JPH0748285B2 - Digital playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a digital reproducing apparatus for reproducing a magnetic tape on which an encoded pulse code modulation signal is recorded.

[Conventional technology]

FIG. 3 is a diagram showing a recording format by a conventional pulse code modulation type digital reproducing apparatus disclosed in, for example, Japanese Patent Laid-Open No. 56-37870. 1 is magnetic tape, 16
~ 23 are recording tracks. If a pulse code modulation (hereinafter referred to as PCM) signal sequence that has been analog-digital converted and arranged in time is Dn, this PCM signal sequence Dn is delayed by several blocks (1 unit in the figure) for each track. They are arranged in the array shown in. In recording track 16, D ₁ , D ₇ , ...
An error check code (often a shortened cyclic code CRCC is used) P is added to D ₃₇ , and a synchronization signal S is added to form a frame. The recording tracks 17 to 21 have the same structure. Also, the recording track
At 22, a check symbol Q ₁ , of an error correction code (for example, Reed-Solomon code) added to a predetermined PCM signal string,
An error check code P is added to Q ₃ ... Q ₁₃ and a synchronization signal S is added to form a frame. The recording track 23 is similar to the recording track 22. Also, recording tracks 16-
A collection of each frame of the recording track 23 is called a block.

Next, FIG. 4 shows the arrangement of the PCM signal and the arrangement of the check symbol Q of the correction code in an easily understandable manner. As described above, the temporally arranged PCM signal trains Dn are arranged at a distance of several blocks as shown in the figure. This is called interleaving and has the function of dispersing errors that occur due to scratches or defects on the tape. Further, as will be described later, the PCM signal before editing and the PCM signal after editing are doubled for a certain period near the editing point by using a correction means, the data before editing is faded out, and the data after the editing point is faded in. By doing so, crossfading is possible, and there are also functions such as connecting signals smoothly before and after the edit point.

FIG. 5 is a schematic block diagram of a conventional pulse code modulation type digital reproducing apparatus. In the figure, 24 is an analog signal input terminal, 25 is an analog digital converter (hereinafter referred to as A /
D converter), 26 is an error correction coding circuit (hereinafter, Q
Encoding circuit), 27 is a track distribution circuit, 28 is an interleave circuit, 29 is an error check encoding circuit (hereinafter referred to as P encoding circuit), and 30 is an MFM for recording a PCM signal.
Modulation circuit such as (Modified Frequency Modulation), 31
Is a recording head, 2 is a reproduction head, 3 is a demodulation circuit for demodulating the output reproduced from the reproduction head into a PCM signal, and 4 is a reproduction P
P code check circuit for checking the error check code (hereinafter referred to as P code) in the CM signal, 5 is a de-interleave circuit for restoring the track delayed data to the original, 6 is a multi-track PCM signal arranged in a time series signal Track synthesis circuit, 32
Is a Q code decoding circuit that performs error correction of an error correction code (hereinafter referred to as Q code), 14 is a first edit point detection circuit that detects an edit point based on the detection result of the P code check circuit 4, and 15 is a Q code Second detection of the edit point based on the result of the decoding circuit
Edit point detection circuit, 11 is first and second edit point detection circuits 14 and 15
An edit processing circuit that connects the PCM signal near the edit point without level jump by the control signal from, 12 is a digital analog converter (hereinafter referred to as D / A converter), and 13 is an analog signal output terminal.

Next, the operation of the digital reproducing apparatus will be described.

The analog signal input from the input terminal 24 is the A / D converter 2
Converted to PCM signal by 5. In the Q encoding circuit 26, the check symbol Q is added to this PCM signal sequence Dn. In the track distribution circuit 273 interleave circuit 28, the third
It is converted into the PCM signal array as shown in FIGS.
Further, the P code is added to each track by the P code circuit 29, the synchronizing signal S is further added, and the signal is sent to the modulation circuit 30. The modulation circuit 30 modulates a signal recordable on the magnetic tape and records it on the magnetic tape 1 via the recording head 31.

Next, the operation on the reproducing side will be described. The signal read by the reproduction head 2 is converted into a PCM signal by the demodulation circuit 3, an error is detected by the P code check circuit 4, the de-interleave circuit 5, the track synthesizing circuit 6, and the Q code decoding circuit.
32 error detection and error correction, time-series PCM
Become a signal.

When performing normal reproduction without a hand-cutting editing portion, the PCM signal output from the Q code decoding circuit 32 is the editing processing circuit 11
Is output as it is, converted into an analog signal by the D / A converter 12, and output from the analog signal output terminal 13. In the case of reproducing the manually cut magnetic tape 1, attention is paid to the fact that errors are intensively generated at the same position in the vertical direction of a plurality of recording tracks because the vertical cutting is performed at the editing point. First using code check result
The control output of the edit point detection circuit 14 is sent to the edit processing circuit 11. On the other hand, the Q code is added to the track-delayed PCM signal as shown in FIG. 4. Therefore, if there is a hand-cutting edit point in the code, the content of the code is matched before and after the edit point. The control output of the second edit point detection circuit 15 focusing on the disappearance is similarly sent to the edit processing circuit 11. In the edit processing circuit 11, the edit processing is executed by the control signals from both the first edit point detection circuit 14 and the second edit point detection circuit 15 according to the flow chart of FIG. 6 described later. The output of the edit processing circuit 11 is converted into analog data by the D / A converter 12 and output from the analog signal output terminal 13.

