re: HiFi Compatibility With Dolby Stereo? Message-ID: <632@psivax.UUCP> Date: Wed, 7-Aug-85 20:45:03 EDT Article-I.D.: psivax.632 Posted: Wed Aug 7 20:45:03 1985 Date-Received: Mon, 12-Aug-85 08:24:37 EDT References: <668@ihu1g.UUCP> Reply-To: jerry@psivax.UUCP (Jerry Askew) Distribution: net Organization: Pacesetter Systems Inc., Sylmar, CA Lines: 36 First off, forgive me if the format is kind of dull because this is my first article. In the beginning...(of VHS tape,) the format was quite simple. The tape was divided into 3 sections. Starting from the top, the first section was allocated for audio. The audio track is about 1mm in thickness and contains audio information recorded in the usual format that we are all used to (linear recording, just like cassette tape.) The second section is dedicated to the video information (More on that later.) The third section is given to the control track. This track, also 1mm wide, contains a 30hz pulse that helps the recorder to synchronize its video heads with the video information that is on the tape. Video information is laid down in the video area using a recording technique known as helical scanning. The video information is put on the tape in diagonal 'tracks'. The reason for this is that the spinning action of the heads makes the relative head to tape speed approx 3 metres per sec!!! this gives the necessary fidelity to reproduce a video signal whose upper freq limiit approaches 4mhz! Somewhere along the line, some brilliant engineer figured that if video could benifit from the extrordinary bandwidth & flattness of helical recording, why couldn't audio?? Hi Fi was created. The only problem now is where to put the helical audio tracks. A new recording technique was developed...called deep layer recording. Hi Fi audio information is recorded UNDERNEATH the video information, therefore you have 2 independant stereo audio 'channels' on a hifi recorder. The summary of the above is that hifi audio is COMPLETLY seperate from standard 'linear' stereo audio & should have no effect on the operation of a 'linear' recorder. Most tapes that have hifi tracks on them are recorded in dolby stereo but this is not required. Hope that my fist try helped somebody! Jerry Askew psivax!jerry