Apparatus and method for transmitting audio signals as part of a television video signal
OwnerJ. Carl Cooperinventor
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Abstract
The apparatus and method is shown for transmitting one or more audio frequency signals on a television video signal including an encoder comprised of a pulse modulator responsive to the audio frequency signals and a combiner to combine modulated pulses from the modulator with the video signal. Also shown is a decoder for use with video signals output from above encoding apparatus and method for decoding the modulated pulses to recover the audio frequency signals.
Claims14
An apparatus for combining a video type signal with samples of a secondary signal, said video signal having a varying horizontal line rate, a secondary signal sampling and modulation circuit, said secondary signal sampling and modulation circuit operating at a first rate, said first rate being dependent on said varying horizontal line rate of said video signal, a timing circuit, a switch circuit, a combining circuit, said switch circuit applying said modulated samples to said combining circuit when appropriate, said timing circuit operating at a second rate, said second rate being dependent on said video signal, said second rate having an average, said average of said second rate equalling said first rate of operation of said secondary signal sampling and modulation circuit said timing circuit, said switch circuit, and said combining circuit encoding samples of said secondary signal with said video signal.
The method for combining a secondary signal with a video type signal having a synchronizing portion, said secondary signal having a relatively lower bandwidth, including:
- sampling said secondary signal, using a difference modulator and providing a modulated signal responsive to the differences of said samples;
- storing said modulated signal in a memory at a first rate;
- reading said modulated signal from said memory at a second faster rate;
- and combining said modulated signals which are read from said memory with said video type signal in a manner which preserves said synchronizing portions thereof.
The method for combining a secondary signal which is a digital modulated version of a relatively lower bandwidth signal with a video type signal having a synchronizing portion, including:
- sampling said relatively lower bandwidth signal in response to said video type signal;
- providing said secondary signal in response to the differences of said samples obtained in said sampling step;
- storing said modulated signal in a memory at a first rate;
- reading said modulated signal from said memory at a second faster rate;
- and combining said modulated signal which is read from said memory with said video type signal in a manner which preserves said synchronizing portion thereof.
An apparatus for encoding a video signal which may have a varying horizontal line rate with samples of a secondary signal, said apparatus having a difference amplifier, a first integrating amplifier, a first clock, said difference amplifier having an output equal to the difference between said secondary signal and a preceding secondary signal generated by said first integrating amplifier, said output of said difference amplifier being periodically sampled by said first clock generating periodic samples, a second clock, said second clock operating at a first rate dependent on said varying horizontal line rate of said video signal, a first modulation circuit sampling said periodic sample of said output of said difference amplifier at said rate of said second clock producing modulated samples, a timing circuit, a switch circuit, a combining circuit, said switch circuit applying said modulated samples to said combining circuit when appropriate, said timing circuit operating at a second rate, said second rate being dependent on said video signal, said second rate having an average, said average of said second rate equalling said first rate, said timing circuit, said switch circuit, and said combining circuit encoding samples of said secondary signal with said video signal.
Dependencies are inferred from the claim text.