JPH02183681A - Digital recording and reproducing device for video signal - Google Patents

Abstract

PURPOSE:To reduce a recording bit rate by deemphasizing an emphasized video signal and recording the result. CONSTITUTION:An emphasized MUSE signal or the like is subject to de- emphasis processing and the resulting signal is recorded. That is, the MUSE signal is quantized in M-bit and converted into N (M>N) bits by de-emphasis bit conversion processing and the MUSE digital signal after processing is recorded and reproduced. As a result, it is possible to reduce the quantized bit number required for a prescribed S/N of the video signal. Then the recording bit rate is reduced.

Description

[Detailed description of the invention] (a) Industrial application field The present invention is a band compression transmission system for high-definition signals.
The present invention relates to a video recording/reproducing device that digitally records a USE signal on a recording medium such as a magnetic tape or an optical disk.

(b) Conventional technology Recently, high-definition television is being developed for practical use as the next generation of television. The output signals of the high-definition camera have a bandwidth of 30 MHz for both RlG and B signals. In order to broadcast this high-definition signal on one satellite broadcasting channel, the baseband signal bandwidth is approximately 8M.
It is necessary to perform band compression down to Hz. In order to achieve this, MUSE (Multiple 5ub-
Nyquist Sampling Enc.

A band compression method called the ding) method was developed by NHK. For details of this MUSE method, see NHK Technical Research (Vol. 39, No. 2, P, 18-P.).

53, published September 1986), Journal of the Television Society (V
ol, 42, Na3. P 51-P, 58, published in August 1986), etc.

This MUSE method will be briefly explained below. Fifth
The figure is a diagram showing an example of the configuration of a MUSE encoder. After band-limiting the high-definition video signal using a low-pass filter (501) with a cutoff frequency of 21 to 22 MHz, A/D conversion is performed at a sampling frequency of 48.6 MHz (502).

Next, inverse processing (503) of the camera gamma characteristics is performed, and a matrix (504) is used to calculate the luminance (Y) signal and the two colors (C).
Convert to signal. The C signal is further band-limited by a low-pass filter (505), and is time-division multiplexed together with the Y signal to generate T CI (Time Compressed In).
(tegration) signal (506').

Filter processing and subsampling processing (507° and 508) are performed on this signal in parallel for still images and moving images, respectively. Further, a motion detection circuit (509) detects the degree of motion of the image, and proportionally mixes (510) the outputs of the still image processing (507) and the moving image processing (508). After that, gamma processing for transmission line (511)
, performs emphasis processing (512). This video signal, control signal, synchronization signal and audio encoder (5
The audio signals from 14) are multiplexed and configured as in the signal format shown in FIG. This is band-limited by a D/A converter (515) L and a low-pass filter (516), and becomes the MUSE signal output. The transmission format of this MUSE signal will be briefly explained. The sampling frequency of the MUSE signal is 16.2
MHz, and there are 480 sample points during the initial IH period. Of these, HD (horizontal synchronization signal) has 11 sample points, C has 94 sample points, Y has 374 sample points, and a guard area between Y and C to prevent signal interference has 1 sample point. It is being The two C signals are line-sequentially multiplexed, with the R-Y signal on the odd-numbered lines and the B-Y signal on the even-numbered lines. Further, as shown in Table 1, the subsample phase, motion vector amount, code for identifying FM modulation or AM modulation during MUSE signal transmission, etc. are transmitted for each field as a control signal. In addition, during the vertical blanking period, audio/additional information at rates of 1 and 35 Mbit/sec, a VIT signal used for transmission path equalization, and a clamp level signal used for specifying the neutral level of the C signal and for AFC, etc. are multiplexed. ing.

FIG. 6 is a diagram showing an example of the configuration of a MUSE decoder, which basically performs the opposite process to that of an encoder to obtain high-definition R, G, and B signals.

In addition, when transmitting the MUSE signal via FM satellite broadcasting etc.,
In the emphasis circuit of FIG. 5 (512), FIG. 9(a),
Emphasis and nonlinear processing shown in (b) are performed.

In the de-emphasis circuit of Fig. 6 (604), the de-emphasis circuit of Fig. 9 (
Processing is performed for the characteristics shown in C) and (d), that is, the inverse characteristics to (a) and (b).

