JP2906412B2 - Transmission method of image data - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to image data in which a carrier signal is modulated with a plurality of image data obtained by sequentially sampling a video signal to transmit the image data. Related to the transmission method.

[Summary of the Invention]

The present invention provides a method of transmitting image data by modulating a carrier signal with a plurality of image data obtained by sequentially sampling a video signal, wherein each of the plurality of image data is By transmitting the image data by AM modulating the carrier signal with the image data so as to sequentially correspond to the half cycle of the carrier signal, the transmission speed and the recording density of the image data can be doubled as compared with the related art. The present invention provides a method of transmitting image data that can be performed.

[Conventional technology]

Conventionally, when an analog signal such as an audio signal is transmitted through AM modulation (amplitude modulation), a transmission method shown in FIG. 7 is used.

In Figure 7, the input signals S ₁ has sample-and-hold circuit 2 having the illustration of waveforms input to the input terminal 1, by being sampled and held by the period T, the sample data a as illustrated, b, c ... The signal S ₂ consisting of
Is obtained. The signal S ₂ is supplied to the modulation circuit 3, the carrier frequency f _c supplied from the input terminal 4, by modulating a carrier signal S _c with period T, the signal S ₃ which is modulated as shown can get. This signal S ₃ is the carrier signal
For one period T of S _c, the sample-hold circuit 2 of sampled sample values a, b, c is in the form of assigned respectively. That is, a size that the amplitude of the positive half cycle and negative half cycle of the carrier signal S _c is corresponding to one of the sample values.

The modulated signal S ₃ is supplied to a demodulation circuit 5 on the receiving side to obtain a signal S ₄ shown in the figure. The original signal S ₁ is demodulated by passing the signal S ₄ through a low-pass filter 6. And output to the output terminal 7.

Although this prior art has assigned one cycle T of the carrier signal S _c for one sample value, n times the carrier signal S _c for one sample value (n = 1, 2, 3 ... ..) May be assigned.

[Problems to be solved by the invention]

Since the conventional AM modulation is performed as described above, the sampling frequency of the signal S ₂ can not modulates be below the carrier frequency f _c. The carrier frequency f _c is limited by the characteristics of the transmission path or the recording medium of the signal. Therefore, when transmitting sample data by AM modulation, the data transmission speed and the recording density are limited by the characteristics of the transmission path and the recording medium. For this reason, for example, when image data obtained by sampling a video signal is AM-modulated and recorded on a magnetic tape, the recording time is extremely long.

[Means for solving the problem]

In the present invention, in the image data transmission method in which a carrier signal is modulated with a plurality of image data obtained by sequentially sampling a video signal and the image data is transmitted, each of the plurality of image data is The image data is transmitted by AM-modulating the carrier signal with the image data so as to sequentially correspond to the half cycle of the carrier signal.

[Action]

Since the image data for a certain pixel has a correlation with the image data for the surrounding pixels, even if the image data is transmitted between a plurality of devices by associating one image data every half cycle of the carrier signal, the image data is transmitted without any trouble. You.

〔Example〕

FIG. 1 shows an AM modulation system for implementing the transmission method of the present invention, and the same parts as those in FIG. 7 are denoted by the same reference numerals. In this embodiment, input signal S ₁ is the case of the video signal.

In FIG. 1, a video signal input from an input terminal 1
S ₁ by being sampled with a period of T / 2 by the sample-and-hold circuit 2, respectively one of the image data a, b, the signal S ₂ consisting of c ...... obtained for one pixel. In the modulation circuit 3, by AM modulate a carrier signal S _c of the carrier frequency f _c by the signal S _2, the signal S ₃ is obtained which is modulated. This signal S ₃ is, as shown, a carrier signal S _c
, Respectively, correspond to the image data a, b, c,..., And the amplitude level in each T / 2 period is the image data a, b, c,.
It is the size corresponding to ... That is, the positive half cycle to the image data a signal S _3, c, is e ...... corresponding, image data b, d, is f ...... corresponds to a negative half cycle. Thus, as the modulation circuit 3, that is configured to invert the input signal S ₂ in the negative period of the carrier signal S _c which is synchronized with the input signal S ₂ is used. By the signal S ₃ is to be subsequently example supplied to the demodulation circuit 5 composed of a full-wave rectifier circuit, the image data a, b, c ...... signal S ₄ which are arranged to obtain every T / 2 By passing this signal S ₄ through the low-pass filter 6, the original video signal S ₁ is obtained at the output terminal 7.

