JPH0562507B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a video signal recording and reproducing device.

Conventional Structure and Problems When transmitting a video signal, the frequency band of the video signal itself is quite wide, so a wideband transmission path is required, which increases the cost of transmission. In particular, when using satellite communication or handling high-quality video signals, the frequency bandwidth of the video signal itself becomes a big problem. Therefore, various methods are being studied to reduce the frequency bandwidth of a video signal without deteriorating the image quality (or with deterioration within a practically acceptable range).

By the way, as a method for reducing the data amount of a signal, there is a method of removing redundant data in a signal source and extracting and transmitting only the really necessary data, that is, a method called band compression. There are two main types of this method; one is a method that reduces the number of bits required to indicate the pixel level (pixel value), and the other is a method that reduces the number of pixels to be transmitted. Both methods utilize the properties of the video signal and remove redundant components contained in the video signal. Examples of the former method include a differential coding method (DPCM method) and an orthogonal transform method, and examples of the latter method include a sub-Nyquist sampling method.

By the way, the differential coding method (DPCM method) and the orthogonal transform method are usually digitally processed and transmitted in the form of digital data. On the other hand, in the case of the sub-Nyquist sampling method that reduces the number of transmitted pixels, the data is also processed digitally and is usually transmitted in the form of digital data. However, unlike the differential coding method (DPCM method) and orthogonal transform method, when the signal is returned to an analog state after being sub-Nyquist sampled, the frequency band is narrower than the frequency band of the original video signal, and the signal is returned to an analog state. This makes it possible to perform narrowband transmission.

Based on this idea, there have been attempts to transmit video signals in a narrow band, and for example, satellite broadcasting of high-definition video signals is being considered. The frequency bandwidth of high-definition video signals is about 30 MHz, and if left as is, it will end up occupying most of the transmission band of the broadcasting satellite, which is not desirable. Therefore, effective use of broadcasting satellites by transmitting high-quality video signals in a narrow band in the manner described above is being considered.

On the other hand, in such a satellite broadcasting system, a recording/reproducing device is of course essential.
The recording and reproducing device used here records and reproduces a narrowband high-quality video signal.

Next, a conventional example of a video signal recording/reproducing device will be explained with reference to FIG.

FIG. 1 is a block diagram showing a conventional example of a video signal recording/reproducing apparatus. In the figure, 1 is an input terminal, 2 is a recording side processor, 3 and 5 are magnetic heads,
4 is a magnetic tape, 6 is a reproduction side processor, and 7 is an output terminal. A video signal to be recorded is applied to a recording side processor 2 via an input terminal 1. The recording side processor 2 performs clamping, pre-emphasis, clipping, etc.
The data is subjected to predetermined processing such as FM modulation, and recorded onto a magnetic tape 4 via the head 3. On the other hand, during reproduction, the signals recorded on the magnetic tape 4 are restored via the magnetic head 5 and guided to the reproduction side processor 6. The playback side processor 6 performs predetermined processing such as FM demodulation and de-emphasis, and outputs the signal to the output terminal 7.
A video signal is obtained through the .

When the conventional video signal recording and reproducing device as described above is used as the recording and reproducing device for the narrowband high-quality video signal described above, the following problems occur.

In this explanation, we assume that we are dealing with a narrowband signal of a high-definition video signal (hereinafter referred to as "HD signal"). This assumes a method to utilize and reduce the amount of waste. Furthermore, the direction of reduction in the number of pixels is assumed to be the one proposed by the Japan Broadcasting Corporation, and the narrowband HD signal is called a "MUSE signal." The outline of this MUSE signal will be explained later, but although the MUSE signal is narrowband, its frequency band is about 8MHz.
This corresponds to twice the frequency band that can be recorded and played back by conventional video signal recording and playback devices, and it is impossible for conventional video signal recording and playback devices to record and play back MUSE signals from above the frequency band. Furthermore, when restoring the MUSE signal to the original HD signal, the deleted pixels are restored almost to their original state by interpolating the signals of the past three fields and neighboring pixels of the current field. In such a system, if dropout occurs in the signal reproduced from the recording medium, the result is increased deterioration.

Purpose of the Invention In view of the above-mentioned problems, the present invention provides an NTSC
The purpose of the present invention is to provide a video signal recording and reproducing device that is capable of recording and reproducing MUSE signals having a frequency band approximately twice that of PAL signals and reducing image quality deterioration during dropouts. That is.

Structure of the Invention The present invention includes a separator that distributes an applied analog video signal pixel by pixel and separates it into two streams, and a separator that divides the applied analog video signal into two streams, and performs clamping, pre-emphasis, etc. on the separated signal.
A recording-side processor performs FM modulation, etc., and the output of this recording-side processor is recorded on a recording medium, the signal recorded on the recording medium is extracted, and the extracted signal is subjected to FM demodulation, de-emphasis, etc. It has a playback side processor and a synthesizer that combines the outputs of the two lines of playback side processors, and one of the recording side processes the signal a containing the pixels corresponding to the horizontal synchronization signal timing of the above two signals. The switch selects one of these two signals and supplies it to the other recording side processor, and this switch selects the above-mentioned signal a for a predetermined period including the horizontal synchronization signal timing. However, during other periods, the other signal b of the above two signals is selected, thereby realizing efficient and high-quality recording and playback of wide-bandwidth analog video signals (for example, MUSE signals). This makes it possible to reduce image quality deterioration when dropouts occur and to perform highly accurate timing correction.

