JPH04282983A - Digital signal recording method - Google Patents

Abstract

PURPOSE:To make an error correction capability of a video signal and that of an audio signal equal to each other by recording a digital audio signal with an error check code added thereto superimposingly onto a digital video signal with an error check code added thereto. CONSTITUTION:A video signal and an audio signal inputted from input terminals 8, 5 are converted into a digital signal respectively by A/D converters 9, 6 and compressed to a prescribed rate by high efficiency coders 31, 32. Then the result is subjected to error correction coding by error correction coders 33, 34, the signals are superimposed on each other by a mix format circuit 35 and the result is sent to a modulator 36 and a data subjected to digital modulation is recorded onto a tape 1 by a magnetic head 40 through a recording amplifier 37 and a changeover switch 38. Thus, the error correction capability of the video signal is made almost equal to that of the audio signal and since it is not required to provide an area on which the audio signal only is recorded, the redundancy is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital recording method for adding an error correction code to a digital video signal, one or more channels of digital audio signals, and a digital video signal and recording them on a recording medium.

0002

2. Description of the Related Art When a video signal and an audio signal are recorded on a tape for a video tape recorder (VTR) using a rotating magnetic head, the tape has a higher error correction ability for burst errors in the tape running direction. Furthermore, the present inventors have proposed the following method as a digital signal recording method that can obtain a recording format that allows efficient use of tape without increasing redundancy.

In other words, the audio signal recorded on a portion of all the tracks is recorded on a certain n track (n is 2 or more) out of m tracks (m is an integer of 3 or more) making up one field of video signal. , where m>n), and at least odd-numbered samples and even-numbered samples are separated into separate tracks and recorded while being dispersed in the tape width direction.

Therefore, by increasing the number of audio sectors per field, the length of the audio sector can be increased to improve the data error correction ability, and by distributing the n sectors in the tape width direction, the audio signal can be Since odd and even samples are recorded separately, even if a burst error occurs in the tape running direction due to head clogging, half of the data can be secured, improving error correction ability. In addition, redundancy during recording does not increase.

As an example of this, a case will be described in which a four-channel digital audio signal is recorded on a VTR tape.

FIG. 7 is a schematic diagram of a recording format on a tape in a digital signal recording method. 1 is a tape for VTR, 2 is a video sector where video signals are recorded,
Reference numeral 3 indicates an audio sector at the upper end of the tape where audio signals are recorded, and 4 indicates an audio sector at the lower end of the tape where audio signals are recorded. On the tape 1, two tracks constitute one segment, and signals are simultaneously recorded on the two tracks of the same segment. Also, 1 field is composed of 3 segments, and 6 segments (=12
tracks) make up one frame.

[0007] As a device for recording signals on the tape 1, for example, a device as shown in FIG. 8 can be used. When recording a signal, the audio signal input from the audio signal input terminal 5 is converted into a digital signal by the A/D converter 6, and then subjected to processing such as error correction encoding in the audio signal processing circuit 7. 11. On the other hand, a video signal input from a video signal input terminal 8 is converted into a digital signal by an A/D converter 9, and then subjected to processing such as error correction encoding in a video signal processing circuit 10, and then sent to a mixing circuit 11. input.

After mixing the video signal and the audio signal in the mixing circuit 11, the mixed signal is modulated in the modulation circuit 12, amplified by the recording amplifier 13, and then output by the recording head 14 mounted on the rotating drum 20. Record in a segment. Further, in the segment adjacent to this, the signal mixed in the mixing circuit 11 is modulated in the modulation circuit B15, amplified by the recording amplifier 16, and then recorded by the recording head 17. By repeating this operation alternately, signals are continuously recorded on the tape 1.

FIG. 9 is a diagram showing the timing of recording signals onto the tape 1 in the prior art. The audio sector is arranged at the end of one of two adjacent fields in one frame and at the beginning of the other, and audio signals are recorded before and after the boundary between each field. The number of audio signal samples recorded in one field is 48,000/60=800, assuming the sampling frequency is 48kHz and the video signal field frequency is 60Hz.
It is. Since there is one audio sector per field, an audio signal of 800 samples per channel is recorded in one audio sector.

