JP2770307B2 - Error counting method for digital data recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital data recording / reproducing apparatus capable of recording or reproducing image information using digital data. It relates to an error counting method for detecting.

[Summary of the Invention]

The error counting method in the digital data recording / reproducing apparatus of the present invention is based on the identification signal and the error flag signal for the data output from the first decoder for decoding digital data reproduced from a magnetic tape or the like. After making sure that the correct data is detected and counting the number of detected data over a certain period (time),
Since an accurate error rate can be displayed by the calculation, the error rate can be accurately detected even for specific data generated in the entire recording / reproducing system.

[Conventional technology]

In the case of a digital recording / reproducing apparatus capable of recording or reproducing a large amount of information converted into a digital signal on a magnetic tape or a magnetic medium, the information is usually recorded on the magnetic medium or from the magnetic medium. When reproducing information, it is unavoidable to generate error data due to tape noise, dropout, head clock, and the like.

Such error data can be corrected by an error collector provided in the data signal processing circuit if the number of error data is equal to or less than a predetermined value. The reliability of the received information decreases rapidly, for example, in the case of image data and audio data,
This leads to a decrease in image quality or sound quality.

Therefore, a digital recording / reproducing device has been developed which has a function of counting error data during reproduction and informs a user of whether or not the device is operating normally by detecting an error rate. ing.

FIG. 4 shows an outline of a block diagram of a reproducing system in a digital magnetic recording / reproducing apparatus capable of recording and reproducing video information on a magnetic tape with a digital signal, wherein 1 is a pair of recording heads A _1. A drum provided with B ₁ (A ₂ · B ₂ ) and a pair of heads C ₁ · D ₁ (C ₂ · D ₂ ) for reproduction, and at the time of reproduction with respect to the longitudinal direction of the wound tape T. A video signal or an audio signal recorded as a digital signal can be reproduced from the inclined track.

When the recording information is a video signal, for example, FIG.
As shown in FIG. 5, the effective image of one field is divided into 5 segments (6 segments in the PAL system) every 50 lines, and the image data converted into the digital signal of the first segment is shown in FIG. 5 (b). In this manner, the video data is divided into four video sectors, and recorded. (Sector array full) Therefore, if the image data of each segment is recorded in the same manner as above, the screen of one field has 10 tracks (PAL
In 12 tracks).

A preamble and postamble signals D _P1 and D _P2 are added to the leading and trailing ends of each video sector as synchronization and identification signals, and the data in the video sector is divided into, for example, 160 blocks. And the synchronization signal and the identification signal (ID) as described later in the data of each block.
Is added.

Note that in FIG. 5 _{(b), a 1, a} 2, a 3, consisting of a ₄ sectors indicates a range in which the 4-channel audio data is recorded only to mutually interleaved by compressing the time axis, this The data in the sector of the audio track is also divided into five block data like the video data, and each of them is recorded with a synchronization signal and an ID signal added thereto.

Hereinafter, a reproduction system for recording data having such a track pattern will be described.

Reference numeral 2 denotes a reproduction amplifier having an equalizer characteristic, and 3 denotes a waveform shaping circuit for shaping the reproduced digital signal into a pulse signal.

Reference numeral 4 denotes a data separation circuit for extracting a synchronization signal, an identification signal, data, and the like from the waveform-shaped digital signal. Reference numeral 5 denotes an inner decoder for performing signal processing of inner block data as described later. At the same time as error data is corrected by an error correction code in block units, an error flag is added to the error data, and the error data is transmitted to the next frame memory together with an ID signal. In the frame memory 6, the inner block data is written at a predetermined address set by the ID signal, and the deshuffled data read from the frame memory 6 is further converted by the outer decoder 7 into an uncorrected code to which an error flag is added. On the other hand, error correction is further performed, and separated into a luminance signal component and a chrominance signal component by a deline shuffle and a demultiplexer.
After being converted into a binary code by 1: 1 demapping, it is supplied to the concealment circuit 8. Then, the data for which the error correction has not been performed is corrected and output via the A / D converter 9.

Reference numeral 10 denotes an audio-system signal processing unit, the detailed description of which is omitted, but the audio signal returned to an analog signal with the same data error correction and deshuffling functions as the video system is converted to an A / D converter. It has been made available from 11.

Reference numeral 12 denotes a TBC (time axis correction circuit) that can be attached depending on the model.

Note that, in practice, signal processing is performed by a signal flow of four channels in both the video system and the audio system.

Such a digital video signal recording / reproducing device (hereinafter, DV)
TR) is to make the component video signal symmetric
・ When conforming to 2.2 standard, the luminance signal is
The 13.5 MHz sample frequency and the color difference signal are sampled at a sample frequency of 6.75 MHz, and are converted into digital signals by an 8-bit binary code.

[Problems to be solved by the invention]

As described above, the characteristic evaluation of the recording / reproducing system in the DVTR usually requires only detecting the error rate of the reproduced video data. The error flag in the outer decoder 7 to be processed is counted by the error counter 13 and the display unit 14 displays the error rate to the user.