FIG. 6 shows a flow chart for discriminating hand-cutting editing. First, the control signal which is the first edit point detection signal from the first edit point detection circuit 14 is checked (step 1S), and it is judged whether or not the control signal is detected (step S2). , The next edit point detection signal from the second edit point detection circuit 15 is transferred to the check of the control signal (step 3S),
If not detected, the process returns to the check of the control signal from the first edit point detection circuit 14 again. On the other hand, after the processing in step 3S, it is determined whether or not the control signal from the second edit point detection circuit 15 is detected (step 4S), and if detected, the edit processing is started (step 5S). If not detected, the process returns to the start and enters the check of the control signal from the first edit point detection circuit 14.

Since the PCM signal is delayed between the recording tracks near the hand-cutting edit point, a PCM signal before editing and a PCM signal after editing are used near the editing point for a period of time 2
It can be produced in a heavy manner. FIG. 7 shows the reproduced signals before and after the hand-cutting edit point. If the left side of the editing point is A tape and the right side is B tape as shown in FIG. 7 (a), the reproduced signal of this tape can produce an overlapping section of j block as shown in FIG. 7 (b). The playback signal of the A tape is faded out, and the playback signal of the B tape is faded in, so that cross-fading is performed and the level jump of the playback signal can be prevented. The crossfade section j is usually related to the interleave length, and in the interleave of FIG. 4, the relationship of 3l> j is established.

[Problems to be solved by the invention]

Since the conventional digital reproducing apparatus is configured as described above, the Q-code decoding circuit 32 has a function of correcting an error caused by recording / reproducing of the magnetic tape 1 and a code before and after the hand-cut editing point-charging. It is necessary to have a function of detecting that the two become inconsistent (correction addition). In other words, in the former, it is necessary to maximize the ability of the code to perform error correction, and in the latter, it is also necessary to reliably perform uncorrectable detection, and a decoding algorithm is adopted to meet the requirements of the former. Then, there may be a case where the uncorrectable detection cannot be performed for the code that extends over the hand-cutting edit point, and an erroneous correction is made. Conversely, if a decoding algorithm is adopted to satisfy the latter requirement, the uncorrectable Although the detection can be performed reliably, there is a problem that the error correction capability is deteriorated and the normal reproduction is hindered.

The present invention has been made to solve the above problems, and a digital reproducing apparatus capable of performing error correction up to the maximum capacity of a code during reproduction and surely performing edit detection as well. Aim to get.

[Means for solving problems]

A digital reproducing apparatus according to the present invention comprises two kinds of decoding means, a decoding means having a high error correction ability and a decoding means having a high error detection ability, and when an editing point is detected by the first editing point detecting means, A decoding means having a high error detection capability is used.

[Work]

The digital reproducing apparatus according to the present invention comprises two kinds of decoding means, a decoding means having a high error correction ability and a decoding means having a high error detection ability, and an error occurs when the editing point is detected by the first editing point detecting means. By using the decoding means having high detection ability, the error detection ability at the editing point can be improved, while the error correction can be performed with high accuracy at the points other than the editing point.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 7 and 10 are signal selectors, 8 is a first Q code decoding means having a high error correction capability, and 9 is a second Q code decoding means having a high error detection capability. The other blocks that are the same as those shown in FIG.
The duplicate explanation is omitted.

Next, the operation will be described. The signal read from the magnetic tape 1 by the reproducing head 2 is converted into a PCM signal by the demodulation circuit 3 and error-detected by the P code check circuit 4. Further, through the de-interleave circuit 5 and the track synthesizing circuit 6, the first Q code decoding means 8 or the second Q code decoding means 9 selected by the linked signal selectors 7 and 10 perform error detection and error correction. Then, it becomes a time series PCM signal.

In the case of performing normal reproduction without a hand-cut editing portion, the signal selectors 7 and 10 select the first Q code decoding means 8 having a high error correction capability, correct the capacity of the code and output it. The edited PCM signal is output as it is by the edit processing circuit 1, converted into an analog signal by the D / A converter 12, and output from the analog output terminal 13.

