JPS6051391A - Method of encoding and decoding color television signal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to the transmission and reception of component video signals, and relates to the transmission and reception of component video signals.
) This relates to a technique for scrambling (adding changes to prevent eavesdropping, etc.) a video signal and unscramming/I/(returning it back to its original state).

[Background of the invention]

In cable television, satellite communications, subscriber broadcast television, etc., it is desirable to encode television signals for secure transmission. Generally speaking, conventional coding schemes can be said to be either amplitude-modified or rf8#i-approximately 8#i-modified. The amplitude encoder C (hereinafter referred to as an encoder) is, for example, one that changes the amplitude of a horizontal or vertical synchronization pulse, or one that modulates a video signal with an encoded waveform (for example, a sine wave). Another advantage is that the decoder (hereinafter referred to as decoder) is relatively simple and inexpensive. The disadvantage of this high-stakes encoding method is that, generally speaking, the code is relatively easy to understand and read, thus creating the possibility of a rack market for illegal decoders. From a technical point of view, the amplitude distortion imparted to the video signal cannot be completely removed by the decoder, and strict decoder adjustment is required to reduce the remaining distortion in the decoded signal to an acceptable level. Other problems associated with amplitude-varying cramblers include reduced signal-to-noise ratio and loss of dynamic range.

A time sequence changing encoder reorders the sequence of video signals into a non-standard signal sequence. This non-standard sequence can be made highly flexible by random changes. These types of encoders include those that reverse the sequence of picture elements (pixels) within a horizontal line, and those that reverse the sequence of pixels within a horizontal line.
those that vary within the field, or those described in U.S. Patent No. 4.
070,693, which changes the position or rearranges the segments that make up each line of the video signal.

U.S. Patent No. 4. The method described in O'70,693 unpulses one line of video signal at a time (
In other words, it is a method (intra-line scrambling), but the line order is changed within a group of lines (interline scrambling/l')
Compared to the ffl encoder, it has the advantage that less memory is required for the encoder and decoder. Briefly, in this patent scheme, each active line of the composite video signal is "rotated" about a predetermined point that varies randomly over time. This rotation code itself does not directly indicate the rotation center point. It is used to synchronize the random number generator in the decoder with a similar random number generator in the encoder to provide confidentiality regarding the center of rotation.

[Summary of the invention]

This invention applies a pixel-in-line rotational encoding method to a conventional composite video signal, and the resulting code can be applied to a video signal in the so-called "M A C (Multiplexed Analog Component)" video transmission format. This was done with the understanding that it would be relatively easy to decipher when applied.

In the MAC video transmission system, a color video signal is transmitted over a channel (eg, a satellite transponder, a cable system, a broadcast system, a VTR, etc.) using serially transmitted time-compressed analog components. The serial transmission method is preferable because it requires only one channel. Color signals (e.g. YSR-Y and B-Y; Y, U and V, Y,
The use of time-compressed components representing I and Q; or R, G and B, etc.) provides a good reduction in cross-steering between the luminance and chrominance components. In this regard, U.S. Patent No. 4,376.957 dated March 15, 1983 and U.S. Patent Application No. 509,786 dated June 30, 1983 (June 2, 1983)
Please refer to the corresponding Japanese application dated September 9, 2013.

The purpose of this invention is to obtain the advantages of the intra-fin pixel rotational encoding method in a multiplexed analog component (MAC) type video transmission method without losing encoding confidentiality, as will be described later. .

A method according to the invention for encoding a television signal for transmission comprises a source of a television signal to be encoded, each having lines comprising a luminance signal and at least one chrominance component; is provided. First and second signal paths are provided for selectively coupling the luminance and chrominance components, respectively, to an output terminal during a selected non-overlapping period [1C1]. The luminance component of the first signal path is subjected to a given (7) time compression, and the chrominance component of the second signal path is subjected to a greater amount of time compression.The signal sequence of the luminance component in the first signal path is The chrominance component signal sequence in the second signal path is rotated independently, so that the luminance and chrominance components are rotated independently of the chrominance component signal sequence in the second signal path, so that these luminance and chrominance components in the encoded line of the television signal produced at the output terminal are When the temporal position of the component is changed, it is encoded without ('?)-1.