FIG. 10 is a diagram showing the allocation of recording channels in the audio sector. The audio sector is actually divided into two parts by a gap, so it is divided into four parts. Therefore, signals of different recording channels are recorded in four parts. Further, odd-numbered (odd) data is recorded in audio sector 3 at the top of the tape, and even-numbered (even) data is recorded in audio sector 4 at the bottom of the tape. Even if data is lost due to a burst error, at least half of the data is secured and error correction is possible. Also, one audio sector 3
In this case, a channel (hereinafter referred to as CH) is placed on the video sector 2 side.
)1 and CH3 data are recorded, and CH2 and CH4 data are recorded on the tape end side, but in the other audio sector 4, CH2 and CH4 data are recorded on the video track side. , CH on the tape end side
1 and CH3 data are recorded. With this process, even if a burst error occurs at both ends of the tape 1, if the error is within a certain width, half of the data can be secured and error correction can be performed.

FIG. 11 is a diagram showing a data structure within an audio sector in a conventional example. 2 due to gap
Each audio sector is divided into #0 to #2.
It consists of 30 data blocks up to 9. Furthermore, a synchronization signal (Sync.
) The block address, ID, parity, data, inner code C1, and outer code C2 are recorded in the format shown in the figure. In the 80 bytes between the parity and the inner code C1, data is recorded in blocks #0 to #19, and outer code C2 is recorded in blocks #20 to #29.

FIG. 12 is a schematic diagram showing the structure of one field of audio data in a conventional example. However, in FIG. 12, the header portion is not shown. The inner code C1 block has an 8-byte check code applied to 80-byte data, and can correct up to 3-byte errors within the block. Furthermore, the outer code C2 block has a 10-byte check code applied to each 20-byte data, and has the ability to correct up to 4 bytes per block using the erasure flag from the inner code C1 decoder.

As described above, according to the conventional example, audio sectors are provided not in all video sectors but only in certain video sectors, so that the length of the audio sector becomes longer and the error correction ability is improved. In addition, the audio sectors are distributed in the tape width direction and the digital audio signal is recorded separately into odd and even samples, reducing redundancy and preventing burst errors in the tape running direction. A recording format that exhibits high error correction capability can be obtained.

[0014]

In the conventional digital signal recording method, since the video sector and the audio sector are provided separately, there is a problem that the random error correction capabilities of the video signal and the audio signal are different.
Furthermore, there is a problem in that the error correction ability for audio signals is low for burst errors. Considering a home digital VTR, the video signal is 10 to 20M.
It is necessary to compress the audio signal to about 100 to 200 kbps per channel. The compression rate of the audio signal at this time is about 1/100 of the compression rate of the video signal, and providing separate sectors for each sector results in high redundancy and poor coding efficiency.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a digital signal recording method in which the error correction capabilities of a video signal and an audio signal are approximately equal, and the degree of redundancy is small. To provide a digital signal recording method that does not require a new increase in the number of recording bits even if the number of channels of an audio signal changes.

[0016]

[Means for Solving the Problems] The digital signal recording method of the first invention according to the present application adds an error correction code to each of a digital audio signal and a digital video signal, and provides a digital audio signal to which the error correction code is added. It is characterized in that it is recorded by superimposing it on a digital video signal to which an error correction code is added.

A digital signal recording method according to a second aspect of the present invention is the same as the first aspect, and is characterized in that the range of the superimposed recording area is made variable depending on the number of types of digital audio signals.

[0018]

[Operation] In the first invention, since the digital audio signal added with the error correction code is superimposed on the digital video signal added with the error correction code, this superposition code improves the error correction ability of the video signal and the audio signal. Make them approximately equal. Further, unlike the conventional technique, there is no need to provide an area for recording only audio signals, and the degree of redundancy is small.

In the second invention, since such a superimposition area is made variable in proportion to the number of types of audio signals, it is possible to record audio signals of any number of channels without changing the number of recording bits. It is.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to drawings showing embodiments thereof.