According to the above, as compared with the conventional method of FIG. 7, while using the same carrier frequency f _c, the image data a, b, c ......
It is clear that the transmission speed of the data is doubled.

For example, the audio signal is AM-modulated by the above-described method, and the modulated signal (the signal S _{3 in} FIG. 1) is recorded on a magnetic tape, and the signal is recorded using a signal source, a recording / reproducing device, a monitor device, or the like. Can be configured. Such a system is described, for example, in FIGS.
This is shown in the figures and will be described later in detail with reference to these figures. In this case, in order to generally the ground potential of the devices are different, the use of modulation scheme of FIG. 1, for example, as in the Figure 2, the level V ₂ and the width of the level V ₁ of the data b of the data a the case had different, equals substantially V ₃ data a while to be transmitted between devices, b are averaged, precise transmission of data becomes impossible. Therefore, conventionally, as the signal S ₃ of FIG. 7, positive and negative half cycles of it was necessary to transmit a signal having the same level with respect to the center level.

On the other hand, in the case of the present invention, image data is transmitted, and in general, image data of one pixel and each image data of pixels around the pixel (data on both sides of a certain image data in the horizontal direction, 1 Since the data before and after the line, the data before and after the frame, and the data before and after the one field) are correlated with each other, the levels V ₁ and V ₂ of the data a and b are rarely greatly different from each other as shown in FIG. Even if the modulation scheme shown in the figure is used, there is substantially no problem.

Also, as shown in FIG. 2, the levels V ₁ ,
If V ₂ were significantly different, each data balance correction, substantially equal signal is positive and negative levels may be Do what to be transmitted with respect to the center level. FIG. 3 is a table showing an example of a correction value when the above-described balance correction is performed.

In FIG. 3, each of image data a and b has 4 bits,
That is, it is assumed that the brightness is represented by 16 gradations. Further, the area indicated by oblique lines is an area where no correction is performed because the difference between the two data a and b is small. In addition to the above, there is an area where the difference between the two data a and b is “2” or less (for example, a: b (or b: a) is 5: 6, not shown). 5: 6,
5: 4, 5: 3, etc.). The other areas are correction areas, and the data a and b are each subjected to balance correction to an average value of a = b = (a + b) / 2.

FIG. 4 shows an ADBC circuit (automatic data balance control circuit) 9 for performing the above-mentioned correction.

In FIG. 4, input data a and b are applied to a ROM 11 and shifted one bit by a latch circuit 10.
Is added to Therefore, for example, when the data b is directly applied to the ROM 11, the data a is applied from the latch circuit 10 to the ROM 11. The ROM 11 stores the data of the correction table shown in FIG. 3. The correction values are read using the input data a and b as addresses, and the corrected data a and b are read. The read correction data is converted into serial data by the parallel / serial conversion register 12. The serial data is then supplied to the input terminal 1 shown in FIG. 1 after D / A conversion.

Next, a description will be given of an embodiment of a system for recording a still image signal and an audio signal on an audio magnetic tape using the AM modulation method shown in FIG.

FIG. 5 shows an embodiment of a recording system in which one frame or one frame obtained from a signal source
The still image signal of the field is supplied to the encoder 16 through the video amplifier 15. At the same time, an audio signal corresponding to the above-mentioned still image signal obtained from the signal source 1 is added to the head 18 through the audio recording amplifier 17, so that the audio signal is recorded on the audio track of the magnetic tape 19. In this case, the audio signal is recorded on, for example, an R channel track among the two L and R2 channel stereo tracks formed along the longitudinal direction of the tape 19. And the track L channel still image signal S ₃₃ which is AM-modulated is recorded by the head 20.