[Detailed explanation]

Figure 1A is a simplified illustration of one fin of a two-component MAC waveform. This is the signal clamp level. In the two-component system, the luminance signal (!l: ``1 horizontal line with two chrominance components equal to about 63 μs)
Unlike the 3-component J method that is transmitted during the period, the U color component and V color component are transmitted alternately on one line. Part B
corresponds to the clamp level period between the chroma component (U or ■) and the luminance component Y.

Figure 1B shows the effect of "rotation", that is,
The result of rotating the signal component of FIG. 1A around point K is shown. Parts A and B are the starting points of the line (arbitrary reference point Tl)
Note that the shift with respect to VC directly indicates the rotation of the picture element (V) of that line. More specifically, the zero point during rotation in FIG. 1A is sandwiched between points N and O in the Y signal.

Once the rotation is learned (FIG. 1B), a new line begins at point O of the Y signal and proceeds to points P, M, and N as shown, until a new "rotation" of the line to be transmitted is established. A signal sequence is formed.

The problem shown in Figures 1A and B was subjected to rotational processing by simply timing from the last horizontal sync pulse (not shown) to one of the easily distinguishable clamp level periods A and B. This means that the degree of rotation of the signal components of the line can be easily determined.As a result, this scramble code is easily discovered, facilitating the so-called black market of pirate decoders. This is reflected in the aforementioned U.S. Patent No. 4. It has been shown that the intra-line pixel rotation scheme, which is very effective in composite video signal transmission schemes of the type described in O'70,693, is not effective in MAC type video signal transmission.

FIGS. 2A and 2B are video signal lines similar to FIGS. 1A and 1B, illustrating the line-to-line rotational encoding method of the present invention. As is clear from this figure, the line before encoding (
Figure 2 A) and the fin after encoding (i.e., after rotation processing) (
Clamp level periods A and 1B in FIG. 2B) do not contain any information indicating the degree of rotation. That is, clamp level portions A and B have not been shifted and have not undergone any changes due to the rotation process. This desirable result can impart a high degree of security to the encoded signal. This effect is obtained by rotating each of the components separately about their respective centers of rotation (K and N'), according to the invention of .

If you want to take this principle further and apply it to a three-component method,
Ingredients (for example, Y1, Q, ; Y, 0.V; Y, R-
4, B-Y, etc.) with its own rotation center point (
K, K/ and K") are rotated individually.

3A and 3B illustrate the principles of the invention in a three-component M
Details of an embodiment applied to an AO format video transmission system will be shown. Same as in the example of Fig. 2 A and B (10), "signal flag" (clamp level/l') u
, the signal before scrambling (after Anne Crumple) (third
There is no constant discernible pattern that occupies the same position in the scrambled signal (Fig. 3B) as in Fig. A) on the basis of which the signal can be unscrambled. .

In this method, the unscrample waveform (Figure 3A) is -
Horizontal synchronization pulse (starts with E(S) of 40 tRE units,
It is followed by a timing signal loop) (T).

Berth I-T has a peak of 120~+20t REF.
It has a peak value and is used in the receiver/decoder to synchronize the phase-locked loop (PLL) that provides the decoder timing signal, which is different from the normal color burst signal used in composite television signal transmission. do not have.

After the timing component, the luminance component Y.

The number of RY color difference components and the number of B-Y color difference components follow in this order. However, the order of the components is not critical to this invention. What is important here is that each component (11) has a separate center of rotation, that is, 1 for Y,
The point rotated about 2 for E-YK and 3 for B-Y and the clamp level in the encoded (scrambled) signal (Figure 3B) are All are consistent with the corresponding levels in the uncoded signal (Figure 3A).

More specifically, the uncoded component Y starts at point A, has 1's around the rotation center at positions B, B', and ends at point C. When component Y undergoes rotation processing, the rotational component becomes point B/
start from. This is followed by part B/ to point C1/ and then part A-B. Therefore, the component Yl-I, in this example, begins at the 37-0 portion, followed by point A (starting point of the unencoded signal) and point B. In other words, this rotation process , which places the latter part of the signal part of component Y at the beginning part of component Y in the encoded signal, but the order of the pixels in each of the rotated signal parts does not change. B-Y have their respective centers of rotation. All clamp levels (e.g., tJf,

It will be seen that the signals (RE and +50THE) retain exactly the same positions as in the component signals before encoding.

