DE3735565C2 - Storage arrangement for a digital video tape device - Google Patents

Description

The invention is based on a memory arrangement according to the Genus of the main claim.

In a known method for magnetic storage of digitally encoded television signals are after sampling the analog values, quantization and coding with addition the data from identification and data backup values transferred serially in blocks. Because of the total necessary large transmission capacity is known Magnetic tape devices for recording and / or playback digitally encoded television signals a record in four parallel channels with correspondingly smaller Transmission bandwidth provided. For recording or Reproduction is even at the circumference of a head wheel Intervals four magnetic heads arranged. Of the Wrap angle of the magnetic tape around the head wheel is 258 °. The four magnetic heads kick the one after the other Magnetic tape in contact and describe the magnetic tape with associated, obliquely to the longitudinal axis of the magnetic tape  trending tracks. These each contain two Track sections, called sectors, with video data recorded in the Area of the central axis of the magnetic tape by several short Track sections, the different sound information included, are separated. Each track section (sector) contains video data different from the other sectors.

When playing, precautions should be taken that everyone of the four magnetic heads reads out the data through it or a same magnetic head of another device after the same models were also recorded. The special one Arrangement of the track sections with the video data on the Magnetic tape makes the switching of the magnetic heads before and according to the sectors intended for video data from one Video data channel on another specific video data channel required. This is done after a recording established scheme that changes after every turn of the top wheel repeated.

Details are in the Publication "Standard for Recording Digital Television Signals on Magnetic Tape in Cassettes "by European Broadcasting Union, Tech 3252-E and in TV and Kinotechnik 1987, issue 1/2, pages 15 to 22.

When playing, measures must be taken that the on four channels of distributed video data correctly composed become. According to DE 37 18 567 A1 a crossbar used at the outputs the data belonging to a sector is pending and in Memory can be written.

These memories have different functions. Wear it for one them by appropriate control when registered and Reading to a descrambling (deshuffling) of the tape read signals. Before recording, namely scrambled the digital video signals for possible Faults that otherwise affect an area of the image  focus over a larger part of the picture too distribute and make it appear less disturbing or to be able to cover it better. Another job of Memory consists of compensating for time errors. To do this the signals from the crossbar still with those from mechanical inaccuracies of the magnetic tape device resulting time errors are written into the memory and from the memories in sync with an added studio clock read out.

A third task is the storage of still images, Slow and fast motion playback perceived. At Still image playback will be the last one in memory inscribed image repeated continuously. In slow motion and The magnetic heads do not follow the time-lapse playback Normal speed recorded tracks but sweep the tracks at an acute angle so that on a period with readable signals a period with disturbed signals that follows by scanning the Space between the tracks or two neighboring ones Traces emerge at the same time. In a manner known per se the usable signals can be "collected" in a memory and then in sync with the studio clock be read out.  

Furthermore, EP 0 065 365 B1 is a digital one Known video recorder with a field memory arrangement, the three field memories for storing one each Field of a digital television signal comprises. Of the VCR has a normal playback mode, the the normal motion reproduction of a recorded one digital television signal corresponds, as well as special Playback modes that are slower and faster Motion playback of a recorded digital TV signal. The VCR runs the Field memory arrangement a digital television picture signal at variable speed, the digital TV signal depending on the speed fed either to one or two of the field memories becomes. The digital television signal stored in this way is with one for playback on a television receiver appropriate speed from one or two of the Field memory read out so that none of the Field memory in the same time in which it was read out will be registered. The three Field memory controlled so that it is field frequency be written and read cyclically in a rotating manner. Because of the use of three field memories, this known arrangement also requires a considerable amount Storage overhead.

The present invention has for its object a Storage arrangement for a digital video tape device too create that takes up less space.

This object is achieved in that a digital Memory with the capacity of at least one frame is provided, in which video data read from the tape registered and according to a given sequence read out again that the digital memory in several partial memory is divided and that a switchover of the individual partial memories between writing and reading  all around with a frequency that is much larger than the line frequency is.

The memory arrangement according to the invention has the advantage that less compared to the known memory arrangements Storage space is required, i.e. the circuitry Effort is reduced. All of the above are included Operating modes possible.

Switching the partial memory between writing and Reading is preferably done at pixel frequency. There are however, to lower switching frequencies, for example 1/2 pixel frequency possible.

According to a further development, three partial stores are provided, in which circulating in one of the partial stores within one pixel period data of two consecutive Pixels at two consecutive addresses be written while under two at the same time independent addresses data from the other two Partial memories can be read.  

Here the read / write memory used in the so-called "Page mode" operated, which means a registered mail Video data becomes possible at high speed.

