JPH05103311A - Subband coding/decoding device - Google Patents

Abstract

PURPOSE:To operate a subband dividing/component filtering without paying attention to a blanking period by performing such format conversion that signals in effective scanning periods before and after the blanking period are substituted for signals in the blanking period. CONSTITUTION:By means of a format conversion circuit 2, such format conversion that video signals in effective scanning periods before and after a horizontal blanking period are substituted for signals in the horizontal blanking period is performed. A subband dividing filter 3 first divides inputted format-converted video signals into two parts in the horizontal direction by means of filter H- LPFs 8 and 9. Then the filter 3 divides the video signals into two parts in the vertical direction by means of filters V-LPFs 12 and 14 and V-HPFs 13 and 15 after down-sampling the video signals with horizontal down-sampling circuits 10 and 11 and outputs subband signals divided into four parts in the horizontal and vertical directions. During the filtering process in the vertical direction, the same processing can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention divides a video signal having an effective scanning period (line) and a blanking period into bands,
The present invention relates to a subband encoding / decoding device for encoding and transmitting.

[0002]

2. Description of the Related Art As a method of compressing a band of an image signal, there is a sub-band coding system in which a frequency band of a video signal is divided for coding. FIG. 8 shows a configuration diagram of this coding transmission device. As a method of dividing and synthesizing frequency bands, QMF
(Quadrature Mirror Filter) and SSKF (Symmetric)
A filter called Short Kernel Filter) is used. On the transmitting side, the horizontal frequency band of the video signal is divided by performing a filtering process on the video signal in the horizontal pixel direction using these filters (horizontal one-dimensional band division). If necessary, the vertical frequency band of the video signal is divided by filtering the video signal in the vertical line direction (two-dimensional band division in the horizontal and vertical directions). After band division, when the video signal of the blanking period of the video signal is not encoded and only the video signal of the effective period is encoded and transmitted, in the above filtering process, the video signal of the effective period is continuous It is necessary to perform filtering processing as. If the video signal of the effective period and the signal of the blanking period are processed as a continuous signal and only the data of the effective period is encoded and transmitted, the signal of the blanking period which is not transmitted on the receiving side. Is replaced with an appropriate value and the filtering process of band synthesis is performed. At this time, a large distortion occurs in the signal after the band combination at the boundary with the blanking period, resulting in a large deterioration in image quality.

In a conventional device, as a method for solving the above problems, control for stopping the filtering process (for example, control for stopping the clock of the filtering circuit) is performed during the blanking period of the video signal. However, this control circuit becomes a complicated circuit when performing horizontal and vertical two-dimensional band division, and becomes a very complicated circuit when performing band division continuously. In addition to this, when this control is performed, the result of the filtering processing of the valid data at the boundary between the valid scanning period and the blanking period can be obtained only after the start of the next valid scanning period. When the signal after band division is coded (especially block coding such as DCT) due to the delay of, a new problem arises in which the coding circuit after band division becomes complicated.

[0004]

As described above, in the conventional sub-band coding / decoding apparatus, the transmitting side processes the video signal in the valid period and the signal in the blanking period as a continuous signal, and When only the data of the period is encoded and transmitted, the receiving side must replace the signal of the blanking period which is not transmitted with an appropriate value and perform the band combining filtering process. Therefore, a large distortion occurs in the signal after the band combination at the boundary with the blanking period, resulting in a large image deterioration. Further, in order to solve this problem, it is necessary to perform control such as stopping the filtering process during the blanking period of the video signal, and especially when performing horizontal and vertical two-dimensional band division, it becomes a complicated circuit. There was a problem that it would end up.

The object of the present invention has been made in view of the above points, and a signal of an effective scanning period separated by a blanking period without performing complicated control such as stopping a filtering process of band division. To provide a circuit that can perform band-division filtering processing as a continuous signal and that does not cause a delay before the result of filtering processing of valid data at the boundary between the valid scanning period and the blanking period is obtained. The purpose is.

[0006]

In order to achieve the above-mentioned object, the present invention performs format conversion in which a signal in a blanking period is replaced with a signal in an effective scanning period before and after the blanking period.

[0007]

As described above, according to the sub-band coding / decoding apparatus of the present invention, format conversion is performed by replacing with the signal of the effective scanning period before and after the blanking period, so that it is not necessary to consider the blanking period. Therefore, it is not necessary to perform complicated control.

