Ampex Corporation

Leonard A Pasdera

Maurice G Lemoine

Sohei Takemoto

Robert B Steele

Apparatus and methods for encoding information of one class into the parity for main data of another class. One such method and apparatus fundamentally takes one member A.sub.x of a limited first class of data called attribute data and concatenates it with main data. Parity is then calculated on the concatenate word. After the main data and parity is transmitted or recorded, the selected member of the first class of data may be recovered by comparing the received parity to the parity P' generated on the receiver side using the main data and each member of the first class of data to generate a plurality of syndromes. The first all zero syndrome identifies the member of the first class which was encoded into the parity of the main data. Another method and apparatus are similar except that the transmitter side calculates parity P.sub.ax for the selected member of the first class and then encodes that parity into the parity calculated for the main data. On the receiver side, parity bits are calculated for each member of the first class and then combined with parity P.sub.d ' calculated on the main data to generate parity P'. This parity P' is then compared to the received parity P', and the first match indicates which member of the first class was encoded on the transmitter side.

Apparatus and method for encoding and decoding attribute data into error

A technique for recovering helical audio using the standard synchronous reference clock of the video tape recorder system to conventionally clock the transport and the video signal processor, including the video timebase corrector. A modified audio signal processor clock is generated which is varied commensurate with the desired rate of tape speed override, varying accordingly the flow of audio data through an audio timebase recorder. The speed of a helical scanner is varied in accordance with the rate of tape speed override, to lock the scanner angular position to the audio timebase corrector. In turn, a capstan servo adjusts the tape position in respsonse to the scanner angular position to lock the tape to the scanner. Meanwhile, the video signal processing proceeds conventionally by skipping or repeating fields or frames via a frame store to match the rate of tape speed override.

Method and apparatus for tape speed override operation when recovering

Errors in data words recovered following the transmission of digital data having internal correlation are concealed by substituting recovered correlated words for recovered words suspected of being in error. Concealment may follow the correction of errors according to an error correcting code. Error flag signals are used to identify corresponding respective recovered words that are suspected of being in error. These error flag signals are counted over a predetermined totaling interval, and a concealment interval signal is generated for a concealment interval when the count exceeds a predetermined threshold count. Recovered correlated words are substituted for recovered words corresponding to respective error flags and for all other recovered words corresponding to a respective concealment interval. In accordance with one aspect of the invention, the concealment interval is centered upon the corresponding totaling interval. According to another aspect of the invention, the concealment interval signal is generated upon the occurrence of an error flag signal while the count exceeds the predetermined count. Also, the concealment interval signal is preferably restarted upon the occurrence of a subsequent error flag signal while the count exceeds the predetermined count.

Digital signal error concealment

A deskew processor includes first and second memory units each having independent data write control circuits and data read control circuits. The write control loads successive data into respective memory units as it is received, and the read control reads the data out of the memory units into a data selector circuit as determined by a data selector control circuit. The latter determines the presence of any data overlap and delays read out of data via the data selector circuit until the previous data is completely read, thereby deskewing the successive data.

Apparatus for deskewing successively occurring blocks of data

A method and apparatus is disclosed for recording and reproducing color television signals on a magnetic media such as magnetic tape, wherein the signals recorded on and reproduced from the magnetic media are in a digital domain. The analog color television signal is converted to digital signals in a manner whereby the horizontal blanking interval is compressed and digital synchronizing information is inserted in the compressed horizontal blanking interval for every line. Upon reproduction, the digital synchronizing information is extracted from the reproduced information and is provided to servo circuits for controlling the relative transport of the magnetic tape and operatively associated magnetic heads to effect synchronous reproduction of the recorded information relative to a reference signal.

Method of controlling apparatus for recording and/or reproducing on a

A method and apparatus is disclosed for recording and reproducing color television signals on a magnetic media such as magnetic tape, wherein the signals recorded on and reproduced from the magnetic media are in a digital domain. The apparatus utilizes a rotating head wheel having a plurality of transducing heads spaced around its circumference which operate to record and reproduce the digital data transmitted through two separate channels at a very high data rate. The analog color television signal is converted to digital signals in a manner whereby the horizontal blanking interval is compressed and digital synchronizing information is inserted in the compressed horizontal blanking interval for every line. The portion of the real time horizontal blanking interval for which recording is not performed enables time base correction to be accomplished on an individual line by line basis. The digital television signal is processed through memory during recording to enable recording of the data on two channels at a slower than real time rate. During reproducing, the data is again processed through memory and is converted back to real time rate and then converted to an analog signal to which typical synchronizing signals are added.