FIG. 1 is a schematic diagram of a recording format on a tape in the digital signal recording method of the present invention. In the figure, 1 is a video tape for a VTR, and 21 is a track on which audio signals and video signals are recorded. Here, the width of the tape 1 is 6 to 8 mm, the track pitch is 5 to 10 μm, and the linear recording density is about 60 to 100 kbpi. Considering a home digital VTR, one frame consists of about 4 tracks. .

FIG. 2 shows the recording timing and data structure on the tape 1 according to the present invention. Two tracks are formed between one field, and one track is #0 to #115.
It consists of 116 C1 blocks. One C1 block includes a 2-byte synchronization signal and an identification signal (
It consists of a total of 246 bytes: 3 bytes (hereinafter referred to as ID signal), 225 bytes of data, and 16 bytes of C1 check code. In the data portion, video data is recorded in the data portion of C1 blocks from #0 to #107, and C2 check codes are recorded in the data portion of C1 blocks from #108 to #115.

FIG. 3 shows the structure of error correction codes for video data and audio data in the present invention. The video data is composed of a product code of a (241,225,17) Reed-Solomon code (hereinafter referred to as an RS code) as a C1 code and a (116,108,9) RS code as a C2 code. Here, the (n, k, d) RS code refers to an RS code on a Galois field GF(2B) having a code length of n, an information length of k, and an inter-code distance of d. Audio data is (116,100,17)RS as C3 code
It makes up the code. The figure shows the case of 2-channel audio, with a data amount of 400 bytes per track. This C3 encoded audio sector has mod. 2 is added and superimposed.

[0024] Now, let us consider the rates of video signals and audio signals. CCIR R as video signal
ec. Assume that a (4:2:2) component signal according to the 601 standard is input. The sampling frequency of the video signal is
The Y signal is 13.5 MHz, and the RY and BY signals are each 6.75 MHz. Therefore, if each signal is quantized with 8 bits, the total data rate is 216 Mbps. On the other hand, the recording area for video signals is 225 x 108 = 24300 bytes per track, so
The data rate will be 23.328 Mbps. 21
Compression from 6 Mbps to 23.328 Mbps is performed using orthogonal transformation or the like.

[0025] The sampling frequency of the audio signal is set to 48k.
Hz and the number of quantization bits is 16 bits, the data rate of a 2-channel audio signal is 2 x 48 x 16
=1536 kbps. On the other hand, since the recording area for audio signals is 400 bytes per track, the data rate is 384 kbps. Therefore, audio data can also be converted to 1536 by orthogonal transformation.
Compress from kbps to 384 kbps.

Next, a digital VTR for realizing the digital signal recording method as described above will be explained. FIG. 4 is a block diagram showing the configuration of an example of such a digital VTR. In the figure, 8 indicates an input terminal for a video signal, and an A/D converter 9 converts the input analog video signal into a digital signal and outputs it to a high-efficiency encoder 31. The high-efficiency encoder 31 compresses the video signal at the compression rate described above (216 Mbps→23.328 Mbps). FIG. 5 is a block diagram showing the configuration of an example of the high-efficiency encoder 31. As shown in FIG. The high-efficiency encoder 31 converts the video signal into, for example, 8
Blocked into pixels x 8 pixels and subjected to discrete cosine transformation (D
An orthogonal transform circuit 61 that performs orthogonal transform such as CT) to obtain 64 transform coefficients, a delay circuit that delays the transform coefficients and transmits them to the variable length encoding circuit 64, and a standard a standard quantization circuit 63 that performs quantization; a bit number control circuit 65 that calculates the total number of bits in a predetermined block and sends a control signal to the variable length encoding circuit 64 so that the number of bits is constant; The variable length encoding circuit 64 performs encoding so that a predetermined number of bits, ie, a rate, is 23.328 Mbps or less based on a control signal. The variable-length encoded video data is output to an error correction encoder 33 and subjected to error correction encoding.

