JP2877338B2 - Signal recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal recording apparatus, and in particular, records a television signal obtained by time-division multiplexing a video signal for a predetermined period and an audio signal for the predetermined period. The present invention relates to an apparatus for performing the above.

[Related Art] In recent years, research on devices that handle high-definition television signals (hereinafter, simply referred to as high-definition television signals) has advanced, and various developments have been made on technologies such as imaging, transmission, recording and reproduction.

Among them, a so-called MUSE transmission system is considered to be promising as a transmission technology for broadcasting. A transmission signal by the MUSE method (hereinafter simply referred to as a MUSE signal) is a digital signal processing a Hi-Vision signal, greatly compressing the band, time-multiplexing the time-compressed digital audio signal, converting the analog signal into an analog signal, It is intended to be transmitted on a transmission line.

FIG. 8 shows a transmission signal for one frame of the MUSE signal.
As shown in the figure, the transmission signal for one frame of the MUSE signal is composed of 1125 lines, and is transmitted sequentially for each line. In FIG. 8, Y is a luminance signal obtained by converting a sample value into an analog signal, C is a color signal, A is an audio signal obtained by converting an audio signal once digitized into a ternary signal, and FP
/ VIT is a signal (VIT) and frame pulse including information such as transmission path equalization, GU is a guard space, CON is a control signal, BL is empty data, and CP is a symbol corresponding to clamp level information. I have. The numerical values shown in FIG. 8 correspond to the number of data in the digital domain before analogization of the transmission signal.

For a more detailed composition of each symbol, see 1988
Since it is disclosed in detail in Chapter 3 of "Hi-Vision Technology" edited by NHK Broadcasting Research Institute, published on March 25, the details are omitted here.

The transmission of the Hi-Vision signal by the MUSE method can be said to be an effective method in that the signal bandwidth can be sufficiently reduced and the Hi-Vision signal can be transmitted without degrading the image quality so much.

[Problems to be Solved by the Invention] However, when considering such a VTR that records and reproduces a MUSE signal on a magnetic recording medium, the following problems occur.

That is, it is necessary to consider that a dropout occurs due to the influence of dust and the like adhering to the recording medium and clogging of the magnetic head in the magnetic recording re-correction system. In other words, continuous signal periods may not be able to be reproduced,
For example, when digital recording is performed, this becomes a so-called burst error, which causes a large deterioration of the signal.

When such a dropout occurs, the dropped out signal portion is generally compensated by interpolation using the correlation of the signal. For example, in the case of a video signal, the above-described compensation is performed by inserting a signal of a portion close to the dropped-out portion on the screen.

However, for audio signals, if the period of the dropped-out portion is short, dropout compensation can be performed by holding the previous level, etc., but if a long period of dropout occurs, effective compensation is not possible. It is impossible and will be reproduced as loud noise.

On the other hand, in the above-mentioned MUSE signal, since the audio signal of one frame period is compressed on the time axis and transmitted continuously, if this MUSE signal is recorded / reproduced, it will drop out for a considerably long time. Is expected to be lost. Therefore, good reproduction of the audio signal cannot be expected.

Such a problem is not a problem peculiar to the MUSE signal, but is particularly a problem that occurs in all devices for recording a television signal in which a video signal for a predetermined period and an audio signal for the predetermined period are multiplexed on a time axis. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and in an apparatus for recording a television signal in which a video signal for a predetermined period and an audio signal for the predetermined period are time-division multiplexed, It is an object of the present invention to provide a signal recording device capable of effectively preventing deterioration of an audio signal.

[Means for Solving the Problems] For such a purpose, a signal recording apparatus according to the present invention provides an analog television signal in which a video signal for a predetermined period and an audio signal for the predetermined period are time-division multiplexed. Input means for inputting the video signal, the encoding means for digitizing the video signal and the audio signal, the separating means for separating the video signal and the audio signal multiplexed on the time axis, and separated by the separating means. A plurality of audio signal groups are formed in a period shorter than the predetermined period for the digitized audio signals for the predetermined period, and at least two of the audio signal groups for each track are digitized. Recording means for digitally recording on a recording medium by dispersing in a video signal.

[Operation] With the configuration described above, even when dropout occurs, the audio signal does not become continuously unreproducible for a long period of time, and can be compensated for by a technique such as interpolation.

[Embodiment] An embodiment of the present invention will be described below by taking a digital VTR capable of recording a baseband signal of a Hi-Vision signal and a digital MUSE signal as an example.