The principles of the invention have general application in MAC format video transmission systems. Figure 4 is the aforementioned U.S. Patent Application No. 50.
9,786, which describes the discrete component rotary encoding method of the present invention as applied to a MAC transmission encoder of the type described in US Pat. No. 9,786. The system of the above-mentioned US patent application is a single channel system in which components Y, R-Y and B-Y are transmitted during each line.

The encoder includes a component video signal source 400, which inputs a luminance component Y to an analog-to-digital/I/(A/D) converter 402 and a first color difference component R-4 to an A/D converter 404. , second color difference component B
-Y is supplied to the A/D converter 406. signal source 40
0 includes a matrix circuit that converts the R, G, and B outputs of a color camera or other suitable signal source into YlR-Y and BY components, for example. A/D converter 4o
2.4o4 and h(13) 4o6ta, ('AL) can be constructed with a conventional 8-bit flash converter. Such converters are suitable for operation at video frequencies and are well known and commercially available. .

The digital outputs of converters 402, 404 and 406 are coupled to multiplexer 410 via each of three signal paths (signal path 1, signal path 2, signal path 3). Multiplexer 41.0 selects each signal path and outputs it to output terminal 40.
Combines with 8. Multiplexer switch) 41
0 receives at its input three signals Y1R-Y and B-Y from each signal path, and sends a selected one of them through a D/A converter 412 coupled in series to a timing and code insertion unit B4VC. Terminal 408 is supplied.

A timing signal source 41G provides a clock signal to the A/D converter (and the rotator (raw data) and time compressor in each signal path, as described below). This timing signal source 416 is further connected to the bus 41
．． Multiplexer switch through 8 l-410
(14) The timing and code insertion unit l-
414, horizontal and vertical synchronization signals (E(S and
), which provides a reference frequency burst signal and a clamp level activation signal. Each of the three signal paths 4 has a rotator and a time compressor (422 and 424 in signal path 1) connected in series.
, 426 and 428 in signal path 2, and 430 and 432 in signal path 3). Both signal sequence rotators and digital and analog time compressors are well known. Examples of these can be found in the aforementioned U.S. Pat. No. 4,070,693.
No. 4.3'76.957 and in U.S. Patent Application No. 509.786. Timing and code inserter 41411-I' Rotator code source 450
are connected to receive rotation code signals 1, K2, and 3 from rotator 422.
426 and 430 are also supplied. Briefly, encoder time compressors 424, 428 and 432 compress video components Y, H-4 and B-Y, respectively, into 2=114:1
and time compression at a ratio of 4:1. The timing mf source 416 operates so that the multiplexer switch 410 sequentially selects the outputs of signal paths 1 to 3 and supplies them to the D/A converter 4]-2.

An inserter 414 adds horizontal and vertical synchronization signals and a reference frequency signal under the control of signal fj 416 and also provides clamping.

According to the invention, the rotator code source 450 supplies the signal element rotators 422, 426 and 430 with rotation codes of 1, K2 and 3, and each rotator independently of the other has a Y component in the signal path 1. Rotation is applied to the signal element (signal element) of the RY component in the signal path 2, and to the signal element of the B-Y component in the signal path 3.

As a result, as explained in conjunction with FIG.
There are no signs indicating the position of the component signals in the encoded signal appearing at 08. vessel 414
2 and 3 are supplied to the rotation code Kl (16). The secrecy of the rotation code is guaranteed by the aforementioned U.S. Patent No. 4,
070,693, or the rotation code may be modified by other means (e.g. 1f, another transmission channel, a water-programmed read-only memory, or other secure transmission systems, etc.). ) may also be transmitted. As previously mentioned, it is important to the invention that each transmitted component is rotated or encoded without its time position being changed.

The MAC type video secure encoder shown in FIG. 4 is coupled to a decoder via a satellite communication link, direct cable transmission system, or other suitable communication channel. FIG. 5 is an example of a decoder for the encoder of FIG. 4.

In FIG. 5, the encoded signal is provided to an input terminal 502 connected to a timing signal generator 504, an A/D converter 506, and a rotor code detector 508. The timing signal generator 504 is a phase-locked loop (P
LL) and a counter to generate clock signals for the expander, rotator and digital converter in the decoder in response to the reference frequency component (17) of the input signal being encoded.

Timing signal generator 504 also keys rotor code detector 508 to decode the rotor codes 1, K2, and 3 during the appropriate line periods of the vertical period.