5 indicates an input terminal for audio signals;
The A/D converter 6 converts the input analog audio signal into a digital signal and outputs it to the high efficiency encoder 32. The high-efficiency encoder 32 has the same internal configuration as the high-efficiency encoder 31, and has the compression rate (1536 kbp) as described above.
s → 384 kbps). The variable-length encoded audio data is output to the error correction encoder 34 and subjected to error correction encoding. The error correction encoded video data and audio data are output to the mixing/formatting circuit 35, and the mixing/formatting circuit 35 mixes these data to create a recording format. Modulator 36 converts this recording format into a pattern for recording on tape 1. This pattern is amplified by a recording amplifier 37 and then recorded on the tape 1 by a magnetic head 40 on a rotating drum 39 when a changeover switch 38 is switched to the recording side.

Further, 41 to 51 indicate constituent members on the decoder side. When the changeover switch 38 is switched to the reproduction side, data recorded on the tape 1 is reproduced by the magnetic head 40, amplified by the reproduction amplifier 41, and output to the demodulator 42. The demodulator 42 demodulates the data pattern recorded on the tape 1 into the original recording format, and the demodulated recording format is converted into a synchronization separation/I
After being synchronously separated by the D detection circuit 43, it is output to the error correction decoder 44. The error correction decoder 44 uses the superimposed portion as an erasure and performs 4 erasure+6 error correction using the C1 code to obtain original video data. The error pattern at the erasure position obtained here is the C3 code + recording/reproduction error, and is output to the error correction decoder 45. The error correction decoder 45 performs C3 decoding on the error pattern at this erasure position to obtain the original audio data.

The high efficiency decoder 46 is an error correction decoder 44
Variable length decoding and inverse orthogonal transformation are performed on the output from the D/A converter 48 to obtain the original 8×8 pixel video data, and this data is output to the D/A converter 48. The D/A converter 48 converts it into an analog signal, and the original video signal is output from the output terminal 50. On the other hand, the high-efficiency decoder 47 performs the same processing as the high-efficiency decoder 46 on the output from the error correction decoder 45 to obtain the original audio data, and transfers this data to the D/A converter 49. Output to. The D/A converter 49 converts it into an analog signal, and the original audio signal is output from the output terminal 51.

Next, the operation will be explained. Input terminal 8
, 5, the video signal and audio signal input from
After being converted into digital signals by A/D converters 9 and 6, respectively, they are compressed to a predetermined rate as described above by high efficiency encoders 31 and 32. Thereafter, in the error correction encoder 33, the video data is first C2 encoded into a (116, 108, 9) RS code, and then (241, 225, 17) R
C1 encode to S code. On the other hand, the error correction encoder 34 converts the audio data (1
16, 100, 17) C3 encoding into RS code. The error correction encoded data is sent to the mixing/formatting circuit 3.
After being superimposed in step 5, it is formatted as shown in FIG. 2 and sent to modulator 36. Data digitally modulated by a modulator 36 is recorded onto the tape 1 from a magnetic head 40 through a recording amplifier 37 and a changeover switch 38.

During reproduction, the magnetic head 40 reproduces data from the tape, and the changeover switch 38 and reproduction amplifier 41
, the original formatted digital signal is reproduced via a demodulator 42. The original recording format is synchronously separated in a synchronous separation/ID detection circuit 43 and then input to an error correction decoder 44 . The error correction decoder 44 performs 4 erasure+6 error correction using the C1 code using the superimposed portion as an erasure. The erasure position error pattern obtained here is C3 code data + recording/reproducing error. The error pattern at this erasure position is C3 decoded by the error correction decoder 45 to obtain the original audio data. On the other hand, in the error correction decoder 44, if the code word cannot be corrected in C1 decoding, it flags the code word and
2 code is corrected in the same way as when there is no overlap. In this way, the original video data is obtained. If error correction is not possible, detect the error and send a flag along with the data. The video data output from the error correction decoder 44 is subjected to variable length decoding and inverse orthogonal transformation in the high-efficiency decoder 46 to be decoded into the original 8×8 pixel video data.
It is converted into an analog signal by the A converter 48 and sent to the output terminal 5.
The original video signal is output from 0. Here, if an error is detected, interpolation such as replacing with data one field before is performed. The audio data output from the error correction decoder 45 is also subjected to similar processing in the high-efficiency decoder 47 and D/A converter 49, and the original audio signal is output from the output terminal 51.

