JP2815882B2 - Digital recording / playback device for video signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial application field The present invention is a band compression transmission system of a Hi-Vision signal.
The present invention relates to a video recording / reproducing apparatus for digitally recording a MUSE signal on a recording medium such as a magnetic tape or an optical disk.

(B) Conventional technology Recently, high-definition television has been developed for practical use as a near-generation television. The output signal of the HDTV camera has a bandwidth of 30MHz for both RGB signals. In order to broadcast this Hi-Vision signal on one channel of satellite broadcasting, it is necessary to perform band compression to a baseband signal bandwidth of about 8 MHz. To achieve this, MUSE
A band compression method called (Multiple Sub-Nyquist Sampling Encoding) method was developed by NHK. For details of this MUSE method, see NHK Technical Research (Vol. 39, No. 2, P.1
8-P.53, published in September 1987), Journal of the Institute of Television Engineers of Japan (V
ol.42, No.8.P51-P.58, issued in August 1988).

Hereinafter, the MUSE method will be briefly described. FIG. 5 is a diagram showing a configuration example of a MUSE encoder. After limiting the HDTV video signal with a low-pass filter (501) with a cutoff frequency of 21 to 22 MHz, the sampling frequency is 48.6 MHz.
A / D conversion is performed (502). Next, reverse processing (503) of the camera gamma characteristic is performed, and the matrix (504) converts the luminance (Y) signal and two color (C) signals. The C signal is further band-limited by a low-pass filter (505), time-division multiplexed with the Y signal, and TCI (Time Compressed Integration).
It is signalized (506).

Filter processing and sub-sampling processing (507 and 508) are performed on this signal in parallel for still images and for moving images, respectively. Further, the degree of motion of the image is detected by the motion detection circuit (509), and the still image processing (50
7) and the output of the moving image processing (508) is proportionally mixed (510). Thereafter, the transmission path gamma processing (511) and the emphasis processing (512) are performed. The video signal, the control signal, the synchronization signal, and the audio signal from the audio encoder (514) are multiplexed and configured as shown in the signal format of FIG. This is subjected to D / A conversion (515), band-limited by a low-pass filter (516), and output as a MUSE signal. The transmission format of the MUSE signal will be briefly described. The sampling frequency of the MUSE signal is 16.2
MHz, and there are 480 sample points in the 1H period. Among them, HD
(Horizontal synchronization signal) is 11 sample points, C is 94 sample points, Y is
One guard point is assigned between 374 sample points and Y and C to prevent signal interference. The two C signals are line-sequentially multiplexed with RY on odd lines and BY signals on even lines. Further, as shown in Table 1, a sub-sample phase, a motion vector amount, a code for identifying FM modulation or AM modulation at the time of transmitting a MUSE signal, and the like are transmitted as a control signal for each field. In addition, during the vertical blanking period, voice / additional information at a rate of 1.35 Mbit / sec, a VIT signal used for transmission path equalization, and a clamp level signal used to define the neutral level of the C signal or to use it for AFC or the like are multiplexed. .

FIG. 6 is a diagram showing an example of the configuration of a MUSE decoder, which basically performs a process reverse to that of an encoder to obtain a Hi-Vision RGB signal.

Note that when transmitting MUSE signals by FM using satellite broadcasting, etc.
9 (a) and 9 (b) with the emphasis circuit of FIG.
The emphasis and the non-linear processing shown in FIG. In the de-emphasis circuit of FIG. 6 (604), FIG.
The processing of the characteristic shown in (d), that is, the characteristic opposite to that of (a) and (b) is performed.

For example, in the MUSE encoder, a video signal that changes from white to black to white as shown in FIG. 9E is emphasized by the emphasis processing of FIG. The signal waveform of (g) is obtained by the nonlinear processing of (b). This is FM-transmitted, and the signal waveform (h) after reception becomes the signal waveforms (i) and (j) by the de-emphasis processing (C) and the inverse nonlinear processing (d) in the MUSE decoder.

However, in the case of AM transmission, these emphasis and de-emphasis processes are not performed.

The above is the outline of the MUSE method. Next, an apparatus for recording and reproducing the MUSE signal will be described.

An analog recording system and a digital recording system can be considered as a recording / reproducing device of the MUSE signal, and a magnetic tape, an optical disk, and the like can be considered as a recording medium. this house,
A so-called digital VTR for digital recording on a magnetic tape will be described. An example of this is disclosed in JP-A-62-238.
Publication No. 184 (H04N 5/92) "MUSE video recording / reproducing device"
There is. This will be described with reference to FIG.