Method and apparatus for digital video signal processing

Apparatus is disclosed for acquiring and maintaining a generally continuous clock signal from a very high frequency encoded data stream of the type which is self-clocking and has logic state transitions occurring at two locations within each bit cell of the data stream. The apparatus is particularly useful in decoding apparatus, such as may be used in a magnetic recording and reproducing system. The apparatus effectively generates the clock signal from the encoded data stream and reclocks the data stream utilizing the generated clock signal to accurately position the logic signal transitions within the bit cells and thereby assure accurate decoding of the data. The apparatus processes two simultaneously transmitted synchronous data streams, and has the capability that permits the generated clock signal from one data stream processed in one channel to be used to maintain synchronization of the other processing channel notwithstanding a loss therefrom of the data stream for short periods of time.

High frequency digital PCM decoding apparatus

Apparatus is disclosed for providing compensation for missing, incorrect or otherwise defective data in a data stream preferably comprised of video information. The apparatus is particularly useful in a magnetic recording and reproducing system for digital video data signals. The apparatus effectively stores the digital video data that occurred 262 video lines prior to the current data at the input and continuously updates, (i.e., stores in place of) the stored data with current data unless defects occur in the current data, in which case the defective current data is not stored. The data from the store is inserted in the video data streams when the drop-outs or parity information associated with the data stream indicates that the current data is defective. By inserting digital data which represents data that occurred 262 horizontal lines previously, the content of the substituted video information has a high probability of being visually equivalent to that of the original current data, since in most cases, it represents data from an adjacent horizontal line in a prior television field. The apparatus inhibits writing of data during substantial portions of the horizontal and vertical blanking intervals and thereby reduces the capacity of the storing means which is required to provide compensation for essentially a full field of active video information.

Apparatus for providing drop-out compensation in recording and

Apparatus is disclosed for providing error compensation for a digital video information signal and is particularly adapted for use with a format video information signal. The apparatus takes advantage of sampling being done in a precise manner, i.e., at a rate of four times the chrominance subcarrier frequency of the information signal, and alternately along the U and V vector axes. The apparatus generates a substitute value for a defective sample that is the average of selected samples which are in close proximity to and which are of the same type as the defective sample. More particularly, replacement samples taken along the U vector axis (U samples) are generated by averaging the nearest in proximity U samples and the replacement V samples are obtained by averaging the nearest in proximity V samples. Switching means appropriately substitute the generated values for the defective values so that V samples replace V defective samples and U samples replace defective U samples.

Apparatus for providing error compensation in a digital video recording

A method and apparatus is disclosed for controlling the sampling of a composite analog color video signal so that the analog signal is sampled at precise locations relative to the phase of the color subcarrier of the color video signal in the absence of modulation. The invention thereby enables a digitized signal having a constant phase relationship relative to the unmodulated subcarrier phase to be provided which can be advantageously used in magnetic recording and reproducing apparatus. Since the constancy of the location of the samples relative to the phase of the color burst is maintained prior to recording, there is no phase error that would pose a problem during reproducing of the signal. The apparatus stores a set of reference samples of a selected number of cycles of the color burst interval of the color video signal and generates an output clock signal that is phase synchronized with the reference samples, subsequently stores sets of comparison samples of color burst cycles from subsequent horizontal video lines using the generated clock signal and detects any error in the phase location thereof. The apparatus adjusts the phase of the generated output clock signal in response to any detected error signal and stores a new set of reference samples in the event that the error detected is beyond predetermined limits.

Fast acting phase shifting apparatus for use in digital sampling systems

A time displacement adjustment device compensates time base errors that progressively cumulate in a time varying signal having a synchronizing information component from which the signal time base can be determined. Periodically, the synchronizing component is sampled and a representation thereof continuously generated with the component's timing relationship to the signal retained. Each continuously generated representation and the succeeding sample of the synchronizing component are compared to determine the time base error that progressively occurs in the signal between the successive samples of the synchronizing component. That signal is expanded or compressed accordingly to correct the erroneous timing.

Timing error compensator

In last line velocity compensation of color television signals reproduced by video recorders, the velocity error signal for the next to last line of information before the head switch that occurs during the vertical blanking interval is stored for a time extending beyond the period of the last line. The switching between transducers that occurs during each vertical blanking interval is delayed so that a color burst signal following the last line is reproduced and a velocity error for the last line generated. This last line velocity error signal is differentially compared with the stored next to last line velocity error to provide a velocity error difference signal. The error difference signal is stored for the period between the foregoing and succeeding vertical blanking intervals. The stored velocity error difference signal is added to the velocity error of each of the next to last lines of video information reproduced before switching between transducers at times between such vertical blanking intervals to provide last line velocity error compensation for those intervening last line.

Growing community of inventors

Redwood City, CA, United States of America

Leonard A Pasdera