The output of the A/D converter 506 is sent to a demultiplexer (
The demu code (tj-pleXer) is added to the switch unit 510. switch unit 51
0 selects the output of converter 506 to signal path 1, signal path 2, and signal path 3 in synchronization with the transmission of component signals Y, EY, and B-4, respectively, under the control of timing signal generator 504. and supply it. Signal path 1 includes an output coupled to Y component output terminal 54.0 and signal element rotator 5.
A first D/A converter 514 is included having an input coupled to the Y component output of switch unit 1-510 via a series connection of 16 and 1=2 time stretcher 518. Signal paths 2 and 3 include D/A converters 520 and 5.
26, time delay 522 and 528 and time expanders 524 and 530, respectively, are similarly connected (18). However, the time expander for the color difference signals R-Y and B-4 has an expansion ratio l of the Y component expander in signal path 1.
The operation of the component decoder shown in FIG. The presence of rotator code detector 508 and individual component signal element rotators 51G, 522 and 52B. terminal 50
The three rotation codes transmitted during the vertical period of the Kugata signal added to 2 are detected by the rotation code detector 508, and the three component rotators 516, 522 in signal paths 1-3 are detected by the rotation code detector 508.
and 528, these rotators are Y, R-Y
and B-Y signals by rotating each signal floor in a direction opposite to the rotation initially applied to decode the individual Y, R-Y, and B-Y components.

The principles of this invention are described in U.S. Patent Application No. 509,786-3.
The application to the component (Y, RY, B-4) method is only one embodiment of the present invention. Multiplexed analog video (M
In the AY) transmission method, according to the method of giving rotation processing to each of the black (], 9) minance and luminance components, the in-line scrambling characteristic of the component transmission method can be simplified, and as described in @ , a time shift component proportional to the rotation within the line occurs, which eliminates the problem of the time shift required for decoding or the problem of giving a clue about the (':i rotation. In other words, according to the present invention, sequential Component transmission systems are provided with the secrecy of traditional line-based oral synthesis video transmission systems.The principles of the invention have wide utility, can be applied to two or three component systems, and are similar to those described above. , RY, and B-Y components, it can also be applied to components containing Y, (2), and Ql, or Y, U, and V.

[Brief explanation of the drawing]

FIGS. 1A and 1B are simplified waveform diagrams illustrating the intra-line rotational encoding method for MAC format video signals, and FIGS. 2A and 2B are line rotational rotational encoding methods for MAC format video signals according to the present invention. Figures 3A and 3B are simplified waveform diagrams illustrating the application of the principle (20) of the present invention to a video transmission system in which each line contains three components. Figure 4 showing details of
The figure is a block diagram of an example of an encoder embodying the present invention, and FIG. 5 is a block diagram of an example of a decoder embodying the present invention. 400...Color television signal source, 424.42
8.432...Time compressor, 422.426.430
...Rotator, 450...Rotator code source, 408.
.・Output 518.524.530...Time expander, 516.5
22.528...Rotator. Patent Applicant: RCI Corporation Corporation: Satoshi Shimizu and 2 others

Claims (2)

[Claims] (1) providing a signal source for a color television signal to be encoded containing a luminance component and at least one chrominance component in each fin; each of said luminance component and said chrominance component; of,
providing a first signal path and at least one other signal path for selectively feeding an output within a selected non-overlapping time period; in said first signal path.
1. Time-compressing the luminance component by a first predetermined amount, and compressing the chrominance component in the other signal path.
- compressing the time by a second predetermined amount that is greater than the first predetermined amount; a time rotation process to encode each of the luminance and chrominance components without altering their temporal position in the encoded fins of said television signal produced at said output; A method of encoding a color television signal for transmission comprising; (2) decoding a color television signal having a luminance component and at least one chrominance component transmitted in a time-sequential component format, each component being encoded separately by signal elemental transmission processing within that component; providing a first signal path for coupling the luminance component of the television signal to an output during a first time period; at least one other signal path coupled to the output during a second period separated by a predetermined time period during which the television signal is clamped to a predetermined clamp VV/l/VC. 2. Rotating the signal element of the luminance component within the first period and -1-! The reminanne signal is returned to its likely time sequence, and separately, during the second period, the signal element of the ten rominanne components is rotated in a direction such that the chrominance component is returned to its original time sequence. A color television signal decoding method 0 comprising the steps of;