Abstract: Recovering data (e.g., closed captioning data, teletext data) encoded in television signals. A line encoding the data is over-sampled. The resulting samples are examined to determine the average number of samples spanning the low and high values in a run-in period. The average numbers are used to determine the sampling clock and the samples which represent the encoded data. By using the two average numbers, any errors which may be otherwise encountered due to factors such as ghosting may be eliminated or avoided.

Abstract: A circuit for recovering the data encoded in several VBI channels without requiring a large number of gates. An analog to digital converter (ADC) and a clock and data recovery circuit may be associated with one of several possible channels. ADC over samples each VBI channel, and clock and data recovery circuit determines which subset of the over samples represent the encoded data by examining the over sampled samples. The selected subset may be stored in a shared memory and a equalizer may process the subset of samples of all channels to perform tasks such as deghosting. Due to the shared equalizer, the number of required gates may be minimized.

Abstract: A circuit for recovering the data encoded in several VBI channels without requiring a large number of gates. An analog to digital converter (ADC) and a clock and data recovery circuit may be associated with one of several possible channels. ADC over samples each VBI channel, and clock and data recovery circuit determines which subset of the over samples represent the encoded data by examining the over sampled samples. The selected subset may be stored in a shared memory and a equalizer may process the subset of samples of all channels to perform tasks such as deghosting. Due to the shared equalizer, the number of required gates may be minimized.

Abstract: A method of recovering synchronization signals contained in a composite video signal. The synchronization signals are generally represented by voltage levels less than the blanking level of the video signal, and display data is represented by blanking level. A digital circuit controls a biasing circuit to generate a biasing voltage. A video signal is biased using the biasing voltage and the resulting biased video signal is provided as an input to an operational amplifier. A second input of the operational amplifier is driven by a reference voltage. The digital circuit monitors the output of the operational amplifier and controls the biasing voltage to cause the operational amplifier to clip the display data from the biased video signal and generate a signal representing synchronization signals.