JPS581872B2 - Digital color encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital color encoder that directly converts an image output signal of a color television camera from analog to digital and forms an encoded color television signal through digital operations.

Conventionally, in order to encode a color television signal, a composite color television signal is produced by processing the primary color image signal obtained as the imaging output of a color television camera in the form of an analog signal and frequency multiplexing the carrier color signal onto the luminance signal. This composite color television signal was converted from analog to digital and encoded.

Therefore, an encoder for forming an encoded color television signal has a complex circuit configuration by adding an encoding circuit to the circuit of a conventional color encoder. Because of the processing process, it is difficult to obtain a stable encoded signal, and it is also difficult to perform digital signal processing such as band compression, which is necessary to improve the transmission efficiency of the encoded signal.

An object of the present invention is to form a digital signal directly from the imaging output of a color television camera, perform all the necessary signal processing by digital calculation, and facilitate the signal processing necessary for transmitting the digital signal to ensure stability. The object of the present invention is to provide a digital color encoder suitable for forming encoded color television signals.

That is, the digital color encoder of the present invention has the following features:
The luminance signal is sampled at a sampling frequency equal to three times the frequency of the color subcarrier to form coded luminance signals, each having a phase difference of 120 degrees, the algebraic sum of their respective amplitudes being zero, and The three-phase carrier color signal is sampled in the period of the color subcarrier, the sum of each vector corresponding to the vector of the two-phase carrier color difference signal obtained by quadrature two-phase modulation of the color subcarrier by two color difference signals. A coded carrier color signal is formed by sampling with a phase synchronized with a frequency, and the coded carrier color signal is superimposed on the coded luminance signal to form a coded color television signal. It is something to do.

As mentioned above, the present invention simplifies the circuit configuration by selecting the sampling frequency for encoding a color television signal to be three times the color subcarrier frequency and obtaining a three-phase encoded carrier color signal. , and facilitates the signal processing necessary for digital transmission. Referring to the drawings below,
The present invention will be explained in detail.

As shown in Fig. 1, the carrier color signal of the NTSC color television signal is the three primary color image signals R, G, B output from a color camera and the luminance signal Y composed of these primary color signals.
Two color difference signals R-Y and B-Y of the difference signals with
The color subcarrier is quadrature modulated by an appropriate amplitude ratio of 2
However, in the color encoder of the present invention, the carrier color signal having such a configuration is
As shown in FIG. 2, it is configured to be formed by vector synthesis of three vectors each having a phase difference of 120 degrees.

As is clear from Figure 2, these three vectors are
It is set so that the algebraic sum of the amplitudes of the three vectors becomes zero, and the sum of these three vectors coincides with each vector in the conventional quadrature two-phase modulation shown in FIG.

An example of the configuration of a digital color encoder according to the present invention using such three-phase carrier color signals is shown in FIG.

The digital color encoder of the present invention converts digital luminance signals Y from digital primary color signals obtained by directly A-D converting analog signals R, G, and B as three primary color image signals output from a color television camera into Y= 0.30R+0.59G+0.11B, and then immediately form the baseband composite color television signal M, that is, the subcarrier signals of the second and third terms in the digital primary color signal and the digital luminance signal. hand,
It is digitally combined with a digital luminance signal to obtain an encoded color television signal.

In the configuration example shown in FIG. 3, first, analog three primary color image signals R, G, and B are led to A-D converters 1, 2, and 3, respectively, and the color subcarrier frequency fs from the frequency multiplier circuit 7 is
For example, 1
Pulse encoding of 8 bits per pixel is performed to form an encoded signal in the form of a binary number.

The encoded signals of these primary color image signals are encoded with both words and clocks being synchronized.

Next, the binary numbers of these encoded primary color signals are led to multiplication circuits 4, 5, and 6, respectively, and multiplied by the binary numbers as shown in the figure. Gains of 0.59 and 0.11 times are given to the B signal, respectively.

Here, the relationship between the illustrated binary multiplication coefficient and decimal value is
The following table includes numerical values for multiplication circuits 17 and 18, which will be described later.

These encoded primary color signals given appropriate gain ratios are led to a digital adder circuit 8 to form an encoded luminance signal Y.

On the other hand, digital subtraction is performed by adding the encoded B signal and Y signal and R signal and Y signal to subtraction circuits 9 and 10, respectively, to obtain encoded color difference signals B-Y and RY in the respective subtraction outputs. These encoded color difference signals are then guided to sample number thinning circuits 13 and 14, respectively.These sample number thinning circuits thin out two out of every three sample values of the original encoded signal to reduce the number of samples to 1/1. This is a gate circuit that reduces the number to 3.

Then, the coded color difference signal, which has been reduced in number of samples and made into a coded signal at the sampling frequency fs, is applied to a multiplication circuit 17,
18 and perform the illustrated binary multiplication to form encoded signals corresponding to and, respectively, as shown in the table above.