However, the output data of the outer decoder 7 has already been corrected for the error code in the inner decoder 5 and the outer decoder 7. For example, when the characteristics of the recording tape and the characteristics of the head are evaluated, it is not proper. I can't say.

Therefore, it is conceivable to calculate the error rate by counting the error flags in the inner decoder 5 in which the recording characteristics of the magnetic tape or the magnetic head are well reflected.
However, when dropout or head frog occurs, or when variable playback is performed, the synchronization position of block data processed by the inner decoder 5 may not be constant or a synchronization signal may be missing. Therefore, there is a problem that the counting timing of the error code is uncertain and a large error occurs in the measured value.

Further, when counting the error rate of data reproduced by a specific head from a plurality of heads, it is necessary to consider a period during which the head is not in contact with the tape, and it is actually extremely difficult to detect the error rate. become.

Further, when it is desired to know the error rate at the time of variable speed reproduction, the data rate is ±
Since it changes by 30%, the synchronization interval also changes, and the jitter of the drum also causes an error, and it is extremely difficult to calculate an accurate error rate by counting the error flag output from the inner decoder for a certain period.

[Means for solving the problem]

The present invention has been made in view of such a problem,
For example, the inner decoder first extracts the ID signal added to the data divided into blocks every predetermined number, and
ID signal and discriminating means for judging when both of the data in the block are correct data, counting means for counting the judgment result obtained from this discriminating section for a certain section or for a certain time are provided. An arithmetic unit for calculating an error rate based on the count value and the number of data in a certain period when there is no error is provided.

[Action]

Counts the correct number of data output from the inner decoder by referring to the ID signal added to the block of data and the error flag output when an error occurs in the data in the block With this configuration, it is possible to accurately calculate the error rate with respect to the fluctuation or lack of the synchronization signal generated at the time of dropout, bit slip, and variable speed reproduction.

〔Example〕

FIG. 1 is a block diagram showing the detection of an error rate in a digital recording / reproducing apparatus according to an embodiment of the present invention. Reference numerals 21 and 22 denote digital data detected from a tape or the like and an internal signal to which a synchronization signal is input. Reference numeral 22 denotes an ID detection unit for detecting an ID signal as described later in the inner decoder. The ID detecting section 22 can be omitted when it is detected by the data separation circuit 4 described above.

The inner decoder 21 corrects and outputs erroneous data that can be corrected, and transmits uncorrected data together with a specific error flag signal, and is recorded in the next frame memory 23 together with an ID signal.

Then, the data is further corrected by the outer code.

Reference numeral 24 denotes a circuit for determining an error flag output from the inner decoder 21 and data to which an ID signal and a synchronization signal extracted by the ID detection unit 22 are input.
When the ID signal is correctly detected and the data in the synchronous block is correct, an enable signal is supplied to the counter 25 to detect the correct number of data in the reproduced data.

26 is a count holding circuit for holding the count value of the counter 25, 27 is an error rate calculation unit, and 28 is an error rate display unit.

Numeral 29 denotes an error counter control unit for outputting a reset signal for designating the count period of the counter 25 and a latch signal for holding the count value in accordance with the reset signal, and simultaneously calculating an error rate according to the count period. A signal for updating the contents of the section 27 is output so that the error rate for specific reproduction data recorded on the tape can be displayed.

Therefore, the error counter control unit 29, a signal indicating the first and the select signals S ₁ to specify whether to display the error rate of any part of the recorded data, the position of the track sectors of the select data, for example, the frame signal,
The top signal of the designated segment, the top signal of the designated track, and the like are input, and these signals output the reset timing of the counter 25, the latch time of the count holding circuit 26, and the calculation command of the error rate calculation unit 27.

Incidentally, the determination circuit 24 is determined by a positive or false error flag signal data in the sync block corresponding to the ID signal a second select signal S ₂ is inputted to specify the symmetry of the discrimination data, For example, the symmetry of the error data to be detected by the selection of the rotating head being reproduced (Confide-nt Head / Advance Head), the selection of data (Video / Audio), the selection of the error flag (before / after correction), etc. You can choose.

The error counting method of the present invention has the above-described circuit function, detects only correct data from specific data in a specific track among data reproduced from a tape, and calculates an error rate. be able to.

That is, as shown in FIG. 5 (b), for example, the first
If it is desired to know the error rate of the data recorded on the video track in the field, a video select signal is input to the error counter control unit 29.

Then, a reset signal for resetting, for example, every one video sector period is supplied to the counter 25 from the error counter control unit 29, and the value counted for each reset by the counter 25 is latched by the count holding circuit 26, and the error rate is reset. The data is transferred to the calculation unit 27.

Further, by supplying the video data selection signal to the discrimination circuit 24, for example, control is performed so that the ID signal recorded in the video sector is discriminated symmetrically.

