Robert Boschgmbh

Bts Broadcast Television Systems Gmbh

Jurgen Muller

Jurgen Heitmann

Roland Mester

Rolf Loos

The magnetic tape video playback apparatus for a digital video signal regenerates the sample rate from the playback to operate a counter and detects the video data block numbers to permit an address generator to derive the more significant bits of addresses for a picture memory in which the video data signal is temporarily stored. The counter provides the less significant bits of the write addresses. The separated vertical sync pulses are counted in a second counter to provide time information for storage in a time data memory which is operated in parallel with the picture memory, using the write addresses from the already mentioned address generator. A reference sample rate generator operates a third counter which provides the read out addresses for the picture and time data memories. The memory input and output time data are compared and the time difference is evaluated with reference to a threshold for providing an error flag to an error concealment unit to which the video data read out from the picture memory is supplied for concealing errors resulting from overage video data in the picture memory which may be stored there during playback at high speeds. At low speeds the minimum time difference designates an error.

Method and apparatus for reproducing at a selected speed video signals

For slow motion playback operation with a digital video magnetic tape recording and reproducing equipment an intermediate memory system has four picture field memories of which there are always three available for writing into but only one of them at a time is in read-out operation. In a first reading operation of a particular picture field memory an AND correlation of a write flag and an error flag is necessary for providing an error recognition signal to following circuits and before a reading goes to the next address the write flag is erased by writing in a logic zero, but the correlated signal is used to rewrite the error flag in the error flag memory. In subsequent readings any error flag is transmitted and rewritten, but all write flags remain erased to signify that the memory has been read out at least once.

Intermediate picture field storage system for slow motion playback of

Data blocks recorded on oblique tracks on magnetic tape are preceded by synhronizing signals and block identification signals. The serial data identification signals are converted to 8-bit parallel form and then are split between an undelayed channel and a channel delayed by one data block. Under control of a sync detector the parallel data are made to correspond with data words and are then decoded for comparison of the block numbers. Since the block numbering is consecutive, the delayed decoded block number is incremented by one for comparison. When a positive comparison is obtained the block number of the delayed decoded signals is made available to identify the data block. A counter in a so called fly wheel circuit assures provision of a new block start signal if a synchronizing signal is missed and prevents the timing of the circuit from being put off by a false detection of a synchronizing signal. A block identification output appears only if its block number is in sequence.

Method of cross-checking data block identification signals of data

Four picture field memories which contain storage places for luminance data, chrominance data, error flags and write flags are switchable from write in to read out by changeover switches controlled by an access control unit for connection of the address and control inputs of the memories either to a write in control circuit or a read out control circuit. The access control unit can be set for operation at normal speed, which is the recording speed of the tape from which signals are read out, below normal speed or above normal speed. The read-out control circuit is synchronized by a synchronizing signal that contains a vertical scan frequency reference pulse. The several picture field memories are cyclically interchanged, written into and read out from. One of the picture field memories is read out while the others are available for write-in. The incoming error flags are passed on. Use is made of write flags and error flags to improve operation at speeds different from the recording speed.

Intermediate picture field storage system for variable speed magnetic

To prevent, cross-talk and other signals from being applied from the magnetic transducer head (6, 7) to an output circuit (12, 13; 28, 29) in a video tape reproduction system, in which one of the heads, only, is in contact with the tape, and the other head runs free, a synchronizing signal recognition stage, responding to the first appearance of a synchronizing signal at one of the heads, is connected to control a switch, typically an electronic switch, to transmit the signals from the specific head to the output circuit and disable signal transfer of any signals from the other one of the heads since those signals, usually, would be noise or disturbance signals. When a synchronizing signal, then, is received from the other head, which previously was disconnected, the circuit switches over to disable the first one and transmit only signals from the second head, so that electronic switching is provided based on recognition of signals transduced from the tape itself, typically and preferably synchronizing words in a digitally recorded TV signal.

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Griesheim, Germany

Jurgen Muller