For example, in a MUSE encoder, a video signal that changes from white to black to white as shown in FIG. 9(e) has the edge part of the video signal emphasized by the emphasis processing in (a), resulting in the signal waveform shown in (f). (g) by non-linear processing of b)
The signal waveform is as follows. This is FM transmitted, and the received signal waveform (h) is decoded by the MUSE decoder (C).
The emphasis processing and the reverse nonlinear processing of (d) result in signal waveforms a(i) and (j), respectively.

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

The above is an overview of the MUSE method. Next this MU
A device for recording and reproducing SE signals will be explained.

An analog recording method or a digital recording method can be considered as a recording/reproducing device for the MUSE signal, and a magnetic tape, an optical disk, etc. can be considered as a recording medium. this house,
A so-called digital VTR that digitally records on magnetic tape will be described. For example, JP-A-62
-238184 publication (HO4N 5/92) r
There is a MUSE video recording and playback device. This will be explained according to FIG.

The MUSE signal input to the input terminal (901) is band-limited by the low-pass filter (902), and the A
A /D converter (903) converts it into a digital signal. Note that the MUSE signal is transmitted as a sample value, and this sample value must be generated accurately. For this reason, P
A 16.2MH2 sampling clock synchronized with the MUSE signal is generated by the LL circuit (904), and A/D conversion is performed using this clock. M obtained in this way
The USE digital signal is time-base compressed (905), and an error correction code is added to the free time base (906). After that, it passes through a modulator (907), a recording amplifier (908), a switch (909), a rotary transformer (910), and a magnetic tape (912) by a rotary magnetic head (911).
to be recorded.

During reproduction, the signal reproduced by the rotating magnetic head (911) is transferred to the rotating transformer (910) and switched! (909) and is amplified by a reproducing amplifier (913). Demodulate this (91
4) A time axis correction circuit (915) corrects fluctuations in the time axis of the rotating magnetic head. Next, code errors are corrected and corrected (916), and the time axis is returned to the state before recording in the time axis expansion circuit (917). After that, D/Affi exchange (9
18), band-limited by a low-pass filter (919), and output from an output terminal (920).

(c) Problems to be Solved by the Invention When performing FM transmission as described above, emphasis processing is applied to the video portion of the MUSE signal. Therefore, when recording this MUSE signal with a conventional digital signal recording/reproducing device, the video signal from the black level to the white level is recorded with 8-bit precision (-128 to 12
7) To obtain the signal of (h) as 10 and y)? '#Every time(
-512 to 511), and the number of quantization bits is 1.
A 0-bit digital signal must be recorded.

That is, in general, in order to obtain a video signal with N bit precision (N: an integer), a quantization bit number of N+2 bits is required. This poses a problem as the recording bit rate increases in digital signal recording/reproducing devices.

(d) Means for Solving the Problems In the present invention, the emphasized MUSE signal is recorded after de-emphasis processing. Specifically, MUSE
Quantize the signal with M bits, then de-emphasize,
By bit conversion processing, the data is converted into N (MAN) bits and recorded. In another configuration of the present invention, the AM mode MUSE signal is forcibly output during playback.

(E) Effect By recording and reproducing the MUSE digital signal after de-emphasis processing, it acts to reduce the number of quantization bits required for a predetermined S/N of the video signal. In other words, the recording and write rates in the MUSE digital signal recording/reproducing apparatus are reduced. Also, during playback, the output is forced into AM mode, so the V
No emphasis circuit is required for the TR.

(F) Embodiment As an embodiment of the present invention, a digital VT that records and reproduces digital signals on a magnetic tape using a rotating magnetic head will be described.
R will be explained according to the block diagram of FIG.

The MUSE signal input to the input terminal (101) is band-limited to 8.15MHz by a low-pass filter (102),
It is converted into a digital signal by an A/D converter (103).

At this time, the PLL circuit (104) generates a 16.2 MHz sampling clock synchronized with the MUSE signal, and samples are performed using this clock. Also, based on the clamp level of the MUSE signal, the 10-bit 2° S
It is assumed that A/D conversion is performed to a conbriment (two's complement) code.

After that, the separation circuit (105) separates the video signal, audio signal,
Separate control signals. Then, the de-emphasis circuit (106) performs de-emphasis processing on the video signal, further performs inverse gamma correction processing for the transmission line (140), and then converts the signal from 10 bits to 8 bits in the bit number conversion circuit (107). Perform the conversion.