In the above embodiment, the case of 2-channel audio was explained, but in the case of 1-channel audio, the audio data is divided into 2×100 = 200 bytes per track, as shown in FIG. High-efficiency coding is applied to the area, and C3 error correction coding is performed. In addition, in the case of 4-channel audio, Figure 6(c)
As shown in
High-efficiency coding is performed in an area of ×100 = 800 bytes, and C3 error correction coding is performed. In this way, the superimposition area is made variable according to the number of audio signal channels. In this case, the channel number identification signal can be recorded in the ID signal recording area. That is, by detecting the number of channels in the superimposed portion from the ID signal, it is possible to know the number of channels of the audio signal and to control the error correction method.

Regarding the error correction ability of video signals and audio signals, the Institute of Electronics, Information and Communication Engineers technical report IT90-
12 Yoshida et al. “Home Digital VT Using Superposition Code”
As stated in ``Study of the code structure of R'', it is possible to make them almost the same. Furthermore, by changing the structure of the C3 code, it is also possible to control the error correction ability of the video signal and audio signal.

[0034]

[Effects of the Invention] As described above, in the first and second inventions, the digital video signal and the digital audio signal are each encoded into error correction codes, and the audio signal to which the error correction code has been added is converted into an audio signal to which the error correction code has been added. Since the signal is recorded superimposed on the video signal, the error correction capabilities of the video signal and the audio signal can be made almost equal, and a digital signal recording method with low redundancy can be achieved.

Furthermore, in the second invention, the area in which the audio signal to which the error correction code is added is superimposed and recorded on the video signal to which the error correction code is added is made variable depending on the number of types of digital audio signals. Even if the number of types of audio signals changes, there is no need to newly increase the number of recording bits.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a recording format on a tape according to the present invention.

FIG. 2 is a schematic diagram showing recording timing and data structure on a tape in the present invention.

FIG. 3 is a schematic diagram showing the structure of error correction between video data and audio data in the present invention.

FIG. 4 is a block diagram showing the configuration of a digital VTR according to the present invention.

FIG. 5 is a block diagram showing the configuration of a high-efficiency encoder according to the present invention.

FIG. 6 is a schematic diagram showing another structure for error correction of audio data according to the present invention.

FIG. 7 is a schematic diagram of a recording format on a tape in a conventional example.

FIG. 8 is a block diagram showing the configuration of a conventional digital VTR.

FIG. 9 is a schematic diagram showing recording timing on a tape in a conventional example.

FIG. 10 is a schematic diagram showing allocation of recording channels in an audio sector in a conventional example.

FIG. 11 is a schematic diagram showing a data structure within an audio sector in a conventional example.

FIG. 12 is a schematic diagram showing the structure of one field of audio data in a conventional example.

[Explanation of symbols]

1 Tape 21 Track 31 High efficiency encoder 32 High efficiency encoder 33 Error correction encoder 34 Error correction encoder 35 Mixing/format circuit

Claims (2)

[Claims] 1. An error correction code for video data for encoding a digital video signal and a digital audio signal to obtain encoded video data and encoded audio data, and for correcting errors in encoding both the signals. In the digital signal recording method of adding an error correction code for audio data to both the encoded data and recording them on a recording medium, the encoded audio data and the video data to which the error correction code for audio data is added. A digital signal recording method characterized in that the encoded video data to which an error correction code has been added is recorded in a superimposed manner. 2. A video data processing apparatus for encoding a digital video signal and some types of digital audio signals to obtain encoded video data and encoded audio data, and for correcting errors in the encoding of both the signals. In the digital signal recording method of adding an error correction code and an error correction code for audio data to both the encoded data and recording them on a recording medium, the encoded audio data to which the error correction code for audio data is added. and the encoded video data to which the error correction code for video data has been added are superimposed and recorded, and the area for this superimposition recording is variable depending on the number of types of the digital audio signals. A digital signal recording method.