JPS6278921A - Signal discriminating method - Google Patents

Abstract

PURPOSE:To discriminate whether or not there is a coded signal exactly with simple constitution by counting the error check detection signal of the coded signal for a specific period. CONSTITUTION:Timing pulses A at intervals of one field are supplied to a counter and a comparing circuit 7, and the resetting of the counter 6 and comparison by the comparing circuit 7 are performed. For example, when an error- free detection signal is obtained C at the terminal part of each block B of playback data, counting operation is carried out by the counter 6 after the 1st timing pulse, and its counted value is compared by the comparing circuit 7 with the next timing pulse, so that when the counted value is within a specific range, a decision output D appears at a terminal 8. Consequently, the possibility that an error is not regarded as an error in an error check as to a video signal and a nonrecording part except a PCM audio signal is extremely small and exact discrimination making is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal discrimination method suitable for use in a magnetic recording/reproducing apparatus that records and reproduces encoded audio signals using, for example, a rotary head.

[Summary of the invention]

The present invention relates to a signal discrimination method for determining the presence or absence of an encoded signal, and enables easy and accurate discrimination by counting detection signals of error checks of encoded signals.

[Conventional technology]

For example, there is a standard called 8mm video tape recorder. According to this standard, recording and reproduction are performed using a pair of rotating heads that are spaced at an angular interval of 180 degrees from each other, and the tape is wound within a range of 221 degrees around the rotational surface of the heads. Video signals are recorded and played back in a 180-degree section of these 221 degrees, and recording and playback of encoded (PCM) and time-axis compressed audio signals are performed in the remaining 36-degree section. It looks like this.

In other words, FIG. 3 shows the format of a recording track on a tape according to the above-mentioned standard. Starting from the right side where the head starts to come into contact with the tape, a plunge part (51) corresponding to 5 degrees of head rotation angle is provided at the leading end. A clock run-in section (52) synchronized with the following PCM data is provided during a period of 2.06 degrees (corresponding to three horizontal periods (H) of the video signal) in the latter half of this entry section (51). This run-in part (5
Following 2), a PCM data portion (53) of the time-axis compressed audio signal is provided over 26.32 degrees. Following this data section (53), the period < 2.06 degrees (3H) is used as a back margin section (54) for recording position deviation during after-recording, and after this, the video section of 2.62 degrees and the PCM data. A guard portion (55) is provided. Following this guard section (55), a video signal section (56) for 1 field is provided over 180 degrees. Furthermore, a separation part (57) of 5 degrees is provided after this.

Therefore, in this standard, the video signal of 1 field is recorded and played back in the video signal section (56), and the audio signal of 1 second during this time is compressed in the time axis to PCM and transmitted to the PC.
The data is recorded and reproduced in the M data section (53). These recording tracks are sequentially provided diagonally in the longitudinal direction of the tape, and continuous video and audio signals are recorded and reproduced.

By the way, in the above-mentioned standard, if 180 degrees of the video signal section (56) is divided into five equal parts, each part becomes 36 degrees. On the other hand, if you add the PCM data section (53), 5 degrees of the entry section (51), 2.06 degrees of the subsequent back margin section (54), and 2.62 degrees of the guard section (55), it is exactly 36 degrees. . Therefore, it has been proposed to form a recording and reproducing apparatus exclusively for audio signals by utilizing the apparatus of the above-mentioned standard.

FIG. 4 shows an example of a recording track format for this purpose. In the figure, the protruding part (
51) to the guard portion (55) is equivalent to the above-mentioned standard, and this section is defined as the first segment. Next, from the starting end side of the conventional video signal section (56), an entry section (61), a run-in section (62), a data section (63), a margin section (64), and a guard section (65) having the same configuration as described above are provided. , this section is defined as the second segment. Furthermore, a video signal section (56
) are repeatedly provided every 36 degrees, and are defined as the third to sixth segments, respectively. After this, a separation part (57) of 5 degrees is provided.

As a result, six segments, first to sixth, are provided. Then, for each of these segments, the rotational angular position of the rotary head is detected, and PCM data is output and recorded at times corresponding to desired segments (sections), each 36 degrees from the opposite end of the head. By doing this and performing reproduction by gating the time of the reproduction signal, each segment can be recorded and reproduced independently.

When re-recording on a tape that has been used once, a so-called flying erase head is used to selectively erase only that section by driving the head only during the time it is in contact with the section of the desired segment. can be erased and re-recorded.

In this way, PCM audio signals can be recorded and played back independently for each section of the tape divided into six sections in the width direction.
For example, by using a tape capable of recording 4 hours, it is possible to record and reproduce PCM audio signals for 24 hours, which is 6 times that amount.

However, in such a device, the PCM audio signal is 6
It may not be recorded in all segments.

