Abstract: A method and apparatus are disclosed for enabling the continuous monitoring of recording circuit performance and the automatic optimization of the recording process in a rotary head recorder having a plurality of recording heads. A calibration signal is recorded by each recording head onto the overlap area of a moving magnetic tape medium. A fixed monitor head subsequently detects components of the recorded signal, the magnitudes of which are squared and retained in sample and hold units. The sampled and held values are periodically used to construct an outputted value commensurate with recording circuit performance. Optimization is accomplished by varying the recording drive level of a recording head about a predetermined point during a series of successive overlap periods. A DC error voltage is derived from the respective outputs resulting from such variation, and used to shift the recording drive level of that head towards a point of optimum playback output.

Abstract: A method and apparatus are disclosed for eliminating or dropping digital samples from a data stream of samples to reduce the data rate for transmission of the data stream through a transmission channel, such as a data record and reproduce system or the like, and for subsequently reconstructing the original data stream by using the unaltered and recovered digital samples to generate an interpolated value for each of the samples that has been dropped. A finite impulse response multi-term digital filter is used to generate the interpolated value for the samples that have been dropped. Advantages reside in the fact that errors are not propagated during multiple generation recording or transmission, since unaltered sample values are always used to produce the interpolated value for the dropped sample that is being reconstructed. The invention has particular use in video recording and reproducing wherein it is desirable to record a digital data stream at the lowest practicable data rate.

Abstract: A method and apparatus are disclosed for performing a reduction of the data rate of a data stream for transmission through a transmission channel or recording and for subsequently reconstructing the original data stream upon receipt or during reproducing. The method and apparatus utilizes a combination of two processes, one of which eliminates or drops digital samples from the data stream to reduce the data rate for transmission and which subsequently reconstructs the original data stream using the unaltered and recovered digital samples to generate an interpolated value for each of the samples that had been dropped. The second process utilizes differential pulse code modulation for reducing the number of data bits per sample before sending the data stream through the transmission channel and for subsequently restoring the data to its original multi-bit form.

Abstract: A system is described for determining the position of a magnetic read head relative to the center of a selected data track on a magnetic recording medium moving with respect to the read head. Tracking signals of equal frequency, but out of phase a predetermined fixed amount, are recorded on adjacent data tracks. The tracking signal frequency is selected to be a long enough wavelength such that a single read head positioned over a selected data track also detects the tracking signal recorded on adjacent data tracks. A phase comparator compares the phase of the tracking signal detected by the read head with respect to the phase of a reference signal of equal frequency, and a resultant signal is generated which is indicative of any deviation of the read head from the center of the selected track.

Abstract: A magnetic recorder including a playback circuit for decoding a ternary waveform digital data signal is disclosed, wherein positive and negative threshold levels, used to distinguish between signal levels representative of data ones from signal levels representative of data zeros, are automatically adjusted to compensate for occasional reductions in overall signal level that can occur due to dropouts and modulation noise on the magnetic medium. Two sample and hold units are used to generate an output signal whose amplitude reflects only those signal levels that are greater than some minimum absolute value. This output signal is filtered and then used to generate the compensated positive and negative threshold levels.

Abstract: A time-base correcting system primarily adapted for use in video tape recording equipment and providing synchronous lockup and time base corrected operation of the video-tape recorder in the playback mode. The system includes circuitry receiving phase alternating line (PAL) composite television signals and which determines the burst switching sequence of the recorded signal before stable lockup is achieved.