MUSE signal input to input terminal (901) is band-limited by low-pass filter (902) and A / D converter (903)
To convert to a digital signal. The MUSE signal is transmitted as a sample value, and this sample value must be generated accurately. Therefore, the MU is controlled by the PLL circuit (904).
Generates a 16.2MHz resampling clock synchronized with the SE signal, and performs A / D conversion with this clock. The MUSE digital signal thus obtained is compressed on the time axis (905), and an error correction code is added to the vacant time axis (906). After that, the modulator (907), the recording amplifier (908), and the switch (90
9) After passing through the rotating transformer (910), the rotating magnetic head (91
Record on magnetic tape (912) according to 1).

At the time of reproduction, the signal reproduced by the rotating magnetic head (911) is amplified by the reproducing amplifier (913) through the rotating transformer (910) and the switch (909). This is demodulated (914), and the time axis correction circuit (915) corrects the fluctuation of the time axis of the rotating magnetic head. Next, code error correction and correction (916) are performed,
The time axis is returned to the state before recording by the time axis expansion circuit (917). After that, D / A conversion (918) is performed, the band is limited by a low-pass filter (919), and output from an output terminal (920).

(C) Problems to be Solved by the Invention As described above, when FM transmission is performed, the video portion of the MUSE signal is subjected to emphasis processing. So this MUSE
When a signal is recorded by a conventional digital signal recording / reproducing apparatus, as shown in FIG. 9 (j), in order to obtain a video signal from a black level to a white level with 8-bit precision (-128 to 127), it is necessary to use (h) The signal must be quantized with 10-bit precision (−512 to 511), and a digital signal having 10-bit quantized bits must be recorded. That is, in general, to obtain a video signal with N-bit precision (N: integer), N + 2 bits of quantization bits are required. This increases the recording bit rate in a digital signal recording / reproducing apparatus, which is problematic.

(D) Means for Solving the Problems In the present invention, the emulated MUSE signal is recorded after the de-emphasis processing. Specifically, the MUSE signal is quantized with M bits, and then converted into N (M> N) bits by de-emphasis and bit conversion processing, and recorded. In another configuration of the present invention, the MUSE signal in the AM mode is forcibly output during reproduction.

(E) Operation By recording and reproducing the MUSE digital signal after the de-emphasis processing, the operation is performed to reduce the number of quantization bits required for a predetermined S / N of the video signal. That is, the recording bit rate in the MUSE digital signal recording / reproducing device is reduced. At the time of reproduction, since the AM mode is forcibly set and output, the VTR does not require an emphasis circuit.

(F) Embodiment As an embodiment of the present invention, a digital VT for recording / reproducing a digital signal on / from a magnetic tape by using a rotating magnetic head.
R will be described with reference to the block diagram of FIG.

The MUSE signal input to the input terminal (101) is band-limited to 8.15 MHz by a low-pass filter (102), and the A / D converter (10
Convert to digital signal in 3). At this time, the PLL circuit (10
According to 4), a resampling clock of 16.2 MHz synchronized with the MUSE signal is generated, and sampling is performed using this clock. Further, it is assumed that A / D conversion is performed to a 10-bit 2'S complement (2's complement) code based on the clamp level of the MUSE signal. Thereafter, the separation circuit (105) separates the video signal, the audio signal, and the control signal. And
The de-emphasis circuit (106) performs a de-emphasis process on the video signal, further performs an inverse gamma correction process for the transmission path (140), and then performs a first bit number conversion circuit (107)
Performs 10-bit to 8-bit conversion.

As shown in FIG. 9 (j), since the video signal after the de-emphasis processing falls within the level of -128 to 127, the conversion from 10 bits to 8 bits is performed simply by converting the most significant code bit and the lower 7 bits. I just need to take it out.

The audio signal processing circuit (108) performs ternary identification of the audio signal and conversion from the ternary signal to a binary signal. The control signal processing circuit (109) performs binary identification of the control signal. The video, audio, and control signals that have undergone these processes are written to the memory (110).

The parity generation circuit (111) generates a vertical parity and a horizontal parity for the audio and video data stored in the memory (110) so as to form the correction block shown in FIG. ). As shown in Figure 2, correction block is n ₁ word speech horizontally, n ₂ words of video, constituted by a horizontal parity n ₃ words, in the vertical direction m ₁ word audio or video, m ₂ Consists of word parity. The correction block constitutes one track with K blocks, and further, one track of video, audio, and control data is recorded with L tracks.

