Browse Prior Art Database

Video Cassette Recorder Digital Recording

IP.com Disclosure Number: IPCOM000060997D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Tran, LT: AUTHOR

Abstract

This article describes a method to record computer data onto a video cassette tape using both asynchronous and synchronous encoding. The servo subsystem is one of the most essential mechanisms in a helical scanning system video cassette recorder. It is responsible for positioning the video heads to the tape correctly during record operation, and is responsible for aligning the video heads over the recorded video track correctly to reproduce the video signals during the playback operation. The vertical sync separated from the input video signal is recorded onto the control track of the video tape, and it is also used to control the servo subsystem during the record operation. During the playback operation the vertical syncs read off the control track of the video tape are used to control the servo subsystem.

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Video Cassette Recorder Digital Recording

This article describes a method to record computer data onto a video cassette tape using both asynchronous and synchronous encoding. The servo subsystem is one of the most essential mechanisms in a helical scanning system video cassette recorder. It is responsible for positioning the video heads to the tape correctly during record operation, and is responsible for aligning the video heads over the recorded video track correctly to reproduce the video signals during the playback operation. The vertical sync separated from the input video signal is recorded onto the control track of the video tape, and it is also used to control the servo subsystem during the record operation. During the playback operation the vertical syncs read off the control track of the video tape are used to control the servo subsystem. Therefore, in order for a video cassette recorder to function properly, the input signal to be recorded should contain vertical syncs as a minimal requirement. The method disclosed herein records computer data onto a video cassette tape using both asynchronous (with start and stop bits) encoding and synchronous modified frequency modulation (MFM) encoding. A contiguous data block can be recorded between vertical sync intervals instead of horizontal sync intervals. The recording frequency is limited only to the luminance bandwidth of the video cassette recorder. With a recording frequency of 895 KHz, 1024 bytes of data with asynchronous encoding can be recorded during each video field. Fig. 1 shows the asynchronous signal encoding, although MFM can also be used. In this method, the sync level represents a binary zero "0" and the white level represent a binary one "1". When a signal waveform of this type is inputted to a video cassette recorder, the signal waveform itself appears at the output of the sync separation circuitry instead of the standard composite sync signal. Since the data binary zero is at the sync level, this does not cause the video cassette recorder to misinterpret the binary zero to be the vertical sync because a low-pass filter is used to obtain the vertical sync fr...