Therefore, if the user accidentally selects a segment that has not been recorded and plays it back, there is a risk that the noise will be set to [1] and a large level of noise will be emitted, or that the silence due to muting will continue and be mistaken for a malfunction. There is.

Therefore, it has been proposed to display where in the six segments the PCM audio signal is recorded during playback.

In this case, a method was first considered in which a pilot signal of a specific frequency, for example, 230 kHz, is superimposed and recorded on the PCM audio signal, and this is detected during playback to determine the presence or absence of the PCM audio signal. However, this method requires a special circuit to superimpose the pilot signal during recording, and the installation of such a circuit is optional, so it is difficult to distinguish when playing back a tape on which the pilot signal has not been superimposed. In addition, the frequency that can be used as a pilot signal is close to the chroma component of the video signal, such as the 230 kHz mentioned above, and if the video signal is recorded in the second to sixth segments. There was a risk that this would be erroneously detected.

By the way, in the above-mentioned standard for the 8mm video tape recorder, an error correction code is added to each predetermined amount of data in the PCM audio signal, and a CRC code, for example, for detecting this error is also provided.The present application focuses on this point. The focus was on

[Problem that the invention seeks to solve]

The conventional technology has a problem in that it is not easy to determine the presence or absence of an encoded signal.

[Means for solving problems]

The present invention supplies a signal including an encoded signal to a predetermined error check circuit (5), counts the error check detection signal for a predetermined period (counter (6)) L, and uses this counted value to detect the encoded signal. This is a signal discrimination method in which presence or absence is determined (comparison circuit (7)).

[Function] According to this, the encoded signal is checked for errors and the detected signals are counted for a predetermined period to determine the presence or absence of the encoded signal, so it is possible to easily and accurately encode the encoded signal with a simple configuration. It is possible to determine the presence or absence of a signal.

〔Example〕

FIG. 1 shows an example of a configuration for implementing the method. In this figure, a signal reproduced from a tape (1) by a magnetic head (2) is supplied to a PLL (4) through a reproduction amplifier (3). The reproduced data and self-clock are taken out by this PLL f41, and these signals are supplied to the error check circuit (5).

Here, in the PCM audio signal, an error correction code is used to correct errors during demodulation, and a special
An error check code is provided to output the error check code, and this error check code is added to each block of a predetermined amount of data of the PCM audio signal, for example, as a CRC code.

Therefore, by dividing the reproduced data by the generating polynomial of this CRC code, if the remainder is "0", it is possible to detect no error.

This detection signal is supplied to a counter (6). Then, the pulses of the detection output are counted for a predetermined period of time, and this count value is supplied to a comparator circuit (7), and when this value falls within a predetermined range, a determination output is taken out to a terminal (8).

That is, in the time chart shown in FIG. 2, timing pulses at intervals of one field as shown in A are supplied to the counter (6) and the comparator circuit (7), and the counter (6) is reset and the comparator circuit (7) is reset. ) comparison is made. For example, if an error-free detection signal as shown in Figure C is obtained at the end of each block of reproduced data as shown in Figure B, then the counter (6) starts after the first timing pulse. Counting is performed, and at the next timing pulse, the count value is compared in the comparator circuit (7), and when the value is within a predetermined range, a discrimination output as shown in the figure is taken out to the terminal (8). Ru.

In this way)) CM audio signals are discriminated, but according to the method described above, an error check is performed and the detection signals are counted to make the discrimination, so video signals other than PCM audio signals and unrecorded parts are detected. In this case, the possibility that the error check turns out to be an error is extremely small, and the determination can be made accurately.

Furthermore, there is no need to record Byrondo signals or the like during recording, and the recording can be carried out extremely easily.

Note that the count value of the detection signal is, for example, according to the standard of an 8 mm video tape recorder, a block corresponds to one field.13
2 exists, and this value of 132 is the normal value, but in reality it is necessary to take into account omissions due to noise, etc., and the comparator circuit (
In 7), it is preferable to set the discrimination range to about 132±10%.

[Effects of the Invention] According to the present invention, an error check of an encoded signal is performed,
Since the detection signal is counted for a predetermined period of time to determine the presence or absence of a coded signal, it is now possible to easily and accurately determine the presence or absence of a coded signal with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example for realizing the present invention, FIG. 2 is a diagram for explaining the same, and FIG. 3, FIG. 4 is a diagram for explaining a conventional technique. (5) is an error check circuit, (6) is a counter, (7
) is a comparison circuit.

Claims (1)

[Claims] A signal including the coded signal is supplied to a predetermined error check circuit, the detection signal of this error check is counted for a predetermined period, and the presence or absence of the coded signal is determined based on this counted value. Signal discrimination method.