Therefore, the output signals of the sample number thinning circuits 13 and 14 in the digital calculation described above are broadband color difference signals B-Y,
These are encoded signals in which R-Y is sampled at the sampling frequency fs, and the high-frequency components of these encoded signals are the encoded color difference signal B as a return signal during sampling at the sampling frequency 3fs. It is mixed into the low frequency components of -Y and RY.

The spectra of these mixed signal components have a sampling frequency of 3fs and the mixed signal has a sampling frequency of fs, so the spectra of the original signal and the mixed signal are alternately interpolated by frequency interleaving. /2 offset relationship.

Therefore, in order to remove the false signal spectra mixed in by such aliasing, false signal removal filters 15 are inserted after the sample number thinning circuits 13 and 14, respectively.

These false signal removal filters are, as mentioned above, 1
Since the purpose is to remove mixed signals of a spectral array having a /2 offset relationship, for example, as shown in FIG.
A comb filter constructed by a 1-digit shift circuit 32 of 1 and 2 digits, and performed by digital calculation in the form of low-pass in the vertical spatial frequency domain, which utilizes the difference in polarity of mixed signals between signals in adjacent horizontal scanning periods. It can be made to act as

The encoded color difference signal in the form of and is obtained by adding the BY signal from the multiplication circuit 17 to the binary one-digit shift circuit 19 and further increasing the gain by 1.
/2, and then lead it to the subtraction circuit 20 and addition circuit 21 as shown in the figure, and the output signal of the 1-digit shift circuit 19 is subtracted from the output signal of the multiplication circuit 18 to the output of the subtraction circuit 20. An encoded signal is obtained, and the output signal of the adder circuit 21 is obtained by adding the output signal of the multiplication circuit 18 and the output signal of the 1-digit shift circuit 19, both with negative polarity.

A multiplication circuit 17 obtained by the above digital calculation,
Each output encoded signal (2) of the subtraction circuit 20 and addition circuit 21
, (3), (4) are εjo, ε+j12 shown in FIG.
The encoded signal corresponds to the amplitude value of each vector at the 0° and ε-j120° phases.

Each of the vectors shown in the second diagram is a three-phase representation of the orthogonal two-phase vector of the carrier color signal in the standard color television signal shown in the first diagram. The carrier colored signal component is.

Note that ωs is the angular frequency of the color subcarrier.

Here, since the sum of the values of each equation (2), (3), and (4) is always zero, the output signal 2 of the multiplier circuit 17
A signal obtained by delaying the output signal of the adder circuit 21 by one sample time is added to /3U, and then a signal obtained by delaying the output signal of the adder circuit 21 by one sample time is added to
By adding the signal obtained by delaying the output signal 2/3 of 0 by 2 sample times, the standard color television signal is encoded into a binary number based on the zero level, which is the level of the achromatic carrier color signal. I get a signal.

In order to perform the above-mentioned digital operation, a subtraction circuit 20,
The output signals of the adder circuits 21 are transferred to the shift registers 2 and 21 respectively.
2.23, the phase of the binary coded signal is delayed by two sampling periods and one sampling period, respectively, so that it becomes the phase described above.

These shift registers shift the input encoded signal by 1 sampling period or 2 sampling periods using a sampling frequency synchronized with the input encoded signal, and as described above, obtain an output encoded signal with the required delayed period. be able to.

The encoded signal adjusted to the required phase and amplitude by the above-mentioned digital arithmetic processing is led to the digital addition circuit 24 and added together with the encoded luminance signal Y from the addition circuit 8,
forming an encoded composite color television signal,
In the above signal processing process, all encoded signals are subjected to digital arithmetic processing in the form of parallel codes, so the parallel encoded signals output from the adder circuit 24 are transferred to the parallel-to-serial converter circuit 24.
5 to convert it into a time-series serial encoded signal suitable for digital transmission, and output a standard encoded color television signal for the image signal section at the output terminal 29.

Note that in the configuration example shown in FIG. 3a, the color subcarrier f
s is fixed encoded by the A-D converter 12 and added to the adder circuit 1.
1 is inserted as a burst signal into the encoded color difference signal output from the subtraction circuit 9, and the synchronization signal from the input terminal 27 is fixedly encoded by the A-D converter 28 and sent to the addition circuit 26.
is inserted into the serially encoded signal to complete an encoded composite color television signal in the form of a standard format.

Furthermore, in the configuration shown in FIG. 3a, if a fixed code signal is not used as the synchronization signal as described above, the digital color encoder of the present invention can be configured as shown in FIG. tion signal.

That is, in the configuration shown in FIG. 4, the three primary color image signals R
, G, and B to A-D converters 1, 2, and 3, respectively, and add the encoded binary numbers to multiplier circuits 34, 35, and 36,
For example, as shown in the figure, the binary coefficient is 0.11, that is, 0
．． A digital arithmetic operation is performed to give a gain of 75 times, and a serially encoded color television signal formed by digital arithmetic processing is carried out in the same manner as in the configuration shown in the third figure. If we take a coded signal and add the blanking period part and the image signal part, excluding the synchronization signal period, as a coded signal corresponding to an amplitude of 0.25, the beginning of the synchronization signal waveform is zero, and An encoded color television signal is obtained in which the white peak of the image signal is a binary encoded signal and each bit is all 1.