Description of Examples Examples of the present invention will be described below. FIG. 2 is a block diagram of a device that is the premise of an embodiment of the present invention, in which 8 is an input terminal, 9 is a separator,
10 and 11 are recording side processors, 12 to 15 are magnetic heads, 16 is a magnetic tape, 17 and 18 are reproduction side processors, 19 is a timing corrector, 20 is a synthesizer, and 21 is an output terminal. MUSE to record
The signal is applied to a separator 9 via an input terminal 8. The separator 9 separates the applied MUSE signal into two sequences for each pixel. The method of this separation will be explained in detail later. The two outputs of the separator 9 are supplied to recording side processors 10 and 11, respectively, and are subjected to processing such as clamping, pre-emphasis and FM modulation separately. Recording side processors 10 and 11
The outputs are recorded on a magnetic tape 16 via magnetic heads 12 and 13, respectively. During playback, the signals recorded on the magnetic tape 16 are transferred to the magnetic head 14.
and 15, and apply them to reproducing side processors 17 and 18, respectively. The playback side processors 17 and 18 perform processing such as FM demodulation and de-emphasis on the applied signals and send them to the timing corrector 1, respectively.
Supply to 9. The timing corrector 19 functions to correct the timing difference between the signals output from the reproduction side processors 17 and 18. In this system, during recording, the signals are separated into two systems and recorded on separate tracks, and during reproduction, the signals recorded on the two tracks on the magnetic tape are extracted. However, the expansion and contraction states of the magnetic tape 16 are not necessarily the same during recording and playback, and in compatible playback (when the video signal recording and playback device used for recording and the video signal recording and playback device used for playback are not the same), the recording The relative positional relationship of the two magnetic heads is not necessarily the same between the two magnetic heads in the reproduction case and in the reproduction case. For this reason, the 2
There is a relative timing difference between the system signals, and the timing corrector 19 corrects this timing difference. timing corrector 1
The output of 9 is two signals with no timing difference, and these two signals are combined by a combiner 20, and a MUSE signal is sent out through an output terminal 21.

Here, in the example shown in Figure 2, the frequency band is approximately
The reason why it is possible to record and play back MUSE signals as high as 8MHz is explained below. In a normal video signal recording and reproducing device, the frequency band of the video signal is around 4MHz.
Recording and reproducing MUSE becomes impossible due to the frequency band. Assuming a magnetic tape as the recording medium, the shortest recording wavelength that can be recorded and reproduced is almost constant, so if you want to record and reproduce the MUSE signal as it is, it is necessary to approximately double the relative speed between the magnetic tape and the magnetic head. . Possible methods for doubling the relative speed include doubling the rotational speed of the head cylinder and doubling the diameter of the head cylinder. Since the signal is divided into two parts (segment method), signal processing on the playback side becomes complicated.
On the other hand, in the latter case, since the shape of the head cylinder is different, the mechanical parts of the conventional video signal recording and reproducing apparatus cannot be used at all, and it is necessary to develop all new mechanical parts. As described above, many problems arise when doubling the relative speed. However, MUSE
If the signal is separated into two streams and the frequency band of each signal is reduced by half, it becomes possible to record and reproduce data with the same relative speed as before. If the MUSE signal can be separated into two streams and the frequency band can be halved to about 4MHz, the frequency band is almost the same as that of conventional video signals, so recording and playback will be possible with the conventional head cylinder diameter and rotation speed. Become.

In this way, if the frequency band of each is halved by separating the MUSEB signal into two streams using some method, the conventional mechanism can be used for the most part, and the MUSE signal can be recorded and reproduced without changing the rotational speed or diameter of the head cylinder. It becomes possible. In the embodiment shown in FIG. 2, a separator 9 separates the MUSE signal into two streams, halving the frequency band to approximately 4 MHz, and then processing the signal in recording side processors 10 and 11 and recording it on a magnetic tape 16. From the above explanation, it is possible to record and reproduce MUSE signals with such a configuration.

Next, after briefly explaining the MUSE signal, the operation of the separator 9 shown in FIG. 2 will be explained.

FIG. 3 is a pixel diagram for explaining the MUSE signal. 23 and 25 are odd field horizontal scans, 22 and 24 are even field horizontal scans,
26 to 30 are pixels, respectively. The figure shows consecutive 4
The pixels of each field are shown in the order of n field, (n+1) field, (n+2) field, and (n+3) field. ) field as an odd field. In field n, horizontal scans 22 and 24 are transmitted;
Of the 4 pixels, only the pixels marked with “◎” are transmitted, and “”
The pixel of the mark and “○†a hinoki

Claims (1)

[Claims] 1 As a recording system, there is a separator that distributes the analog video signal pixel by pixel and separates it into two signals, two recording side processors that perform predetermined processing on each of these two signals, and two recording systems. Two systems of playback side processors record the outputs of the side processors on separate tracks and, as a playback system, extract information from the separate tracks and perform predetermined processing on each; and the two playback side processors. a timing corrector that corrects the timing between the respective output signals, and a synthesizer that synthesizes two types of signals output from the timing corrector, and extracts the output of the synthesizer and generates a reproduced video signal. A signal a including pixels corresponding to the horizontal synchronization signal timing of the two signals is supplied to one of the recording side processors, and one of the two signals is selected. and a switch that selects the signal a during a predetermined period including the horizontal synchronization signal timing and selects the signal b, the other of the two signals, during other periods. A video signal recording and reproducing device characterized in that it is configured to select.