FIG. 1 is a block diagram showing a configuration of a recording system of a digital VTR as one embodiment of the present invention. In the figure, reference numeral 2 denotes a terminal to which a luminance signal Y of a baseband signal is inputted, 4 and 6 similarly, terminals to which a color difference signal Pb and a color difference signal Pr are inputted, and 8 an audio signal accompanying the baseband signal. The terminal 9 is a terminal to which the MUSE signal MUSE is input.

(Recording of Baseband Signal) First, recording of a baseband signal will be described.

Terminal 34 has a baseband signal recording mode or MU
Mode signal MO to specify whether to record SE signal
DE is input, and switches 10 and 36 are connected to the B terminal by this signal MODE for recording a baseband signal and the like. At this time, the luminance signal Y is supplied to the A / D converter 12 via the switch 10, and is converted into an 8-bit digital signal by the A / D converter 12.

The sampling frequency fs of the A / D converter 12 is set to 4
At 4.55 MHz, the effective number of pixels per line is 1152
And the bit rate becomes 356.4 Mbps. At such a high bit rate, when recording on a VTR, recording for a long time is impossible, and the data processing speed becomes too fast, so that the digital luminance signal from the A / D converter 12 The band is supplied to the compressor 14, and the band is compressed. As the band compressor 14, a sub-sampling circuit, a well-known high-efficiency coding circuit, or the like can be applied. In this embodiment, the number of pixels is reduced to 1/2 by sub-sampling,
It is assumed that the information amount is reduced to ビ ッ ト by converting the bit signal into 4 bits by predictive difference coding (DPCM).

The luminance signal data band-compressed by the compressor 14 is supplied to a memory circuit 16 functioning as a bit converter and a buffer, and a process of converting two 4-bit data into one 8-bit data, a color signal and an audio signal described later. Is performed to adjust the timing of the operation. As a result, the luminance signal output from the circuit 16 is 288 symbols per line.

On the other hand, the color difference signals Pb and Pr input from the terminals 4 and 6 are respectively
Sampling frequency 22.275MHz by A / D converters 20 and 26
, And is supplied to the band compressors 22 and 28 in the same manner as the luminance signal. Assuming that these band compressors 22 and 28 also reduce the number of pixels by subsampling to 1/2 and further convert the 8-bit signal to 4 bits by DPCM, these two 4-bit color difference signals Pb and Pr are combined. The bit data has 288 symbols per line, which is equal to that of the luminance signal.

Further, the audio signal input from the terminal 8 is sampled at 51.84 MHz by the A / D converter 30 to be 16-bit data, and is converted to 8-bit data by the buffer 32. As a result, audio data of 3456 symbols is obtained per frame.

Here, the sampling clock supplied to the A / D converters 12, 20, 26, and 30 is obtained from a clock generator 42 constituted by a PLL to which a synchronization signal SYNC separated from an analog HDTV signal is input. Figure clock a clock of 22.275MHz, clock b are clock 44.55MHz, the clock e is a clock of 51.84KH _z.

Here, the format in which the digital data including the above-described luminance signal, color signal, and audio signal are recorded in a subsequent circuit will be described with reference to FIGS. 3 and 4. FIG.

FIG. 3 is a diagram showing the data structure of one track in the digital VTR of the present embodiment. In FIG. 3, Y201 is a symbol of a luminance signal, Pb and Pr203 are symbols of a color difference signal, and A is a symbol of an audio signal. As shown, three C1 parities are added to each of the 144 luminance signal symbols after compression for 1/2 line and the 144 color difference signal symbols after compression. Further, there are three ID data symbols 205 indicating the positions of these data on the screen,
One sync block with two YNC symbols 206 added
207 are configured.

By the way, in the VTR of the present embodiment, it is assumed that information of one frame obtained by the above-described processing is divided into 12 tracks and recorded. This means that, assuming a VTR in which a tape is wound around a rotating head cylinder in an angular range of 180 degrees or more and the signals of each channel are recorded alternately by two heads, the rotating speed of the rotating head cylinder is 3600 rpm. This can be realized by setting the number of recording channels to three.

According to the BTA studio standard, the number of effective lines
However, considering that one frame of information obtained by the above-described processing is recorded on 12 tracks, the effective lines are set to 1044 (87 × 12) lines, and audio signals and sub-signals are set. 84 more for code signals etc.
Prepare a line. Thereby, the number of lines of the information signal per frame, that is, the number of synchronization blocks is 1128 (87 × 12).
Thus, the number of synchronous blocks per track is 188, which is the synchronous blocks (1) to (188) in FIG. Since the audio signal has 288 symbols per track, an audio signal of up to seven channels can be recorded according to the data format described above.

