Ampex Corporation

Reginald W Oldershaw

Steven D Wagner

Edwin S Busby, Jr

Jan S Wesolowski

Kenneth Louth

Robert B Steele

John Hutson

A dynamic head position tracking control for a magnetic tape playback system employs a detected dither signal to determine the elevational position of a pair of magnetic transducing heads relative to tracks of recorded information being scanned by the heads. This detection is carried out at several locations along the lengths of the tracks being scanned, and a value is stored for each of the locations. Based upon the stored information, an estimation is made of a position value for the first location along the length of the tracks. This estimation is determined from a weighted extrapolation of the following two samples taken during the scan of the track. The elevational position of the heads is then dynamically controlled in accordance with the actual and estimated head position values.

Dynamic head position tracking control for a magnetic tape playback

Plural magnetic transducing heads are employed to record and reproduce video information that is stored in a segmented format. One head is in contact with the magnetic recording tape while the other head is out of contact with it. The position of the head which is in contact with the tape is controlled by a suitable ramp voltage generated in accordance with the ratio of actual tape speed to normal play speed, to maintain the head generally aligned with a track on the tape. The other head, which is out of contact with the tape, is also positioned in the same fashion. When a repositioning of the heads is required, a determination is made whether the track of information being reproduced by the head in contact with the tape relates to a particular segment of a field, for example the last field. If so, the head which is out of contact with the tape is appropriately repositioned so that it is in the proper location when it comes into contact with the tape to begin scanning the first segment associated with the next field that is being reproduced. Once the other head has come out of contact with the tape at the end of the previous field, it is repositioned to bring it to the location of the head which is now in contact with the tape.

Automatic head position tracking system for video signals recorded in a

There is disclosed herein a system for digitally forming synchronization signals. In the preferred embodiment, these synchronization signals are for substitution in place of the original synchronization signals in a television signal. These digitally generated synchronization signals are generated synchronously with the digitization of the video portions of the television signal, and the digitally generated synchronization signals are multiplexed into the stream of digital video data in the appropriate blanking intervals. The system uses a first digital signal number generator to generate a plurality of digital signals which represent the peak amplitudes of the desired synchronization signals. A second digital signal number generator synchronously generates a second plurality of digital signal values representative of the shape of the desired edges for the synchronization signal being generated. The second first and second digital signal number generators are synchronized with the clock controlling the input of the digitized video signals into the system and receive reference signals indicating when the first and second pluralities of digital signal values are to be generated and their intervals. During the appropriate blanking interval, the first and second pluralities of digital values are multiplied, and the products are output to be added to the input video signal. During times other than the blanking intervals, the incoming digitized video is multiplied by a digital gain value. The resultant stream of digital values are coupled to a digital to analog converter. The resulting analog level signal is passed through a low pass filter having specific characteristics to derive the analog television signal. There is also apparatus to allow the user to digitally adjust the sync to subcarrier phase by selecting a different one of a family of sets of digital transition edge gain control values.

Digital envelope shaping apparatus

A digital time base corrector for correcting time base errors of the digital samples of a video signal for all the various speed modes of a reproducing apparatus. The time base corrector is configured having a small capacity memory and a large capacity memory wherein the small capacity memory is divided into a first section and a second section. The first section of the small capacity memory retimes data samples for subcarrier phase errors without losing or repeating data, while the second section of the small capacity memory retimes data for horizontal frequency error without losing or repeating data in all reproducing modes except shuttle. Further, the second section of the small capacity memory in reverse and forward shuttle retimes the data for horizontal frequency and phase errors while equalizing the data rate through the time base corrector by selectively discarding or repeating horizontal lines based on line type. The large capacity memory in all reproducing modes except shuttle retimes data for timing errors of line and field phase while in shuttle the memory retimes for field phase only.

Time base corrector with accurate timing corrector control

An adaptive dropout compensator is fully digital and employs an adaptive logic circuit to detect dropout characteristics such as the extent thereof and the best available replacement data, and generates an adaptive logic decision for supplying the optimum replacement data. The circuit configuration lends itself to a switchable implementation for accommodating the various color television standards.

Multi-standard adaptive dropout compensator

A video signal correction circuit of a signal processing system includes means for determining the chroma line type, for inserting the line type information in the video signal, and for extracting the line type information from the video signal downstream to allow selecting the phase of the chroma subcarrier to match the phase of the output station reference.

Chroma phase word encode/decode in a video processing system

A tape speed measuring circuit for use with quadruplex video recorder/reproducers, which identifies the speed at which the recording was made to allow automatically switching to the correct speed upon playback. The circuit measures the ratio of control track frequency relative to the capstan tach frequency to obtain the recorded tape speed. A commutating filter means responsive to the capstan tach signal allows the accurate extraction of the desired control track signal component at all tape speeds. Divider means counts the number of tach pulses received during a selected time period. If the number of pulses is more or less than a pre-selected quantity, a high or low logic level respectively is generated commensurate with the standard 15 or 71/2 inches/second recorded tape speed.

Method and apparatus for measuring the speed at which a tape was recorded

An error corrector circuit for correcting a tape timer in a video tape recorder/reproducer (VTR) having a multiple frequency control track, wherein a selected control track frequency is separated from the composite frequencies via commutating filter means capable of following frequency variations caused by variable tape speeds. The resulting filtered control track signal of selected frequency is phase compared with a tach clock signal of similar frequency obtained from the capstan tachometer. In the absence of slip, creep, tension variations, and other speed errors caused by playing the tape on different devices, there is no phase difference between the compared signals, which are thus phase locked together. Any phase deviations between the filtered control signal and the tach clock signal are detected and fed back to correct the tach clock signal so that it accurately represents the passage of tape past the VTR head means. A television frame rate pulse output derived from the corrected tach clock signal is fed to the tape timer of the VTR.

Tape timer error corrector circuit for tape recorder/reproducers

An unknown tape pack diameter is determined by measuring the inertia of the unknown tape pack and comparing the inertia with an inertia value representative of the inertia of a second tape pack of known diameter.

Growing community of inventors

Redwood City, CA, United States of America

Reginald W Oldershaw