As shown in FIG. 9(j), the video signal after de-emphasis processing falls within the level of -128 to 127, so l
To convert from O pit to 8 bits, simply take out the most significant sign bit and the least significant 7 bits.

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

The parity generation circuit (111) generates vertical parity and horizontal parity for the audio and video data stored in the memory (110) so as to constitute the correction block shown in FIG. ). As shown in Figure 2, the correction block is horizontally n
It is composed of 1 word of audio, n words of video, n words of horizontal parity, and vertically composed of m1 words of audio or video and m word of parity. These correction blocks constitute one track, and one field of video, audio, and control data is recorded using L trunks.

After parity generation, audio data, video data, control data, and parity are sequentially read from Memo'J (110) and input to the frame synthesis circuit (112) while being distributed to each channel. Here, Figure 3 (a
) Construct a frame like the one shown. 11 words of synchronization signal, 2. Word address signal, (n 1+ n t
+ n I) One frame is composed of words of video data, audio data, and parity. That is, a synchronization signal and an address signal are added to the horizontal portion of the correction block shown in FIG. 2, and the signals are sequentially sent out. At this time, a synchronization signal generation circuit (113) outputs a synchronization signal, and an address signal generation circuit (114) outputs an address signal.

On the other hand, as for the control signal, as shown in FIG. 3(b), a frame is constructed by adding 21 words of a synchronization signal, an address signal i, and a word to the beginning. Add correction parity or perform multiple writing as necessary.

Further, in a digital VTR recording with a rotating head, a preamble section and a postamble section are provided at the head switching section, that is, at both edges of the recording track. This is due to margins when switching heads, pull-in time for clock regeneration, absorption of cylinder rotation jitter, etc. The preamble and postamble signals are normally signals with a constant frequency that is the highest recording frequency of the digitally recorded signal or an integer fraction thereof. These signals are generated by a preamble/postamble signal generation circuit (115), and this signal and the output signal of the frame synthesis circuit (112) are synthesized by a synthesis circuit (116). Thereafter, it is modulated by a digital modulation circuit (117) and amplified by a recording amplifier (118). The switching circuit (119) switches between recording and playback, and during recording, it switches the two-channel signal from the recording amplifier (118) into two systems depending on the rotational phase of the rotary head, and sends the signal through the rotary transformer (120). and records on a magnetic tape (122) with a rotating magnetic head (121).

At this time, the signal format of the track recorded on the magnetic tape is as shown in FIG. 81 frames of preamble signal are recorded on the magnetic tape entrance side, and then S
, frame control signal, S, frame audio/
A video/parity signal, a control signal for the S frame, and a postamble signal for the S frame are further recorded.

During playback, signals recorded on the magnetic tape (122) are read out by a rotating magnetic head (121), input to a playback amplifier (123) via a rotating transformer (120) and a switching circuit (119), and amplified. Thereafter, a waveform equalization circuit (124) compensates for the characteristics lost in the magnetic recording/reproducing system, and tarock generation (125) is performed based on this reproduced signal. Using this tarock, the signal after waveform equalization is demodulated into the original digital signal by a demodulation circuit (126). and,
Synchronization detection (127) is performed, and based on this synchronization detection signal, data is separated in a synchronization separation/S/P conversion circuit (128) and S/P (serial to parallel) converted. This data is written into the memory (129) in word units. The error correction/correction circuit (130) uses a memory (129).
) performs error correction or correction processing on the video, audio, and control signals written in the video, audio, and control signals.

These corrected/corrected video, audio, and control signals are read out from the memory (129). For video signals, the bit number conversion circuit (131) converts 8 bits to 1 bit number.
After conversion to 0 bits, gamma correction for the transmission path is performed (139), and emphasis processing shown in FIGS. 8(a) and 8(b) is further performed.

The audio signal is converted from a binary code to a ternary code by an audio signal processing circuit (133), and a ternary level represented by 10 bits is assigned to the ternary code. Furthermore, a control signal processing circuit (134) assigns a binary level represented by 10 bits to the control signal. After performing these processes, the synthesis circuit (135
), synthesize it into the signal format shown in Figure 7, and perform D/A conversion (
136), band-limited by a low-pass filter (137), and output from an output terminal (138).