Further, in the data matrix of each track shown in FIG. 3, four C2 parities are added in the vertical direction. That is, the data at the same position in the odd-numbered synchronous block and the data at the same position in the even-numbered synchronous block in FIG. As a result, a synchronous block consisting of only a total of eight error correction codes is added to the data of each track.

FIG. 4 is a diagram showing a recording format of a track actually recorded on a tape in the VTR of the present embodiment. The tracking control pilot signal of the data recording area 214 according to the data matrix shown in FIG. A recording area (ATF) 211, a clock area (CRI) 213, and a gap space (IBG) 212 are provided. The size of each of these areas corresponds to a recording area for one synchronous block of data, and corresponds to an area for a total of four synchronous blocks.

The shortest recording wavelength of the VTR according to the present embodiment, which performs recording according to the above-described format, is about 0.53 μm when recording on a 1 / 2-inch tape, which is a value that can be easily realized at present.

Here, returning to FIG. 1, the description will be continued. The switch 18 is a data selector for selectively outputting the above-mentioned luminance signal, color difference signal, and audio signal.
It is output from 6, 24, 32 at a predetermined timing that does not overlap. The data selector 36 outputs the output of the selector 18 and writes it to a RAM (random access memory) 38 via the selector 60. At this time, the write address of the RAM 38 is, via the switch 44, a write address generator supplied with a clock d having a frequency that is an integral multiple of 44.55 MHz.
Determined by 46.

FIG. 6 is a diagram showing an arrangement of baseband signals in the RAM 38, where 1, 2,... 576 are horizontal addresses corresponding to horizontal symbol numbers, 1, 2,. 1128 is a vertical address corresponding to the line number, and has a capacity of 8 bits per address. That is, for two pixels of the luminance signal, two pixels for one of the two types of color difference signals are combined.
Corresponds to the address. A video signal is stored in a portion of the vertical address 1 to 1044, and an audio signal and a subcode are stored in a portion of 1045 to 1128.

Next, reading from the RAM 38 will be described. At the timing of reading, the data selector 48 selects the output of the read address generator 50. The read address generator 50 operates according to a clock of a predetermined frequency corresponding to the recording bit rate from the oscillator 52.

In accordance with this, data for three tracks is read from the RAM 38 every time the rotary cylinder makes a half turn, and the read data is a three-channel ECC (error correction signal).
It is distributed to the encoders 54-1, 54-2, 54-3. The outputs of the ECC encoders 54-1, 54-2, 54-3 are supplied to synchronization and ID data addition circuits 56-1, 56-2, 56-3, and after the above-described synchronization data and ID data are added, Modulators 54-1,54-2,54
-3 is digitally modulated. The modulated three-channel signals are further amplified to predetermined levels by recording amplifiers 60-1, 60-2, and 60-3, and output via terminals 62-1, 62-2, and 62-3 (not shown). The data is supplied to the recording system of the channel and is recorded on the magnetic tape.

(Recording of MUSE Signal) Next, recording of the MUSE signal according to the present invention will be described.

In the recording mode of the MUSE signal, the switches 10, 44 and the data selector 36 all output M-side signals according to the mode signal MODE, and the MUSE signal input to the terminal 9 is supplied to the A / D converter 12. The MUSE signal is an 8-bit signal sampled at 16.2 MHz as a digital signal before transmission. In the VTR of the present embodiment, the input MUSE signal is also converted into a digital signal by a clock c of 16.2 MHz from the clock generator 42.
Convert to bits. As a result, a digital MUSE signal of 480 symbols per line is obtained.

On the other hand, this digital MUSE signal is supplied to the audio separation circuit 65, where only the audio signal is separated and demodulated. The separation and demodulation of the audio signal from the MUSE signal is also disclosed in detail in Chapter 3 of "Hi-Vision Technology" edited by NHK Broadcasting Research Institute, published on November 25, 1988. Omitted.

The above digital MUSE signal is used as is with data selector 3.
It is supplied to RAM 38 via 6,66. The audio signal separated from the MUSE signal (hereinafter simply referred to as a separated audio signal) is also supplied to the RAM 38 via the buffer 63 and the selector 66. At this time, the sampling clock c of the MUSE signal is supplied to the write address generator 46.

