JPS61201586A - Scramble transmitter for video image - Google Patents

Abstract

PURPOSE:To eliminate deterioration in TV signal and to record a video image on a VTR or the like by shifting the start position of the video image at each vertical scanning at an interval being an integral multiple of a horizontal scanning period. CONSTITUTION:An NTSC video signal is converted into a digital signal by an A/D converter 1, stored in a memory 2 and subjected to scrambling with respect to time axis at reading. The signal is scrambled by retarding picture data started normally with the 22nd H at each vertical scanning at a time interval of an integral multiple of H (horizontal period) at random or under a prescribed sequence. The reading of the memory 2 is controlled by a memory control circuit 6 receiving delay information from a scramble control circuit 7 for the scanning of scramble and the memory control circuit 6 forms a read address based on a horizontal and vertical synchronizing signal from a synchronous separation circuit 5. The read output of the memory 2 receiving scramble is converted into an analog signal by a D/A converter 3 and led out through a scramble data weight circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video scramble transmission device used in a TV broadcasting system that is viewable only by subscribers.

[Summary of the invention]

By shifting the video start timing of each vertical scan of the television signal at an interval of an integral multiple of the horizontal scan period and transmitting it, it is possible to prevent the image from being seen as a normal image unless it is decoded, and to improve the transmission format of the television signal. This minimizes the distortion and noise experienced in the transmission path, and also allows video equipment with signal processing functions that utilize horizontal correlation to operate normally.

[Conventional technology]

Conventionally, for example, in CATV, television (TV)
One scrambling method uses a transmission method in which the signal is scrambled or shuffled and transmitted so that only specific subscribers can restore the scrambled state and view it. Reversing method (negative/positive reversing method), Reverse scanning method that reverses the time axis of the TV signal, Divide the time axis of the TV signal at any point in the horizontal scanning section and shift that fragment to the subsequent horizontal scanning section method (line shirt ring method: JP-A-59-122
No. 094), etc. have been proposed.

[Problem that the invention seeks to solve]

In the negative/positive reversal type, it is more susceptible to the frequency characteristics of the line and ghosts, which appear as flickers in the reproduced image. In addition, with the reverse scanning method, the time difference between luminance and chroma that occurs during the line is the opposite of normal, and it cannot be corrected on the receiving side, and it is difficult to record with a VTR that performs correction processing such as crosstalk removal using horizontal correlation. become unable. In addition, with the line shuffling method, as mentioned above, horizontal correlation is lost, making it impossible to record on a VTR, and
The TV signal becomes steep at the time-divided position, and waveform deterioration is likely to occur on the transmission path.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a system that does not cause deterioration of TV signals and can be recorded on a VTR or the like.

[Means for solving problems]

As shown in FIGS. 1 and 4, the video scramble transmission device of the present invention uses a memory 2 or the like to change the video start timing of a television signal for each vertical scan at an interval of an integral multiple of the horizontal scan period. The data is transmitted in a shifted manner.

[Operation] Due to the vertical vibration of the image in the vertical scanning period, it will no longer be visible as a normal image unless it is decoded. On the other hand, changes in the transmission format of television signals have been kept to a minimum.

〔Example〕

1 and 2 show an embodiment of the video scramble transmission apparatus of the present invention, in which FIG. 1 shows an encoder at the transmission input end, and FIG. 2 shows a decoder at the transmission output end. The NTSC video signal shown in FIG. 3 is converted into a digital signal by an A/D converter 1, stored in a memory 2, and subjected to scrambling on the time axis when read out.

As shown in Figure 4, scrambling is performed by delaying the image data, which usually starts from the 22nd H in each vertical scan, in a random or fixed sequence for each vertical scan by a time width that is an integral multiple of H (horizontal period). It will be done. That is, as shown in FIGS. 4A to 4E, the image data is delayed by 2H so that the image data starts from 24H on the 1V, the 2V starts from 25H, the 3V starts from 23H, the 4V starts from 26H, and the image data starts at 5V.
Visually, it is delayed as follows from 22H.

Reading of the memory 2 for scrambling scanning is controlled (addressed) by a memory control circuit 6 that receives delay information (scramble data) from a scramble control circuit 7. The memory control circuit 6 forms a read address based on the horizontal and vertical synchronization signals from the synchronization separation circuit 5.

The read output of the scrambled memory 2 is a D/A
The signal is converted into an analog signal by the converter 3, and is derived through the scramble data superimposition circuit 4. The scramble data superimposition circuit 4 is given scramble data (delay information) for each V from the scramble control circuit 7, and the data is inserted into the vertical blanking section of the video signal, for example.

In the decoder shown in Figure 2, the transmitted video signal is converted into an A/D
The data is stored in the memory 11 through the converter 10, and is descrambled when read from the memory 11. Descrambling is achieved by aligning the start positions of all image data with the maximum delay time as shown in FIG.

Address control for descrambling is performed by a memory control circuit 15 that operates based on scramble data and horizontal and vertical synchronization signals from a scramble data extraction circuit 16 and a synchronization separation circuit 14. The read output of the memory 11 is outputted through the D/A converter 13 as a normal descrambled video signal as shown in FIG.

According to the above-described scrambling method, the image vibrates finely up and down due to vertical synchronization, so non-subscribers who do not descramble the image cannot view it. In addition, since scrambling is performed with a delay that is an integer multiple of the horizontal synchronization H, the deformation of the transmission format is minimal and there is little waveform deterioration.
TR can also be recorded normally.

FIG. 6 shows another embodiment of the decoder. For example, if the scramble delay is 5 types, OH-4H, the video signal is passed through a series circuit of analog delay elements 20a to 20d such as CCD, the delayed video signal is taken out from each tap for each H, and the changeover switch 21 is used to Descrambling can be performed by selecting signals so that the delay times of the signals are aligned. The changeover switch 21 is controlled by a switch control circuit 24 that receives outputs from a synchronous separation circuit 22 and a descrambled data extraction circuit 23. The encoder side can also have a similar configuration.

〔Effect of the invention〕

As described above, the present invention shifts the start position of the video for each vertical scan at an interval that is an integer multiple of the horizontal scanning period, so scrambled transmission can be performed with minimal deformation of the transmission format of the television signal, and horizontal correlation can be reduced. Even video equipment that has the signal processing function used can operate normally.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the encoder of the scramble transmission device of the present invention, FIG. 2 is a circuit diagram of the decoder, and FIG.
5 to 5 are waveform diagrams of video signals, and FIG. 6 is a circuit diagram showing another embodiment of the decoder. In addition, in the symbols used in the drawings, -Memory 3--・------------ D/A converter 4---------- 1---
Scramble data superimposition circuit 5−・−・・−・−・−・
Synchronous separation circuit 6--------------
・Memory control circuit 7・−・−−−1−−−−
---This is a scramble control circuit.

Claims (1)

[Claims] A video scramble transmission device that transmits a television signal by shifting the video start timing for each vertical scan by a time width that is an integral multiple of the horizontal scanning period.