JPH0254642A - Sampling clock phase control system - Google Patents

Abstract

PURPOSE:To decode a color television signal synchronously with a color burst phase at a reception section by sampling a phase reference signal synchronously with the color burst of an input color television signal at every prescribed sample of a transmission line clock and transmitting the result. CONSTITUTION:A color subcarrier generating circuit 5 generates a color subcarrier phase synchronized with the color burst of the input color television signal and supplies the signal to a sampling circuit 6 as a 1st phase reference signal. The sample circuit 6 samples the 1st phase reference signal into a multi- value such as 6-bit at every head of the multi-frame. A multiplex circuit 8 multiplexes the sampled PCM signal into a predetermined time slot of the multi-frame of a DS 3. The reception section generates a 2nd phase reference signal phase synchronized with the color burst of the decoded color television signal to apply phase synchronization of the color burst.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an apparatus for sampling and encoding a color television signal and transmitting it, and in particular, it relates to a device that samples and encodes a color television signal and transmits the same. The present invention relates to a sampling clock phase control system that maintains a constant relative phase of a sampling clock.

[Conventional technology]

When encoding and transmitting a color television signal, the transmission path O
When sampling is performed using a sampling clock that is synchronized with the input TV signal without synchronizing with the input TV signal, the method of regenerating the sampling clock in the receiving section is to match the number of sampling clocks in a certain period between the transmitting section and the receiving section. There is a device that synchronizes the frequency so that it matches the
No. ``Sampling Frequency Synchronizer'').

[Problem to be solved by the invention]

In the conventional system described above, the sampling clock of the transmitting section and the sampling clock of the receiving section are synchronized only in frequency, and cannot be synchronized in the phase relationship. In this case, the relative phase of the color burst of the television signal reproduced by the receiver varies in time with respect to the phase of the color burst of the input color television signal of the transmitter due to the phase shift of the sampling clock. There are drawbacks. Therefore, when editing a color television signal using encoded and transmitted signals, it is necessary to perform phase synchronization of color bursts, and a separate device for phase synchronization such as a frame synchronizer is required. .

[Means to solve the problem]

The sampling clock phase control system of the present invention includes a transmitter and a receiver, the transmitter including means for generating a first phase reference signal phase-locked to a color burst of an input color television signal;
means for sampling the first phase reference signal at regular intervals determined by dividing the transmission line clock to obtain a PCM signal; means for sampling the input color television signal using the sampling clock; and means for multiplexing and transmitting the first phase reference signal obtained by using the reproduced sampling clock and the encoded information of the input color television signal sampled by the sampling clock, the receiving section means for decoding encoded information of a color television signal using a color television signal to obtain a color television signal; means for generating a second phase reference signal phase-synchronized with the color burst of the decoded color television signal; means for sampling the second phase modulus reference signal into a PCM signal every cycle in which the phase reference signal is transmitted;
means for determining the cross-correlation between the sampled second phase reference signal and the first phase reference signal; and a means for determining the cross-correlation between the sampled second phase reference signal and the first phase reference signal; and means for generating a sampling clock while performing feedback control so that a constant phase relationship with the signal is maintained.

(Operation) Therefore, the receiving section can decode the color television signal synchronized with the color burst phase of the color television signal of the transmitting section.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the sampling clock phase control system of the present invention, FIG. 1(a) is a block diagram of a transmitting section, and FIG. 1(b) is a block diagram of a receiving section. .

In this embodiment, an NTSC color television signal is A/D converted at a frequency m/n times the horizontal synchronization frequency H, for example, l/n = 682.5, band compression encoded, and the signal is converted along with color burst phase information. The signal is transmitted at a rate of 45 Hb/s, and at the receiving section, the color burst of the decoded color television signal and the phase of the color burst of the transmitted color television signal are set to have a constant phase relationship. The sampling clock is generated by feeding back the phase difference.

As shown in FIG. 1 (al), the transmitter has an input terminal 1,
A/D converter 2, clock generation circuit 39, encoder 4, color sub-gear generation circuit 5, and sampling circuit 6
, a frequency dividing circuit 7 , a multiplexing circuit 8 , and an output terminal 10 . As shown in FIG. 1(b), the receiving section includes an input terminal 11, a separation circuit 12, a clock recovery circuit 13, 18, a mutual phase rIA calculation circuit 14, a sampling circuit 15, and a decoder 16. , a D/A converter 17 , and a color subcarrier generation circuit 19 .

The NTSC color TV signal input to input terminal 1 is A.
The signal is supplied to the /D converter 2, the clock generation circuit 3, and the color subcarrier generation circuit 5. The clock generation circuit 3 generates a sampling clock m/n times the horizontal synchronization frequency fH. This sampling clock is supplied to the A/D converter 2, encoder 4, and other necessary locations. The color television signal is digitized by an A/D converter 2, band compression encoded by an encoder 4, and supplied from the encoder 4 to a multiplexing circuit 8 as encoded information. Color subcarrier generation circuit 5 generates a color subcarrier signal phase-synchronized with the color burst of the input color television signal, and supplies it to sampling circuit 6 as a first phase reference signal. The clock generation circuit 9 is
A transmission line clock of 44.7368H2 is generated, and the frequency dividing circuit 7 divides the frequency into 1/4760, which corresponds to the multiframe period of the third-order group DS3 of the multiplex hierarchy in North America.