[0008]

FIG. 1 shows an embodiment of a subband coding apparatus of the present invention. A description will be given below with reference to this figure. In the first embodiment, the number of sub-band divisions is set to 4 in total in the horizontal and vertical directions. As for the order of the filter, the maximum number of taps of the low pass filter (LPF) or the high pass filter (HPF) is 2N + 1. However,
N is smaller than half the value of the blanking period.

The video signal input from the terminal 1 is format-converted by the format conversion circuit 2 and then output to the subband division filter circuit 3. As the video signal input from the terminal 1, a video signal obtained by A / D converting a luminance signal of a high definition television signal at 74.25 MHz is taken as an example. FIG. 2 shows the format of this video signal. There is a horizontal blanking period of 280 pixels in the scanning line direction, and a vertical blanking period of 44 lines between the first field and the second field of n frames in the vertical direction is the second field of n frames and n + 1 frames. There is also a vertical blanking period of 45 lines between the first field and the first field. The shaded area in FIG. 2 indicates the effective scanning period. FIG. 3 shows an output video format of the format conversion circuit. First field and second of n frames
The head N line (X1F in the drawing) of the vertical blanking period of 44 lines between fields is replaced by the head N line (A2F in the drawing) of the second field (A2 in the drawing) and the final N line (X1L in the drawing). Is the first field (A in the figure)
It is replaced by the last N lines of 1) (A1L in the figure). The second field of the n frame (A2 in the figure) and n + 1
The first N lines (Y1 in the figure) of the vertical blanking period of 45 lines between the first fields (B1 in the figure) of the frame
F) is replaced with the first N lines (B1F in the drawing) of the first field of the n + 1 frame (B1 in the drawing), and the last N line (Y1L in the drawing) is the end of the second field (A2 in the drawing) of the n frame. It is replaced by the N line (A2L in the figure). The first N pixels (B2F in the drawing) of 280 pixels in the horizontal blanking period (B in the drawing) are in the next line (effective scanning period:
The first N pixels of A1H2) in the figure are replaced with the last N pixels.
The pixel (B2L in the drawing) is replaced with the last N pixels of the previous line (A1H1 in the drawing). By performing the format conversion in which the horizontal and vertical blanking periods are replaced by the video signals in the effective scanning periods before and after the sub-band division filter, the video signals in the effective scanning periods before and after the blanking period are treated as temporally continuous signals. It can be processed by the circuit 3. In the sub-band division filter circuit 3 of FIG. 1, the input format-converted video signal is divided into two bands in the horizontal direction by the filters H-LPFs 8 and 9 and down-sampled. FIG. 4 shows the operation of the H-LPF filtering process at the boundary of the horizontal blanking period. A is the last pixel in the horizontal effective scanning period H1, and B is the first pixel in the next horizontal effective scanning period H2. When the center tap of the H-LPF is in A, the N tap is the position of the replaced N pixel, and H1 and H2 are consecutive without performing special control such as stopping the filtering process in the blanking period. It can be easily understood that filtering processing is possible as a signal. It can also be understood that the processing result for the pixel A is obtained at this point and no delay occurs. Similarly, when B has a center tap of H-LPF, it can be easily understood that the filtering process can be performed as a signal in which H1 and H2 are continuous.

After the horizontal band division and the downsampling by the horizontal downsampling circuits 10 and 12 are performed, the filters V-LPFs 12 and 14 and V-HP are used.
The F13 and F15 subdivide the band in the vertical direction into two, and down-sample to output the subband signals of the four horizontal and vertical divisions to the output terminals 4, 5, 6, and 7. Also in the vertical filtering process, the vertical blanking period is replaced with the signal of the effective scanning period before and after, similarly to the horizontal subband division filtering process described above, so that the filtering process is stopped in the blanking period. It is possible to perform the filtering process as a continuous signal with the signal in the effective scanning period separated by the vertical blanking period without performing a special control such as turning on. Figure 5
3 shows the subband signal format output to the output terminal 4. In the figure, since the horizontal and vertical directions are downsampled, the number of horizontal pixels and the number of vertical lines are each halved. Note that 960 pixels × 259 lines in FIG. 5 are the encoded data period transmitted in one field. After that, encoding suitable for each subband signal characteristic is performed and transmitted to the subband signal in the effective scanning period.

FIG. 6 shows an embodiment of a subband decoding device corresponding to FIG. As for the order of the filter, the maximum of the low pass filter (LPF) or the high pass filter (HPF) is 2N + 1.