This ID signal is, for example, as shown in FIG. 2, added in a minimum block unit obtained by dividing a predetermined number of code data recorded on the tape, and the first two bytes indicate a synchronization signal SNYC. , Followed by the next 4 bytes
60 + 60 bytes and a recording data D _a of, ID signal for identifying the check code byte D _c 4 + 4 bytes is added.

The ID signal includes field numbers (0 to 3),
Segment number (0-4) ｛However, 0 in case of PAL system
~ 5｝, sector number (0-3), block number (0-15)
9) {However, in the case of audio data, 0 to 4} are recorded as address data.

Therefore, the ID of the error data corresponding to the determination circuit 24
Signal, that is, ID indicating the video sector of the first field
If a signal is input and there is no error flag at the synchronous position of this signal, correct data is assumed to have been reproduced, and an enable signal is supplied to the counter 25. And
Only the correct number of data in the video track of the first field can be counted sequentially.

Note that 160 pieces of this block-unit data (also referred to as inner block data) are written in one video sector, so that when counting the correct number of data, the number of data counts becomes considerable.

Thus, the counter 25 is controlled to be reset, for example, for each video segment or for each field, and correct data for each segment or field is sent from the count holding circuit 26 to the error rate calculation unit 27. The correct data for 5 segments (for 1 field) or 60 fields is detected by adding in the transmission error rate calculation unit, and is compared with the correct number of data for 1 field or 60 fields set in advance. This calculates the error rate.
Then, the error rate is displayed on the display unit 28.

It is preferable that the data is smoothed (averaged) within the period constituted by the error rate calculation unit 27 and output to the display unit 28 in order to eliminate the flicker of the display contents.

Thus, the count value of the counter 25 is, for example, as shown in FIG. 3, when the corresponding ID signal is correct and there is no error flag, the count value Q updates the correct number of data. As shown in the period T _0, when the correct ID signal is detected but the error flag signal _SEF is present, or when the correct ID signal is not detected (in this case, the data is also incorrect), the count value Q is n
Next, when there is no correct ID signal and no error flag, the count value Q increases to n + 1 and n + 2.

When calculating the error rate of the audio data for four channels in FIG.
Of the select signal S ₂ selects the ID signal indicating the audio data, the first select signal of the error counter control unit 29 selects, for example, as a playback period of the audio sector. Only when the block unit ID signal indicating the audio data is correctly reproduced and supplied and the error flag signal of the audio block data is correct (indicating no error), the counter 25 is output.
The count value is incremented.

The error rate calculator 27 compares the correct number of data expected to be obtained within a fixed time until the counter 25 is reset or an integral multiple thereof with the count value of the counter 25 counted within the same period. To calculate the error rate.

〔The invention's effect〕

As described above, the error rate counting method of the present invention detects an ID signal of block data and determines whether or not the data in the block is correct based on the ID signal by an error flag, and determines that the data is correct. Is controlled so that the count value of the counter advances only when the synchronization signal is lost, so that the counting operation can be performed even when the synchronization signal is missing and the originally expected synchronization position is unknown,
In particular, the error rate can be evaluated even during variable speed reproduction. Further, since the data error is determined based on the ID signal, the data targeted for the error rate can be individually evaluated, and errors are detected and counted from the output data of the inner decoder. Therefore, there is an effect that the characteristics of the tape and the head, and the error rate caused by the recording / reproducing system device can be comprehensively evaluated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a reproducing system showing an error counting method according to the present invention, and FIG. 2 is a synchronizing signal and I which constitute a block unit.
FIG. 3 is a signal waveform diagram for explaining a data count operation, FIG. 4 is a block diagram of a reproducing system of a digital data recording / reproducing apparatus, and FIGS. 5 (a) and 5 (b). () Is an explanatory diagram showing a field screen and a track pattern of the image data. In the figure, reference numeral 24 denotes a discriminating circuit, 25 denotes a counter, 26 denotes a count holding circuit, and 27 denotes an error rate calculator.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI G11B 20/18 574 G11B 20/18 574H (58) Investigated field (Int.Cl. ⁶ , DB name) G11B 20/18

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein code data obtained by converting the recording information into a digital signal obtained by performing error correction coding is divided into blocks each of a predetermined number, and block data to which an identification code and a check code are added is recorded. In a digital data recording / reproducing apparatus which performs error correction on reproduced array data and rearranges data based on the identification signal to obtain a reproduction signal, the identification signal reproduced from a recording medium and the error Discriminating means for detecting whether or not there is an error in the block data by referring to an error flag obtained at the time of decoding of the correction; and counting the output over a certain period when the discriminating means does not detect an error in the data. An error rate based on the number of data when there is no error signal within the predetermined period and the count value of the count means. Error counting method of the digital data recording and reproducing apparatus characterized by and a calculating means for calculating a. 2. A digital device according to claim 1, wherein said discriminating means is controlled so as to discriminate only the correctness of the block data added to the selected identification signal. Error counting method for data recording / reproducing devices.