The sampling circuit 6 samples the first phase reference signal into multiple values, for example, 6 bits, at the beginning of each multi-frame. The multiplexing circuit 8 multiplexes the sampled PCM signal into a predetermined time slot of the multi-frame of DS3, and multiplexes band compression encoded encoded information 1IIIiD signal etc. into other time slots. turned into
The multiplexed signal is converted to tJ/B and becomes 44,736Hb.
/s is outputted to the output terminal 10 as a bipolar signal.

The clock recovery circuit 'M13 of the receiving section recovers a transmission line clock of 44.7368H2 from the bipolar signal input to the input terminal 11, and supplies it to the separation circuit 12.

The separation circuit 12 performs B/U conversion on the bipolar input signal, and then demultiplexes it from the DS3 frame to generate encoded information, control signals, etc., and the first phase reference signal X↓ and DS3.
The pulse signal indicating the beginning of frame No. 3 is separated and supplied to each section. The clock regeneration circuit 18 generates a sampling clock of an oscillation frequency according to the control signal from the mutual phase 111 nose output circuit 14, and supplies this sampling clock to the decoder 16 and the D/A converter 17. The decoder 16 naturalizes the encoded information to obtain a digital color television signal.

This digital color television signal is converted into an analog signal by a D/A converter 17 and supplied to an output terminal 20 and a color subcarrier generation circuit 19. The color subcarrier generation circuit 19 generates a color subcarrier signal phase-synchronized with the color burst of the decoded color television signal, and outputs the color subcarrier signal to the sampling circuit 1 as a second phase reference signal Yi.
Supply to 5. The sampling circuit 15 samples the second phase reference signal Yi for each beginning of the DS3 frame obtained by the separation circuit 12 and supplies the PCM signal to the cross-correlation calculation circuit 14. The cross-correlation calculation circuit 14 detects a phase shift by determining the cross-correlation between the first phase reference signal and the second phase-shifted reference signal every frame period of DS3.

The cross-correlation coefficient between X and Y↓ is obtained for previous samples, for example, 64 samples. The obtained cross-correlation coefficient is digitally integrated for each frame period of DS3, and after sufficiently smoothing by integration, the integrated value is D/A.
It is converted and supplied to the clock recovery circuit 18. The calculation of the cross-correlation coefficient may be simplified and a value obtained by appropriately normalizing the variance on X and YJ may be used instead. The clock recovery circuit 18 supplies the integrated cross-correlation coefficient signal to a voltage controlled oscillator to generate a sampling clock having a frequency corresponding to the control voltage. That is, the color burst phase signal of the decoded color television signal passes through the D/A converter 17, the color subcarrier generation circuit 19, and the sampling circuit 15, and is subjected to cross-correlation calculation according to the phase fluctuation of the sampling clock. Feedback is provided to circuit 14. Further, the cross-correlation between the fed-back second phase reference signal and the first phase reference signal is calculated, and a signal of the integrated cross-correlation coefficient is sent to the clock recovery circuit 18.

Feedback control is performed in this way, and finally the phase difference between the two becomes 90°, and the cross-correlation coefficient becomes 0.
At this point, the feedback becomes balanced. That is, by performing feedback control and regenerating the sampling clock so that the relative phase of the first phase reference signal and the second phase reference signal is constant,
The phase of the color burst of the reproduced color television signal can be synchronized with the phase of the color burst of the input color television signal of the transmitter.

Note that, as long as the transmission line has a frame configuration, the present invention is applicable not only to DS frames but also to optical transmission lines.

(Effects of the Invention) As explained above, in the present invention, the transmitting section samples and transmits the phase reference signal synchronized with the color burst of the input color television signal at every fixed sample of the transmission path clock, and the receiving section Phase synchronization of the color burst is achieved by regenerating the sampling clock while performing feedback control so that the phase of the color burst of the restored color television signal and the sent phase reference signal have a constant phase relationship. Therefore, there is an effect that the color television signal synchronized with the color burst phase of the color television signal of the transmitting section can be decoded at the receiving section.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are block diagrams showing an embodiment of the sampling phase control system of the present invention. 1.11...Input terminal, 2...A/D converter, 3
．． 9... Clock generation circuit, 5.19... Color subcarrier generation circuit, 4...
Encoder, 6, 15... Sampling circuit, 7...
・Frequency dividing circuit, 8...Multiplexing circuit, 10.20
...output terminal, 12...separation circuit, 13.18...
- Clock regeneration circuit, 14... Cross correlation calculation circuit, 16... Decoder, 17... D/A converter.

Claims (1)

[Scope of Claims] 1. Comprising a transmitting section and a receiving section, the transmitting section generating means for generating a first phase reference signal phase-synchronized with a color burst of an input color television signal;
means for sampling the first phase reference signal at regular intervals determined by dividing the transmission line clock to obtain a PCM signal; means for sampling the input color television signal using the sampling clock; and means for multiplexing and transmitting the first phase reference signal and the encoded information of the input color television signal sampled by the sampling clock, the receiving section transmitting the first phase reference signal by using the reproduced sampling clock. means for decoding encoded information of a color television signal using a color television signal to obtain a color television signal; means for generating a second phase reference signal phase-synchronized with the color burst of the decoded color television signal; A means for sampling a second phase reference signal to generate a PCM signal every period in which the phase reference signal is transmitted, and a means for determining the cross-correlation between the sampled second phase reference signal and the first phase reference signal. means for determining the first phase reference signal and the second phase reference signal by changing the oscillation frequency according to the value of the cross-correlation.
a sampling clock phase control system comprising means for generating a sampling clock while performing feedback control so that a constant phase relationship between the sampling clock and the phase reference signal of the sampling clock is maintained in a constant phase relationship.