JPS6367274B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital signal recording and reproducing apparatus that can prevent information from being lost at editing points when editing a tape on which digital signals are recorded.

Conventionally, when editing tapes on which digital signals have been recorded, applying the editing method of cutting the tape diagonally and splicing it together, which was done with conventional analog recorders, poses various problems. . That is, omissions and discontinuities in digital data at editing connection points are audibly reproduced as clicking sounds, and data error sections may vary depending on the accuracy and skill level of the editing work. Electronic editing methods have been developed to overcome the above-mentioned drawbacks. According to this method, for example, two types of tapes to be connected (when connecting parts of one tape, this is done after dubbing one part to another tape), respectively, by sending a control signal such as a time code to each tape. Run synchronously based on. At this time, the tapes to be spliced run in playback mode, and the tapes to be spliced shift from playback mode to record mode at a predetermined editing point, and are edited into one tape. The above are conventional electronic editing methods used for editing video tapes. A recording format as shown in FIG. 1 has been proposed as a method for applying this electronic editing method to editing digitally recorded tapes and preventing data loss at editing points. In other words, by dividing the data into blocks B of appropriate length and compressing the data portion, a blanking interval of an appropriate length is created for each block.
This is a method in which a BK is provided and mode switching from playback to recording and from recording to playback is performed in this blanking section BK. In the figure, F indicates one frame section,
F _D1 , F _D2 ... represent the first data frame, second data frame ..., F _P1 , F _P2 ... represent the first parity frame, second parity frame, etc. DP is the data,
It shows the parity frame section. The length of this blanking section corresponds in time to the wow and flutter of the two recorders, the time it takes to establish frame synchronization, and the like. This method has a major drawback in that the recording frequency becomes higher than necessary due to the detection of the blanking section BK and the data compression, that is, the recording wavelength becomes shorter. On the other hand, in conventional recording formats that do not provide blanking sections, data is continuous, so data errors inevitably occur at mode switching points (editing points), and playback with the same click feeling as when editing by cutting the tape is inevitable. It will be done.

The present invention provides a digital signal recording and reproducing apparatus that eliminates the above-mentioned drawbacks and can prevent data errors at editing connection points without providing blanking sections. Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent drawings.

FIG. 2 shows a recording format of a magnetic tape in an apparatus according to an embodiment of the present invention. In this embodiment, data is distributed to four tracks #1 to #4 on the tape, and each track constitutes a frame. One frame of data consists of a frame synchronization pattern S followed by a data word D.
D They are arranged in order starting from ₁ . A cyclic code CRC for error detection is added to the end of the data frame. Furthermore, the first and sixth frames of data
Parity words generated for each corresponding data word of a frame are arranged separately from the data frames. The parity word frame is a frame different from the data word frame, in which parity words P are arranged in order from _P1 with a synchronization pattern S' at the beginning, and a cyclic code is placed at the end of the frame.
CRC is added. In the above example, when the number of frames of the data word is 10, the number of frames of the parity word is 5, and one block consists of a total of 15 frames.

Next, a method of error detection and correction when using the recording format of this embodiment will be explained below. Focusing on any one track of the recording format shown in FIG. 2, if an error occurs in a data word or parity word in one frame, error detection is performed using a cyclic code CRC added to the end of the frame.

On the other hand, parity words are generated from data words that are five frames apart from each other. That is, for example, since P _1-4 = D _1-4 D _6-4 ,
If an error occurs in D _1-4 , the error is detected by the cyclic code CRC of the frame including D _1-4 , and then P _1-4 ,
If there is no error in the frame containing D _6-4 , D _1-4 becomes P _1-4
D _1-4 is completely corrected by inverting the bit in which the error was detected in D _6-4 . As described above, even if an error occurs in either one of the two data words that generate parity, the erroneous data word is completely corrected by the generated parity word and the other data word. Furthermore, the above two data words and parity words can be placed at arbitrarily large distances on the tape (5 frames in this embodiment), so even if a burst dropout occurs, the parity word The probability of a situation in which it is impossible to correct simultaneous errors in the words constituting the word can be kept extremely low.

Next, we will discuss the case where electronic editing is performed.

When electronically editing a tape using the recording format described above, if editing connection is possible only in the section of the parity frame group described above, it is possible to prevent the data itself from being lost at the editing connection point. . In other words, in the example of FIG. 3, when data after D ₃ of the recorded tape to be edited is deleted and data after D ₃ ' is to be inserted in its place, the parity frame group P ₃ of the block containing D ₃ is deleted. When the recording head passes over the recording head, recording of the data to be recorded after _D3 ' is started. At this time, the tape recorder's wah
Errors occur in editing points due to flutter and other factors, but according to the present invention, the temporal length of a parity frame group can be set arbitrarily by changing the number of data frames that make up one block. It is possible to provide sufficient margin for errors in editing points. Therefore, the necessary data, D ₂ in the case of Figure 3, will not be deleted by mistake. In addition, if the parity frame group _P3 that remains erased is within one frame, it is judged as an error by CRC, and 1
Even if the number of parity frames exceeds the number of frames, there will be a predetermined number of parity frames for the next P ₃ ', so malfunctions can be prevented by providing a protection circuit that counts the number of parity frames.

Next, FIG. 4 shows a schematic configuration of a digital signal recording and reproducing apparatus of this embodiment for recording and reproducing the tape shown in FIG. 2.