The still image signal supplied to the encoder 16 is applied to a decoder 21 to demodulate the R, G, and B primary color signals, and is applied to a sync separation circuit 22 to separate the sync signal. The three primary color signals of R, G and B demodulated by the decoder 21 are A / D
The sampling pulse obtained from the PLL circuit 24, which is applied to the converter 23 and driven by the separated synchronization signal, is converted into a 4-bit, 5-bit, and 3-bit digital signal, respectively. The digital three primary color signals R, G, B
Is written into the memory 25 having a capacity of one frame or one field. Writing and reading of the memory 25 are controlled by a memory controller 26 driven by a PLL circuit 24. The digital three primary color signals R, G, and B read from the memory 25 are then supplied to the above-described ADBC circuit 9 in FIG. After being corrected based here on the third diagram of the correction table, is converted into an analog signal S ₁₁ by the D / A converter 27. The analog still picture signal S ₁₁ is a sampling and hold circuit 28
Added to it by being sampled by the sample pulse frequency f _c obtained from the carrier wave generating circuit 29, a first
Figure data a, b, signal S ₂₂ corresponding to the signal S ₂ to the c ...... image data is obtained. This signal S ₂₂ is applied to the modulation circuit 30
Was added to it, by being reversed in the negative period of the carrier signal S _c, AM modulated static image signal S ₃₃ corresponding to the signal S ₃ of FIG. 1 can be obtained. This signal S ₃₃ is a video recording amplifier
Tape 19 is applied to head 20 through 31
For example, on an L channel track.

FIG. 6 shows an embodiment of the reproducing system.
An audio signal reproduced by the head 18 from the channel track is supplied to a monitor device 34 through an audio reproduction amplifier 33. On the other hand, the still image signal S ₃₃ from the L-channel track reproduced by the head 20 of the tape 19 is added to the A / D converter 37 of the decoder 36 through a video reproducing amplifier 35, it is converted into a digital signal. This digital signal is applied to the controller 38, where R,
G and B three primary color signals are obtained, and these three primary color signals are 1
The data is written into the memory 39 having a capacity of one frame or one field. The R, G, and B signals read from the memory 39 are
After being converted into analog signals by the D / A converter 40, the signals are supplied to the monitor device 34. Although not shown, the monitor device 34 is provided with a demodulation circuit and a low-pass filter corresponding to the demodulation circuit 5 and the low-pass filter 6 shown in FIG. 1, and a still image is displayed based on signals demodulated by these circuits. You.

According to the above, the still image signal modulated by AM on the audio magnetic tape 19 can be recorded together with the audio signal at twice the speed of the conventional one. Since a still image signal can be recorded in about 3 seconds, it can be recorded and reproduced in synchronism with the audio signal. In addition, conventional
When the AM modulation method is used, it takes too much time to record and reproduce a still image signal, which makes practical use difficult.

The recording system and the reproducing system shown in FIGS.
And can be integrated. That is, by integrally providing a small display device using liquid crystal or the like with a small audio cassette tape recorder such as a conventional headphone stereo device, a tape recorder with an image can be realized. Further, if the present invention is applied to a still picture videophone or the like, the transmission time of an image can be reduced to half of that in the related art.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the present invention, the transmission speed and recording speed of image data with respect to a transmission path and a recording medium of a limited band can be doubled as compared with the conventional one, although the configuration of the image data transmission circuit can be extremely simplified. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing that different data is transmitted, and the center level changes, and FIG. 3 is a diagram showing correction values when performing balance correction. , FIG. 4 is a block diagram of a circuit for performing balance correction, FIGS. 5 and 6 are block diagrams in a case where the present invention is applied to a recording / reproducing apparatus for a still image signal and an audio signal, and FIG. It is a block diagram of a modulation system. In the reference numerals used in the drawings, 2 is a sample-hold circuit and 3 is a modulation circuit.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 14/00-14/08 H03C 1/00-1/62 G11B 20/00-20/24

Claims (1)

(57) [Claims] An image data transmission method in which a carrier signal is modulated with a plurality of image data obtained by sequentially sampling a video signal to transmit the image data, wherein each of the plurality of image data is A method of transmitting image data, wherein the image data is transmitted by AM-modulating the carrier signal with the image data so as to sequentially correspond to a half cycle of the carrier signal.