Note that in the configuration example shown in FIG. 4, the multiplication circuit 17,
The output signals of the subtracting circuit 22 and the adding circuit 23 (not shown) are selectively switched at the sampling period, and are added to the coded luminance signal Y in the adding circuit 24 (not shown) to obtain a parallel coded color television signal. It can also be configured to form.

Next, a fifth example of the configuration of the digital color encoder of the present invention will be described in a case where a luminance signal Y and three primary color image signals R, G, and B are obtained as the imaging output of the camera, such as in a separate luminance type color television camera. As shown in the figure.

In this case, the input primary color image signals R, G, and B are narrowband signals for forming color signals, and these narrowband primary color signals are
-D converters 1, 2, and 3 perform sampling at a sampling frequency equal to the color subcarrier frequency fs to form a coded signal.

The A-D converter 37 is an A-D converter for the luminance signal Y, and converts the luminance signal at a sampling frequency of 3 fs that is phase-synchronized with the sampling frequency in the color signal A-D converters 1, 2, and 3. Sample it to form an encoded signal.

These encoded signals are then subjected to digital arithmetic processing to form an encoded composite color television signal in the same manner as in the above-mentioned example shown in FIG. 3. However, in the configuration example shown in FIG. There is no need to use the sample number thinning circuits 13 and 14 in the configuration example, and the A-D converters 1 and 2
, 3, the coded color difference signals output from the subtraction circuit 20 and the addition circuit 21 are arranged at 1/3 cycle intervals based on the coded color difference signal output from the multiplication circuit 17, and their The periodic signal is combined with the encoded luminance signal Y in the adder circuit 24.

As is clear from the above description, according to the present invention, the following remarkable effects can be obtained.

(1) The three primary color image signals output from a color television camera are each independently and directly pulse encoded, and all are processed in the form of digital signals to obtain the encoded signal of the standard color television signal, so the color encoder All the signal processing circuits can be constructed from digital integrated circuits, and stable circuit operation can be obtained.

(2) To obtain an analog signal from the encoded composite color television signal formed by the encoder of the present invention, the encoded signal can be easily restored to a standard composite color television signal by simply adding the encoded signal to the decoder. .

(3) The encoded color television signal formed by the encoder of the present invention is itself in the form of an encoded signal obtained by sampling phase-synchronized with the carrier color signal of the original signal, so it can be used for band compression, etc. Digital arithmetic processing of the encoded signal can be easily performed, and there is no need to re-phase synchronize the sampling pulse signal during such arithmetic processing.

(4) By decoding the encoded signal, a carrier color signal from which the color signal can be directly demodulated can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a vector diagram showing a carrier color signal of an NTSC color television signal, FIG. 2 is a vector diagram showing a three-phase carrier color signal used in the digital color encoder of the present invention, and FIGS. A block diagram showing a configuration example of the digital color encoder of the present invention and a configuration of a false signal removal filter used in the configuration example, FIG. 4 is a block diagram showing another configuration example of the digital color encoder of the present invention, FIG. 5 is a block diagram showing still another example of the configuration of the digital color encoder of the present invention. 1, 2, 3... A-D converter, 4, 5, 6...
...Multiplication circuit, 7...Frequency multiplier circuit, 8
... Addition circuit, 9, 10 ... Subtraction circuit, 11 ... Addition circuit, 12 ... A-D
Converter, 13, 14... Sample number thinning circuit, 1
5, 16...False signal removal filter, 17,
18...Multiplication circuit, 19...1 digit shift circuit, 20...Subtraction circuit, 21...
Adder circuit, 22, 23...shift register,
24...Addition circuit, 25...Parallel-to-serial conversion circuit, 26...Addition circuit, 27...
... Synchronization signal input terminal, 28 ... A-D converter, 29 ... Encoded color television signal output terminal, 30 ... 1H delay circuit, 31 ... ...
・Addition circuit, 32...1 digit shift circuit, 33・
... Addition circuit, 34, 35, 36 ... Multiplication circuit, 37 ... A-D converter.

Claims (1)

[Claims] 1. A luminance signal is sampled at a sampling frequency equal to three times the frequency of the color subcarrier to form a coded luminance signal, each having a phase difference of 120 degrees, the algebraic sum of their amplitudes being zero, and , the sampling of three-phase carrier color signals corresponding to vectors of two-phase carrier color difference signals obtained by quadrature two-phase modulation of the respective vector sums or the color subcarriers by two color difference signals in the period of the color subcarriers; sampling with frequency and phase synchronization to form a coded carrier color signal;
A digital color encoder characterized in that the encoded carrier color signal is superimposed on the encoded luminance signal to form an encoded color television signal.