A digital signal input to an input terminal 1 is distributed by a rearrangement circuit 2 according to the number of recording tracks. The compression memory 3 compresses the recorded data on the time axis and stores the frame synchronization pattern, cyclic code CRC,
Provide a time gap in which parity words can be interpolated.
A parity word generator 4 generates a parity word from the signal delayed by the memory 5 for a certain period of time and the output signal from the compression memory 3. A mixer 7 selects the output of the parity word generator 4 and the data word further delayed by the delay memory 6, and inserts it into a predetermined position. A cyclic code generator 8 generates a cyclic code CRC for input signals of data words and parity words for one frame, and a mixer 9 interpolates it at the end of each frame. The synchronization pattern S of the data frame is generated by a synchronization pattern generator 10, and the synchronization pattern S' of the parity frame S' is generated by a synchronization pattern generator 11, which is switched by a switch 12 and is generated by a mixer 9 to generate a predetermined signal of a predetermined frame. is interpolated at the position of A gate circuit 13 outputs the obtained recording signal series to the recording signal output terminal 14 based on the command from the recording command circuit 24. Thereafter, the data is subjected to appropriate recording modulation and recorded on the magnetic tape via a recording amplifier and a head, but this is omitted from the drawing.
On the other hand, in the reproducing system, recorded data on the magnetic tape is read out by a reproducing head, amplified, waveform-shaped, demodulated by a demodulation circuit, and applied to a terminal 15, but this is omitted in the drawing. The demodulated digital data is separated into frame synchronization signals S and S' by a frame synchronization signal separation circuit 16, and a jitter absorption memory 17 eliminates time axis fluctuations due to wow and flutter caused by the tape running of the digital data. Absorb. The memories 18 and 19 are provided to align the time phases of the data word that generated the parity word and the parity word in order to perform error correction. The error detection/correction/correction circuit 20 performs operations such as error detection by checking the cyclic code CRC, bit-by-bit error detection and correction using the parity word, and average value interpolation when an uncorrectable error occurs.
Furthermore, in the expansion memory 21, frame synchronization, cyclic code
CRC and parity word parts are removed to extend the time axis of the data word. The rearranging circuit 22 reorganizes the data words into one system and sends them to the output terminal 23.
Output to. Terminal 25 is a recording command input terminal to which recording start or end information is applied, but in recording command circuit 24, the gate circuit is activated only when frame synchronization signal S' of a parity frame is detected by frame synchronization signal separation circuit 16. 13, commands to start and end recording are output. If the recording head and the playback head are placed apart from each other, after the parity frame group is detected (S' is detected) at the playback head, the recording head is moved back to the recording head after a certain time delay due to tape running. Since the parity frame group is located at the top, in this case, the recording command circuit 24 is also provided with a function to delay the recording start and end commands by the tape running time from the playback head to the recording head, so that the parity frame group is always It is now possible to start and stop recording from above. Further, 26 is a clock pulse generation circuit that controls the recording circuits 2 to 13, and by synchronizing the clock pulse that controls the block configuration with the parity frame synchronization signal S' separated from the reproduced digital signal, The configuration of the signal series to be recorded can be made the same as the already recorded signal series. That is, when a parity frame group arrives on the recording head, it is possible to record a recording signal sequence starting from the parity frame group.

As explained above, according to the digital signal recording and reproducing apparatus of the present invention, when editing a recording medium on which digital signals are recorded, it is possible to electronically edit a recording medium on which digital signals are recorded without causing signal dropouts or errors at connection points. becomes possible. Furthermore, since there is no need to provide a blanking section for editing connections, it is possible to reduce the redundancy of digital signals, and therefore relatively high-density recording is possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a recording format of a digital signal on a conventional magnetic tape, FIG. 2 is a diagram showing a recording format of a magnetic tape used in a digital signal recording/reproducing apparatus according to an embodiment of the present invention, and FIG. FIG. 4 is a diagram for explaining an electronic editing method using the recording and reproducing apparatus of this embodiment, and is a diagram showing a schematic configuration of the recording and reproducing apparatus of this embodiment. S, S'...Synchronization signal, P...Parity check code, CRC...Cyclic code, 3...Compression memory, 4
... Parity word generator, 8 ... Cyclic code generator, 10, 11 ... Synchronization pattern generator, 16 ...
. . . Frame synchronization signal separation circuit, 20 . . . Correction correction circuit, 21 . . . Expansion memory.

Claims (1)

[Scope of Claims] 1. A data frame composed of digital data divided into a certain number, a first synchronization signal, and an error detection code of the divided digital data, and a plurality of divided digital data. A digital signal that records and reproduces, on a recording medium, a digital signal in which a block is composed of one or more types of parity check codes generated by a combination of data, a second synchronization signal, and a parity frame made up of the parity check code. In a signal recording and reproducing device,
When another digital signal having the block structure is further recorded on a part of the track on which the digital signal having the block structure has been recorded in advance, at least one type of the above-mentioned parity of the blocks of the digital signal recorded in advance is recorded. 1. A digital signal recording/reproducing device characterized in that recording can be started and ended only in a recording medium section in which a group of T frames are recorded. 2. A digital signal recording and reproducing apparatus according to claim 1, characterized in that recording starts from the first bit of a block constituting the digital signal and ends at the last bit of the block. . 3. A reproducing head and a recording head are arranged in order along the running direction of the recording medium, and the reproducing head reproduces a pre-recorded digital signal, and at least one type of blocks constituting the reproduced digital signal. A detection signal is obtained by detecting a group of parity frames, and the detection signal is delayed by the time required for the recording medium to travel the distance between the reproduction head and the recording head, so that the parity frame group is detected by the recording head. 2. The digital signal recording and reproducing apparatus according to claim 1, wherein information for detecting that a position has been reached is obtained.