After the parity is generated, audio data, video data, control data, and parity are sequentially read from the memory (110) and input to the frame synthesis circuit (112) while distributing to each channel. Here, a frame as shown in FIG. 3A is configured. l ₁ word sync signal,
l One frame is composed of a _2- word address signal, (n ₁ + n ₂ + n ₃ ) -word video data, audio data, and parity. That is, a synchronization signal and an address signal are added to one horizontal line of the correction block in FIG. 2 and are sequentially transmitted. At this time, a synchronization signal is output by the synchronization signal generation circuit (113), and an address signal is output by the address signal generation circuit (114).

On the other hand, as for the control signal, as shown in FIG. 3B, a frame is formed by adding a synchronization signal ₁₁ word and an address signal ₁₂ word to the head. If necessary, correction parity is added or multiplex writing is performed.

Also, in a digital VTR for recording with a rotary head, a preamble portion and a postamble portion are provided at a switching portion of the head, that is, at both edges of a recording track. This is due to a margin at the time of head switching, a pull-in time of clock reproduction, absorption of cylinder rotational jitter, and the like. The preamble and postamble signals are usually signals having a fixed frequency which is the highest recording frequency of a digitally recorded signal or a fraction of the highest recording frequency. These signals are generated by a preamble and postamble signal generation circuit (115),
This signal and the output signal of the frame synthesizing circuit (112) are synthesized by the synthesizing circuit (116). After that, the digital modulation circuit (1
Modulate by 17) and amplify by recording amplifier (118). The switching circuit (119) performs switching between recording and reproduction, and at the time of recording, switches two-channel signals from the recording amplifier (118) to two systems according to the rotation phase of the rotary head, respectively, via the rotary transformer (120). Rotating magnetic head (12
1) Record on the magnetic tape (122).

At this time, the signal format of the track recorded on the magnetic tape is as shown in FIG. Recording a preamble signal S ₁ frame on the magnetic tape inlet side, then S ₂
Control signal of the frame, voice, video and parity signals S ₄ frames, recording a control signal S ₂ frame further subsequently record a postamble signal S ₃ frames.

At the time of reproduction, a signal recorded on a magnetic tape (122) is read out by a rotary magnetic head (121), and is reproduced via a rotary transformer (120) and a switching circuit (119).
And amplify. Then, the characteristic lost in the magnetic recording system is compensated for by the waveform equalizing circuit (124), and the clock generation (125) is performed based on the reproduced signal. Using this clock, the signal after waveform equalization is demodulated by the demodulation circuit (126) into the original digital signal. And synchronization detection (127)
And the sync separation / S /
The data is separated by the P conversion circuit (128) and S / P (serial to parallel) conversion is performed. This data is written to the memory (129) in word units. The error correction / correction circuit (130) performs error correction or correction processing on the video, audio, and control signals written in the memory (129).

These corrected and corrected video, audio, and control signals are read from the memory (129). The video signal is converted from 8 bits to 10 bits by the second bit number conversion circuit (131), and then gamma correction for the transmission path is performed (139). Further, FIG. The emphasis processing shown in b) is performed. The audio signal is converted from a binary signal to a ternary signal by an audio signal processing circuit (133), and a ternary level represented by 10 bits is assigned to the ternary signal. A binary level represented by 10 bits is assigned to the control signal by the control signal processing circuit (134). After performing these processes,
The signal is synthesized by the synthesizing circuit (135), is configured in the signal format shown in FIG. 7, is subjected to D / A conversion (136), and is subjected to a low-pass filter (137).
, And output from the output terminal (138).

As described above, the digital VT according to the embodiment of the present invention
R can solve the problem that recording and reproduction of a MUSE signal requires recording and reproduction of a signal having 10-bit quantization bits in order to obtain a video signal with 8-bit precision.

In this embodiment, the MUSE signal is recorded, and the reproduced signal is also recorded.
It is an example of a digital VTR that outputs with a MUSE signal. Therefore, in order to display a reproduced signal on a monitor, a Hi-Vision signal is obtained via a MUSE decoder, and this is connected to a Hi-Vision monitor. Separately, digital VTR
A device that combines a USE decoder and directly obtains a Hi-Vision signal from a reproduced signal is also conceivable. In this case, in the digital VTR of FIG. 1 and the MUSE decoder of FIG. 6, the output of the separation circuit (603) and the de-emphasis circuit (6
The output of 04) may be replaced with the output of the memory (129) in FIG. At this time, the circuits (131) to (137) in FIG. 1 and the circuits (601) to (604) in FIG. 6 become unnecessary.