FIG. 7 is a diagram showing the arrangement of the MUSE signal in the RAM 38. As shown, the vertical address is 1-1125 and the horizontal address is 1-4.
The data is stored in the area of 80 in accordance with the clock c. In the remaining address 152 indicated by the hatched portion in the figure, the above-described separated audio signal is stored via the data selector 66. The reading of the data from the RAM 38 and the subsequent processing are exactly the same as the operation at the time of recording the baseband signal, and therefore the description is omitted.

FIG. 5 shows the data structure of one track of the digital MUSE signal and the separated audio signal thus recorded.
In FIG. 5, MD indicates a symbol of the digital MUSE signal,
A indicates the separated audio signal data described above. As shown in the figure, two sets of 144 symbols are prepared by adding 24 symbols of the separated audio signal data to 120 symbols of the digital MUSE signal, and a c1 parity of 3 symbols is added to each of them. Furthermore, a synchronous block is obtained by adding ID data of three symbols and synchronous data of two symbols.

As a result, up to the first 144 symbols of the synchronous block (188) become symbols of the digital MUSE signal and the separated audio signal, and the remaining data of the synchronous block (188) is dummy data. This is because the digital MUSE signal consists of 1125 lines per frame, and one line is associated with one synchronization block.
This is because the number of synchronous blocks of the MUSE signal is (1125/8 =) 187.5. For the synchronous blocks (189) to (196), c2 parity is allocated in the same manner as when recording the baseband signal. The actual recording pattern on the tape is the same as that at the time of recording the baseband signal shown in FIG.

(Reproduction) Next, the operation at the time of reproduction of the present embodiment will be described.

FIG. 2 is a diagram showing a configuration of a reproduction system of the VTR according to the present embodiment. 3 played by the club
A channel reproduction signal is input. The reproduced signals of the three channels are amplified to predetermined levels by the reproducing amplifiers 70-1, 70-2, and 70-3, and digitally demodulated by the demodulators 72-1, 72-2, and 72-3. The processing at this time is performed by a clock formed by a PLL (not shown) in synchronization with a clock component including jitter included in the reproduced signal.

The three-channel signals written to the first-in first-out memory (FIFO) 74-1, 74-2, 74-3 in synchronization with the clock including the jitter are read out by the clock of a stable constant frequency from the oscillator 80. This is a digital signal from which jitter has been removed. And FIFO74-1,74-
The digital signal read from 2,74-3 is an ECC decoder 86
After correcting a code error generated in the magnetic recording / reproducing system by -1,76-2,76-3, it is written into the RAM 78.

The write address to the RAM 78 is determined by the write address generator 84 while referring to the ID data in the reproduction signal in synchronization with the clock output from the oscillator 80. The data selector 90 naturally outputs the address data output from the write address generator 84 to the RAM 78 at the data write timing.
To supply. The processing up to this point is exactly the same whether the recorded signal is a baseband signal or a digital MUSE signal. As a result, if the recorded signal is a baseband signal, data is written into the storage area of the RAM 78 as shown in FIG. 6, and if the recorded signal is a MUSE signal, the data is written. Data writing is performed as shown in FIG.

The read address generator 86 has the same frequency as the recording system clock d, and generates a read address according to the clock d 'obtained from the clock generator 82. If the recorded signal is a baseband signal, the mode signal MODE input from the terminal 95 causes the address generator
The address data from 86 is supplied from selector 90 to RAM 78. As a result, the above-described luminance signal, color difference signal, and audio signal of the baseband signal are output in a time-division manner.

81 is a 4-bit luminance signal composed of two DPCM codes.
A buffer having a bit conversion function to output at a constant rate as the DPCM code, digital signals from the buffer 81 is processed, such as DPCM decoding and interpolation is performed by the band expander 83, the digital luminance of the original 44.55MH _z Returned to a signal.
At this time, the D / A converter 87 outputs 44.55 MHz from the clock generator 82.
_The analog luminance signal obtained by the operation of the clock b 'of _z is output from the output terminal 91 via the B-side terminal of the switch 89.

A conversion function 98 receives the two types of color difference signals described above and divides them into a DPCM code of a 4-bit color difference signal Pr and a DPCM code of a 4-bit color difference signal Pb and supplies them to the band extenders 99 and 100 at a constant rate. Is a buffer having Band extender
In 99,100, the original 8-bit color difference signals Pr, Pb are restored,
Further subjected to interpolation to respectively the digital signal 22.275MH _z, supplied to the D / A converter 101 D / A converter 101 and 102
Operates by a clock a 'of 22,275MH _z from the clock generator 82, thereby resulting analog color difference signals
Pr and Pb are output from output terminals 103 and 104.