By those listed in the further subclaims Measures are further advantageous developments and Improvements of the invention specified in the main claim possible.

Embodiments of the invention are in the drawing represented with several figures and in the following Description explained in more detail. It shows:

Fig. 1 is a block diagram of the embodiment and

Fig. 2 is a schematic representation of the timing of the write and read operations.

In the memory device of Fig. 1, three sub-memories 1, 2, 3 are provided, whose data inputs are jointly connected to an input 4 of the memory array. The data inputs of the partial memories 1 , 2 , 3 , the input 4 and the data outputs and the output 5 of the memory arrangement each have a width of 16 bits, 8 bits being provided for luminance and 8 bits for chrominance.

The partial memories 1 , 2 , 3 are constructed from known read / write memories, so-called RAMs. For example, the TMS 4164 from Texas Instruments, which has a capacity of 65536 × 1 bit, is suitable.

In order to achieve the width of 16 bits, 16 each Blocks connected in parallel. For one of the pixels capacity corresponding to a full screen 7.5 × 16 blocks required, so that in the illustrated Embodiment of each partial memory 3 × 16 blocks contains a 10-bit address for addressing is required.

The data outputs of the partial memories 1 , 2 , 3 are each connected via a data register 11 , 12 , 13 to inputs of a switching device 10 , the output of which represents output 5 of the memory arrangement.

The address inputs of the partial memories 1 , 2 , 3 are connected to address generators 15 , 16 , 17 via a further switching device 14 . Finally, a changeover switch 18 is provided which cyclically connects one of the write control inputs (W inverted = write enable) to ground potential, as a result of which the partial memory 1 , 2 or 3 concerned is switched over to the write mode.

The switching devices 10 , 14 and the switch 18 are controlled by a three-phase multiplex control device 20 .

The video data supplied to input 4 each contain an 8-bit word luminance and an 8-bit word chrominance in parallel, the chrominance data comprising the components Cr and Cb sequentially. These data, which correspond to two pixels with respect to the luminance, are fed to the data inputs of the partial memories 1 , 2 , 3 and are each written into the partial memory which is in the write mode. According to the page mode operation, the data are written into successive addresses, which takes less time than the writing under two non-successive addresses. This is particularly advantageous because the video data supplied to the memory arrangement are time-compressed due to design-related gaps in the reproduced signals.

The address generators 15 , 16 , 17 generate addresses for writing and reading, which result from the descrambling mentioned at the beginning and from the respectively selected playback speeds. The switchover device 10 is controlled in such a way that a luminance value and the associated chrominance value are fed from a partial memory 1 , 2 , 3 to the output 5 .

In FIG. 2, three strokes of a switching cycle of the memory part 1, 2, 3. In the first cycle, the data of two pixels are written into the partial memory 1 at two successive addresses (for example a / b). During the same cycle, data are read out of the partial memories 2 and 3 - at two independent addresses c and d depending on the requirements of the descrambling and the playback speed.

In the second cycle, data from two further pixels are written into the partial memory 2 and data from the partial memories 3 and 1 are read out. Finally, in the third cycle, partial memory 3 is operated in write mode and partial memories 1 and 2 are operated in read mode.

Claims (6)

1. Storage arrangement for a digital video tape recorder, in which video data are / are recorded on a magnetic tape distributed over several sectors, characterized in that a digital memory with the capacity of at least one frame is provided, in which video data read from the tape is written and according to a predetermined Sequence can be read out again that the digital memory is divided into several partial memories ( 1 , 2 , 3 ) and that the individual partial memories ( 1 , 2 , 3 ) are switched over between writing and reading at a frequency which is substantially greater than that Line frequency is. 2. Storage arrangement according to claim 1, characterized characterized in that the switching with pixel frequency he follows. 3. A memory arrangement according to claim 2, characterized in that three partial memories ( 1 , 2 , 3 ) are provided, in which data of two successive pixels are written continuously into one of the partial memories within one pixel period under two successive addresses, while simultaneously under two independent addresses Data can be read from the other two partial memories. 4. Memory arrangement according to claim 3, characterized in that inputs of a switching device ( 10 ) are connected to outputs of the partial memory ( 1 , 2 , 3 ). 5. Memory arrangement according to claim 4, characterized in that write and read address generators ( 15 , 16 , 17 ) can be connected to address inputs of the partial memory via a further switching device ( 14 ). 6. Memory arrangement according to claim 5, characterized in that the inputs of the partial memories ( 1 , 2 , 3 ) are connected in parallel and can be acted upon with signals which each comprise a data word luminance information and a data word chrominance information in parallel.