In the above configuration, the MUSE signal is output as the output of the VTR. Therefore, the same emphasis circuit (132) as that provided in the encoder (see FIG. 5) is required in the VTR reproduction circuit. Therefore, the circuit scale becomes large. FIG. 10 takes this point into account. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

Although omitted in the configuration of FIG. 1, according to the state of the 20th bit (“1” or “0”) in the control signal (see FIG. 11 for the control signal) included in the MUSE signal, And a signal selection circuit (141) for selecting a video signal processed by the de-emphasis circuit (108) or a video signal (143) not processed by the de-emphasis circuit (108). That is,
In the case of FM modulation with emphasis, the 20th bit of the control signal is "0", and the output of the de-emphasis circuit (106) is selected. 2 for AM modulation
The 0th bit becomes “1”, and selects a video signal that is not subjected to de-emphasis processing. Note that this signal selection circuit (14
1) includes an inverse gamma correction circuit (140 in FIG. 1) and a bit conversion circuit (107 in FIG. 1). Output to (110). And the subsequent recording and playback
It is almost the same as the case of FIG. However, in order to omit the emphasis circuit when outputting, the 20th bit of the output control signal is forcibly set to “1” indicating AM modulation.
(Performed in the control signal processing circuit (134)). This allows the monitor to be supplied with the playback output
The TV decoder processes the video signal without de-emphasis.

In the above description, the control signal is set to a state without emphasis at the time of reproduction. However, the same setting can be performed before recording on the recording medium (performed by the control signal processing circuit (109)).

Although the de-emphasis process is performed after the A / D conversion in the configurations of FIGS. 1 and 10, a configuration in which the de-emphasis is performed in the state of the analog signal and the A / D conversion is performed is also conceivable. By doing so, the amplitude of the signal to be A / D converted becomes small, and the required number of bits can be reduced.

(G) Effect of the Invention As described above, according to the present invention, the number of quantization bits required for recording a video signal can be reduced, and the recording bit rate can be reduced.

In addition, since the AM mode without emphasis is forcibly set for the output signal at the time of reproduction, the emphasis circuit can be omitted.

[Brief description of the drawings]

FIGS. 1 and 10 are block diagrams showing an embodiment of the present invention, FIGS. 2, 3 and 4 are explanatory diagrams for explaining the format of a signal to be recorded, and FIG. 5 is a MUSE encoder. FIG. 6 is a block diagram showing a MUSE decoder, FIG. 7 is an explanatory diagram showing a transmission format of a MUSE signal, FIG. 8 is an explanatory diagram of emphasis and de-emphasis operations, and FIG.
FIG. 11 is a block diagram showing a conventional MUSEVTR, and FIG. 11 is an explanatory diagram of control signals. (103) A / D converter, (106) De-emphasis circuit, (107) Bit conversion circuit, (134) Control signal processing circuit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tateo Toyama 2--18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-2-116281 (JP, A) (58) Surveyed fields (Int.Cl. ⁶ , DB name) H04N 5/91-5/956

Claims (3)

(57) [Claims] An image signal transmitted by emphasis processing is subjected to de-emphasis processing, the number of bits required by a first bit number conversion circuit is reduced and recorded, and the recorded video signal is converted to a second bit number. A digital recording / reproducing apparatus for video signals, characterized in that the number of bits is increased to the original number of bits by a number conversion circuit, and emphasis processing is performed for reproduction. 2. A MUSE signal generated by band-compressing a Hi-Vision signal and subjected to emphasis processing for FM transmission is quantized by M bits (M is a natural number). De-emphasis processing is performed on the digital signal, and converted to N (M> N) bits for recording. In addition, the recorded N-bit MUSE digital signal is converted to the original M bits, and emphasis processing is performed for reproduction. Digital recording / reproducing apparatus for video signals. 3. A digital recording / reproducing apparatus for recording / reproducing a MUSE signal generated by band-compressing a Hi-Vision signal, wherein the emulated MUSE signal is recorded with a reduced number of bits after de-emphasis processing and recorded. A digital signal recording / reproducing apparatus for reproducing a video signal without performing emphasis processing by increasing a recorded video signal to an original number of bits at the time of reproduction.