Further, the buffer 92 receives the above-mentioned audio signal and outputs it at a constant data rate.
After returning to the original analog audio signal by the D / A converter 94 which operates at a clock e 'of H _z, output from the output terminal 96.

On the other hand, the read address generator 88 generates a read address according to the clock c 'obtained from the clock generator 82 and having the same frequency as the clock c of the recording system. If the recorded signal is a digital MUSE signal, the address data from the address generator 88 is transferred from the selector 90 to the RAM 7
Supply 8 As a result, the digital MUSE signal and the separated audio signal described above are output from the RAM 78.

At this time, the data selector 85 outputs the data on the M side according to the mode signal MODE.
It is input to the D / A converter 87. At this time, the D / A converter 87 operates by the clock c ', and the original analog MUSE signal is output from the output terminal 93 via the M-side terminal of the switch 89.

Further, the buffer 108 receives the separated audio signal and outputs it at a constant data rate, and the D / A converter 106
After that, an analog audio signal is output from the output terminal 107.

In the digital VTR having the above-described configuration, recording and reproduction are performed without changing the data format of the MUSE signal at all, so that it is extremely easy to reconstruct the MUSE signal during reproduction, and that the audio signal can be reproduced. Is
Since the audio signal separated from the MUSE signal is dispersedly recorded in each synchronization block, even if a dropout or the like occurs at the reproduction location, the audio signal does not significantly deteriorate.

In the above-described embodiment, all the data of the digital MUSE signal are recorded on the same data matrix as the baseband signal and recorded.However, for example, only the line containing the video information in the MUSE signal is regarded as the baseband signal. It is also possible to perform recording by arranging them on the same data matrix.

In the above-described embodiment, the MUSE signal has been described as an example.However, the scope of the present invention is not limited to this, and a video signal for a predetermined period and an audio signal for the predetermined period are time-division multiplexed. The present invention can be applied to a case where a television signal is recorded.

[Effects of the Invention] As described above, according to the present invention, when recording a television signal in which a video signal for a predetermined period and an audio signal for the predetermined period are multiplexed on a time axis, dropout or the like may occur. A signal recording device capable of effectively preventing the deterioration of the audio signal due to the influence was obtained.

[Brief description of the drawings]

1 is a diagram showing a configuration of a recording system of a digital VTR as one embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a reproduction system of the digital VTR of FIG. 1, and FIG. 3 is a diagram of FIG. FIG. 4 shows a data format when a baseband signal is recorded in a recording system, FIG. 4 shows a recording format on a tape in the recording system of FIG. 1, and FIG. 5 shows a digital MUSE in the recording system of FIG. FIG. 6 is a diagram showing a data format when a signal is recorded, FIG. 6 is a diagram showing a data arrangement of baseband signals on a RAM in the recording system of FIG. 1, and FIG. 7 is a diagram on a RAM in the recording system of FIG. Digital MUSE
FIG. 8 is a diagram showing a data arrangement of signals, and FIG. 8 is a diagram showing a transmission signal for one frame of a digital MUSE signal. In the figure, 9 is a terminal to which a MUSE signal MUSE is input, and 56-1, 56-
2, 56-3 are synchronization / ID addition circuits, 65 is a voice separation circuit,
66 is a selector.

Continuing from the front page (72) Inventor Shinshu Yamashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shin Shimokoriyama 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon stock In-company (56) References JP-A-63-44369 (JP, A) JP-A-63-244370 (JP, A) JP-A-62-80872 (JP, A) JP-A-63-83970 (JP, A) JP-A-63-175266 (JP, A) JP-A-62-73461 (JP, A) JP-A-63-29377 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 20 / 00,20 / 12,20 / 10 H04N 5/92

Claims (1)

(57) [Claims] 1. An input means for inputting an analog television signal obtained by time-divisionally multiplexing a video signal for a predetermined period and an audio signal for the predetermined period, and digitizing the video signal and the audio signal Encoding means; separating means for separating the video signal and the audio signal multiplexed on the time axis; and the digital signal for the predetermined time period separated by the separating means from the predetermined time period. Also form a plurality of audio signal groups in a short period of time, at least two said audio signal groups for each track,
Recording means for digitally recording the digitalized video signal on a recording medium in a dispersed manner.