JPH02155386A - Signal decoding method - Google Patents

Abstract

PURPOSE:To prevent generation waveform distortion by decoding a part such as an overlap part and a linear processing part or the like subjected to break processing based on a pedestal level in order to decode a video signal sent by an in-scanning line signal switching processing. CONSTITUTION:A memory controller 7 controls an address of a memory 5 so that a signal read from the memory 5 is descrambled correctly by using the count result form a dot counter 6 counting the in-sccanning line signal and a line counter 8 counting the scanning line and a key data from a scramble data recovery circuit 4. Thus, the signal read out of the memory 5 is as shown in figure (a). The signal is given to a D/A converter 9 and a descramble signal in which the break point processed part is decoded into a pedestal level is obtained from an output terminal 10. Thus, the waveform distortion onto a video signal by the break point processing part is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to scrambling means for CATV and satellite broadcasting, and
7. The present invention relates to a signal restoration method for restoring a signal subjected to intra-scanning signal switching.

BACKGROUND OF THE INVENTION In recent years, scrambling processing for converting the time axis of a video signal has been devised (for example, Japanese Patent Application Laid-open No. 171880/1983). A conventional signal restoration method will be described below with reference to the drawings.

FIG. 3 is a waveform diagram showing a conventional signal restoration method. Third
In the figure, (al is the video signal which is the original signal, C1 is the cutting point M of this original signal, M2, M3, M4 is each point of the original signal, (b) is the signal switched within the scanning line. The video signal, shaded areas 01 and 02 are overlap areas, S,
, S2 is the part processed as cutting point processing in the straight line processing section,
(C) shows the restored video signal.

The conventional signal restoration method described above will be explained below. Third
In the figure, the original signal (a) is subjected to time axis conversion at the cutting point CI. With respect to cutting point C1, the period from point M1 to cut rice cake cutting 1 is set as overlap part 01, and the period from cutting point 01 to point M is set as overlap part 02 for the period from cutting point C1 to point M2. , the period from point M3 to cutting point C1 is calculated, and furthermore, as a straight line processing section, Sl
, S2 is added and the intra-scanning line signal is switched (b
). The overlap units 0□, 0□ and the linear processing units S, S2 prevent waveform distortion at the seam C1 of the restored video signal (C) due to waveform distortion in the transmission system and synchronization deviation in the restoration circuit, and improve the restored image quality. This process prevents deterioration.

The video signal (with which the intra-scanning line signal has been switched) is restored to the restored video signal (C). Corresponding to the original signal (a), the point M1 to the cutting point CI to the point M2 are restored, but the overlap portions 01, 0□ and the straight line processing portions S1 and S2 are left as they are and restored.

Problems to be Solved by the Invention However, in the above method, the overlamp parts 0□, 02 and the linear processing parts S, S2 remain in the restored video signal (C), so the decoder side Due to band limitations, etc., waveform distortion occurs at points M11 and M2, resulting in deterioration of the restored video signal.

Means for Solving the Problems In order to solve the above problems, the signal restoration method of the present invention includes:
The pedestal level in the scanning line is detected for the part that was subjected to cut point processing to restore the transmitted video signal after the intra-scanning signal processing has been performed, and the video signal is restored to this pedestal level.

Effect of the Invention The present invention uses the above-described method to restore the video signal transmitted by intra-scanning line signal switching processing by restoring the overlap portion, linear processing portion, etc. that have been applied as cutting point processing to the pedestal portion. As a result, waveform distortion due to these portions remaining in the restored signal does not occur.

Embodiment Hereinafter, a signal restoration method according to an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a waveform diagram showing the restoration method of the present invention. FIG. 1(a) is a video signal in which the intra-scanning signal has been switched, which is an enlarged view of the vicinity of the synchronization signal in FIG. 3(b), and P is Pedestal level detection point, P,, P2. P3. P□ is each point of the video signal,
The rest is the same as in FIG. 3, and (b) is the restored video signal. FIG. 2 is a configuration diagram of a decoder in an embodiment of the signal restoration method of the present invention, where ◯ is an input terminal for a scrambled signal, 2 is an A/D converter, 3 is a timing generation circuit, 4 is a scrambled data reproducing circuit, 5 is a memory, 6 is a dot counter, 7 is a memory controller, 8 is a line counter, 9 is a D/A converter, and IO is an output terminal for a descrambled signal.

What is the signal restoring power of the present invention configured as described above? The decoder of jx will be explained. In Figure 2, input terminal 1
The signal shown in FIG. 3(1), which is a signal in which the intra-scanning line signal has been switched, similar to the conventional example, is input.

The signals are then converted into digital signals by the A/D converter 2 and sequentially input to the memory 5. Further, a signal from the input terminal l is applied to the timing generation circuit 3. The timing generation circuit 3 generates clock and horizontal timing signals necessary within the decoder.

Vertical, etc. timing signals are generated and provided to other parts within the decoder (not shown). The signal from input terminal l is
It is assumed that the vertical retrace period contains key data indicating the contents of the scramble.

Therefore, the key data is reproduced by the scrambled data reproduction circuit 4 from the video signal inputted from the input terminal 1 and is applied to the memory controller 7.

The memory controller 7 includes a dot counter 6 that counts within the scanning line and a line counter 8 that counts the scanning line.
The address of the memory 5 is controlled based on the count result from the scramble data reproducing circuit 4 and the key data from the scramble data reproducing circuit 4 so that the signal read from the memory 5 can be descrambled correctly.

The signal from the A/D converter 2 is similar to that shown in FIG. 3(b), and the vicinity of the horizontal synchronization signal is shown in FIG.
a), and the cut point processing is applied to the overlap portion 0. , 02 and the straight line processing units S, , S2. Point P is a point at a fixed address between one horizontal scanning line and indicates the pedestal level. The memory controller 7 sends the memory 5 to the point M1 in FIG. 3(C).
During the period from point M2 to point M2, a restoration address is similarly issued to restore the signal in FIG. 3(b), and during the period from point P1 to point PZ+point P3 to point P4 in FIG. By outputting the address of point P as the restoration address so that it can be restored to the pedestal level as shown in (g)), the signal read out from the memory 5 becomes as shown in FIG. 3(a). This signal is obtained from the output terminal 1o via the D/A converter 9 as a descrambled signal in which the cut point processing portion is restored to the pedestal level. Therefore, no waveform distortion occurs in the video signal due to the cutting point processing portion.

Effects of the Invention As described above, the present invention restores the portion where cut point processing has been performed to restore the video signal transmitted after intra-scanning signal switching to the bedscale level within the scanning line. By doing so, it is possible to prevent waveform distortion that would occur if the cut point processing portion were left behind.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the signal restoration method of the present invention, FIG. 2 is a block diagram of a decoder in an embodiment of the signal restoration method of the invention, and FIG. 3 is a waveform diagram showing the conventional signal restoration method. 2... A/D converter, 3... Timing generation circuit, 4... Scramble data reproducing circuit, 5... Memory, 6... ...Dot counter, 7...Memory controller, 8...
...Line counter, 9...D/A converter.

Claims (1)

[Claims] It is characterized by detecting the pedestal level within the scanning line and restoring the part that was performed as a cut point process to restore the video signal transmitted after the intra-scanning signal switching has been performed to this pedestal level. signal restoration method.