As explained above, the digital VT of the embodiment of the present invention
In R, for recording and reproducing MUSE signals, video signals are
This solves the problem of having to record and reproduce a signal with a quantization bit count of 10 bits in order to obtain bit precision.

Note that this embodiment is an example of a digital VTR that records a MUSE signal and outputs a reproduced signal as a MUSE signal. Therefore, in order to display the reproduced signal on a monitor, a high-definition signal must be obtained via a MUSE decoder and then connected to a high-definition monitor. Apart from this, it is also possible to consider an apparatus that combines a digital VTR (MUSE) decoder and obtains a high-definition signal directly from a reproduced signal.

In this case, the digital VTR in Figure 1 and the MUSE in Figure 6
In the decoder, the output of the separation circuit (603) and the output of the de-emphasis circuit (604) in FIG. 6 can be replaced with the output of the memory (129> in FIG. 1. ~ (137) circuit and (6 in Fig. 6)
The circuits 01) to (604) become unnecessary.

In the above configuration, the MUSE signal is output as the output of the VTR. Therefore, in the VTR playback circuit,
An emphasis circuit (132) similar to that provided in the encoder (see Figure 5) is required. Therefore, the circuit scale becomes large.

FIG. 10 takes this point into consideration. Components that are the same as those in FIG. 1 are designated by the same reference numerals, and explanations thereof will be omitted.

Although omitted in the configuration of FIG. 1, the state of the 20th bit (“IJ or “
0”)), the control signal processing circuit (109)
), the video signal processed by the de-emphasis circuit (108) or the unprocessed video signal (1
43) is provided. 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. In the case of AM modulation, the 20th bit becomes rlJ and selects a video signal that is not subjected to de-emphasis processing.

This signal selection circuit (141) includes an inverse gamma correction circuit (Fig. 1 (140)) and a bit conversion circuit (Fig. 1 (140)).
07)), therefore, performs inverse gamma correction and bit conversion on the selected signal and stores it in memory (110).
Output to. The subsequent recording and reproducing operations are substantially the same as in 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 (this is done in the control signal processing circuit (134)). ). This allows the monitor TV to be supplied with playback output.
The decoder processes the video signal without de-emphasizing it.

In the above explanation, the control signal is set to a non-emphasis state during playback, but the same setting can also be made before recording on a recording medium (this is done by the control signal processing circuit (109)).

In the configurations shown in FIGS. 1 and 10, de-emphasis processing is performed after A/D conversion, but a configuration in which de-emphasis is performed in the analog signal state and A/D conversion is also possible. In this way, the amplitude of the signal to be A/D converted becomes small, and the number of required bits can be reduced.

(g) Effects 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.

Furthermore, since the output signal during reproduction is forcibly set to the AM mode without emphasis, the emphasis circuit can be omitted.

[Brief explanation of the drawing]

1 and 10 are block diagrams showing embodiments of the present invention,
Figures 2, 3, and 4 are explanatory diagrams for explaining the format of recorded signals, Figure 5 is a block diagram showing the MUSE encoder, Figure 6 is a block diagram showing the MUSE decoder, and Figure 7 is a block diagram showing the MUSE encoder. The figure is an explanatory diagram showing the transmission format of the MUSE signal, Fig. 8 is an explanatory diagram of emphasis and de-emphasis operations, Fig. 9 is a block diagram showing a conventional MUSE VTR, and Fig. 11 is an explanatory diagram of the control signal. be. (103)...A/D converter (106)...
・De-emphasis circuit (107)...Bit conversion circuit (134)...Control signal processing circuit 2nd
Figure 3 Figure 4

Claims (3)

[Claims] (1) A digital video signal recording and reproducing device that de-emphasizes an emphasized and transmitted video signal to reduce the number of bits required for recording. (2) MU generated by band compression of high-definition signals
The MUSE signal, which is an SE signal and has been subjected to emphasis processing for FM transmission, is set to M bits (M is a natural number).
A digital recording and reproducing device that performs de-emphasis processing on this M-bit MUSE digital signal, converts it to N (M>N) bits, and records the signal. (3) MU generated by band compression of high-definition signals
1. A digital recording and reproducing device for recording and reproducing SE signals, characterized in that an emphasized MUSE signal is recorded after being de-emphasized and output in AM mode during reproduction.