In the case of reproducing the magnetic tape 1 edited by hand cutting, the signal selectors 7 and 10 are switched by the control signal of the first edit point detection circuit 14 using the P code check result, and the second error detection capability is high. Q code decoding means 9 is selected. Since the second Q code decoding means 9 has a high error detection capability,
When there is a hand-cutting edit point in the code, it is detected that the code does not match before and after the edit point. That is, the uncorrectability is surely detected. Then, the second edit point detection circuit 15 judges whether or not the uncorrectable state is over several blocks, and if it is over several blocks, the edit processing is performed and the control signal is sent to the edit processing circuit 11. Editing processing circuit
In 11, edit processing is executed by the control signal from the second edit point detection circuit 15. The output of the editing processing circuit 11 is the D / A converter 1
Converted to analog data by 2 and analog output terminal 1
It is output from 3.

FIG. 2 shows a flow chart of the above-mentioned cut-off editing judgment processing. According to this, first, the control signal which is the first edit point detection signal from the first edit point detection circuit 14 is checked (step 11S), and it is judged whether or not the control signal is detected (step 12).
S), if detected, switch to second Q code decoding means 9 (step 13S); if not detected, first Q
The first edit point detection circuit is again provided with the code decoding means 8 as it is.
Return to the check of control signal from 14 (step 14S).
On the other hand, the second Q code decoding means 9 is activated to check the control signal from the second edit point detection circuit 15 (step 15).
S), it is judged whether or not the control signal is detected (step 16S), and if detected, the editing process is started (step 17S),
If not detected, the process returns to the start and enters the check of the control signal from the first edit point detection circuit 14.

The first edit point detection circuit 14 detects the control signal,
Even though the Q code decoding means 9 is selected,
If the edit point detection circuit 15 determines that the control signal is not detected, the error correction capability will be reduced despite the fact that the edit process is not performed and normal reproduction is performed, but it is only a moment in time, and overall Judging from the ratio, it does not matter.

Although two types of decoding circuits, the first Q code decoding means 8 and the second Q code decoding means 9, are used in the above embodiment,
When using a program-controlled decoding circuit, the amount of hardware is the same if the decoding algorithm program with high error correction capability and the decoding algorithm program with high error detection capability are switched and used. (There is one type of decoding circuit), and the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, when two types of decoding means, that is, a decoding means having a high error correction ability and a decoding means having a high error detection ability are provided, and the editing point is detected by the first editing point detecting means Since the decoding means having a high error detection capability is used, the error detection capability at the editing point is improved, and as a result, an error can be reliably detected at the editing point.

[Brief description of drawings]

FIG. 1 is a block diagram showing a reproducing side of a digital reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a flow chart showing a hand-cut editing judgment processing according to an embodiment of the present invention, and FIG. 3 is a conventional recording. FIG. 4 is a track pattern diagram showing the format, FIG. 4 is a track pattern diagram showing the interleave of the conventional PCM signal, FIG. 5 is a block diagram showing the conventional digital reproducing device, and FIG. FIG. 7 is a flow chart, which is an explanatory view showing the cross-fading relation of signals in the conventional edit processing circuit. 1 is a magnetic tape, 4 is a P code check circuit, 7 and 10 are signal selectors, 8 is a first Q code decoding means, and 9 is a second Q code.
Code decoding means, 11 is an edit processing circuit, 14 is a first edit point detection circuit, 15 is a second edit point detection circuit, and 16 to 23 are recording tracks. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 60-52964 (JP, A) JP 60-51176 (JP, B1) JP 61-23594 (JP, B1)

Claims (4)

[Claims] 1. A digital reproducing apparatus for reproducing a recording medium having digital data added with the first error code after interleaving the data added with the second error code, and reproducing from the recording medium. First edit point detecting means for detecting the presence / absence of edit points of the digital data, first decoding means for decoding the digital data based on the first error code, and first decoding means Second decoding means for decoding the digital data based on the second error code; second editing point detecting means for detecting the presence or absence of an editing point of the digital data in the decoding processing by the second decoding means; When the second edit point detecting means receives the information indicating that the edit point is detected, it operates for a predetermined period,
Edit processing means for processing the data before and after the edit point of the digital data decoded and deinterleaved by the second decoding means so as to be connected without level jump;
The second decoding means includes two types of decoding means, a decoding means having a relatively high error correction ability and a decoding means having a high error detection ability, and the editing point is detected by the first editing point detecting means. In this case, the digital reproducing apparatus is characterized in that it is configured to use a decoding means having a high error detection capability. 2. The first edit point detecting means edits the detected position when a concentrated error is detected at substantially the same vertical position of a plurality of recording tracks formed on the recording medium. The digital reproducing device according to claim 1, wherein the digital reproducing device is determined as a point. 3. The second edit point detecting means determines the detection point as an edit point when an undecodable area is continuously detected for a predetermined period in the decoding processing by the second decoding means. The digital reproducing apparatus according to claim 1, wherein 4. The second decoding means comprises a program control type decoding circuit, and comprises two kinds of programs, a decoding program having a high error correction capability and a decoding program having a high error detection capability. The digital reproducing apparatus according to claim 1, wherein the digital reproducing apparatus is a digital reproducing apparatus.