Recording and/or replaying teletext signals
AssigneeU.S. Philips Corporation
InventorShirley J. James
Life of this patent
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Abstract
Standard binary teletext signals (which have a data rate exceeding the bandwidth of a standard VHS video recorder) are converted into a multilevel code so that the teletext data can be reliably recorded and replayed by a standard VHS video recorder. During recording teletext data is received at a high data rate and encoded in accordance with a multilevel code at a lower data rate and within the bandwidth of the VCR. During playback the multilevel code is decoded back into binary code at the standard teletext data rate and clock run-in and framing codes are added to provide standard teletext signal. The resulting teletext data is then combined with the video signal.
Claims27
A method of recording teletext data comprising the steps of:
- receiving teletext data at a standard data rate of teletext data;
- converting the teletext data to a multilevel code having more than two code levels, at a data rate which is lower than the standard data rate of the teletext data, the converting comprising applying the received teletext data to an encoder in n-bit packets, where n is greater than one, and converting each n-bit packet into the multilevel code, the multilevel code having at least one level for each n-bit combination;
- and
- recording the multilevel code on a record carrier at a data rate of 1/n times the standard teletext data rate.
A method of replaying teletext data comprising the steps of:
- reading a multilevel code from a record carrier at a data rate of 1/n times a standard data rate of teletext data, where n is greater than one, the multilevel code having more than two code levels;
- converting the multilevel code to standard teletext data in n-bit packets, and
- applying the teletext data to a teletext encoder.
Apparatus for recording teletext data, comprising:
- means for receiving a video signal including teletext data,
- means for detecting received valid teletext data,
- means for encoding the received teletext data into a multilevel code having more than two code levels, at a data rate which is less than the standard teletext data rate, the means for encoding including means for applying the received teletext data to an encoder in n-bit packets, where n is greater than one, and means for converting each n-bit packet into the multilevel code, the multilevel code having at least one level for each n-bit combination and
- means for recording the multilevel code on the record carrier at a data rate of 1/n times the standard teletext data rate.
Apparatus for replaying teletext data, comprising:
- means for feeding a multilevel code signal having more than 2 code levels, at a data rate of 1/n times a standard data rate of teletext data, where n is greater than one, to a decoder to convert the multilevel code to a binary code in n-bit packets at the standard teletext data rate;
- and
- means for multiplexing the binary code with the video signal for application to a teletext decoder.
The apparatus of 18 in which the equalizer is a decision feedback equalizer.
Dependencies are inferred from the claim text.