The transmitted encoded data of each sub-band signal is decoded and each sub-band signal is output to the input terminals 8, 9, 10, 11 of the format conversion circuit 24. The signal format at the input terminals 8, 9, 10 and 11 is defined by the effective scanning period (horizontal pixel 96 per field).
0: vertical line 259) is the same as in FIG. 5, but the blanking period has an appropriate value. The format conversion circuit 24 converts the format of each subband signal and outputs it to the subband synthesis filter circuit 25. Figure 7
The output format of the format conversion circuit 25 is shown in FIG. The top N / 2 line of the vertical blanking period of 22 lines between the first field and the second field is the second line.
Replace with the first N / 2 line of the field, last N / 2
The line is replaced with the last N / 2 lines in the first field. The leading N / 2 line of the vertical blanking period of 22.5 lines between the second field and the first field is replaced with the leading N / 2 line of the first field of the next frame, and the final N / 2 line is the It is replaced by the last N / 2 lines of 2 fields. The leading N / 2 pixels of the horizontal blanking period 140 pixels are replaced with the leading N / 2 pixels of the next line, and the final N / 2 pixels are replaced with the final N / 2 pixels of the previous line. The number of lines and the number of pixels to be replaced here are halved on the transmitting side because the subband signals are downsampled in the horizontal and vertical directions, respectively. The format-converted subband signals are output to the subband synthesis filter circuit 25. In the subband synthesis filter circuit 25 of FIG. 6, first, vertical upsampling is performed in the vertical upsampling circuits 27, 28, 29, and 3.
0, and band synthesis in the vertical direction is performed by adders 35 and 36.
Then, horizontal upsampling is performed by the horizontal upsampling circuits 37 and 38.
These signals are passed through a horizontal subband synthesizing low-pass filter 39 and a horizontal direction subband synthesizing high-pass filter 40, respectively, and then added by an adder circuit 41 to perform horizontal band synthesizing and output terminal 26. The playback video signal is output to. Also in the filtering process of the receiving side sub-band synthesis filter circuit, the blanking period is replaced with the signal of the effective scanning period before and after as in the sub-band division filtering process described above, so that the filtering process is performed in the blanking period. It is possible to perform the filtering process as a continuous signal with the signals in the effective scanning period separated by the blanking period without performing special control such as stopping. Second embodiment of the present invention

In the first embodiment, format conversion is performed in which the signal in the blanking period is replaced so that the signal in the effective scanning period with the blanking period separated becomes a continuous signal. As a format conversion that achieves the same effect as that of the first embodiment, there is a format conversion in which the signal during the effective scanning period is symmetrically folded with the boundary point between the blanking period and the effective scanning period as the symmetry point. The frame format after this format conversion is shown in FIG. As an effect of this format conversion, in addition to the effect similar to that of the first embodiment, it can be mentioned that the coding efficiency after subband division is higher than that of the first embodiment. In the first embodiment, at the boundary point between the blanking period and the effective scanning period, the sub-band division processing is performed on the uncorrelated signals separated by the blanking period. Therefore, in the encoding circuit after the sub-band division. Although the coding efficiency is reduced, in the present embodiment, since the subband division processing is performed on the signal having a high correlation even at the boundary of the blanking period by folding back symmetrically, the encoding circuit after the subband division is performed. It is possible to perform encoding without lowering the encoding efficiency. In addition to this, this format is also effective for encoding a still image.

[0014]

As described above, according to the present invention, when a video signal having a blanking period is subjected to subband division / combination, format conversion is performed so that the subband is not taken into consideration. It becomes possible to operate the division / synthesis filter.

[Brief description of drawings]

FIG. 1 is a diagram of a subband division filter circuit including a format conversion circuit of the present invention.

FIG. 2 is a diagram showing an input video signal format.

FIG. 3 is a diagram showing an output format of a format conversion circuit in the first embodiment.

FIG. 4 is a diagram showing a signal format and a filtering operation at a boundary of a horizontal blanking period.

FIG. 5 is a diagram showing a signal format after subband division.

FIG. 6 is a diagram of a subband synthesis filter circuit including the format conversion circuit of the present invention.

FIG. 7 is a diagram showing an output format of a receiving side format conversion circuit.

FIG. 8 is a diagram showing a subband encoding / decoding device.

FIG. 9 is a diagram showing an output format of a format conversion circuit in the second embodiment.

[Explanation of symbols]

1, 20, 21, 22, 23 ... Input terminals 4, 5, 6, 7, 26 ... Output terminals 8 ... Horizontal subband splitting low-pass filter 9 ... Horizontal subband splitting high-pass filter 10, 11 ... Horizontal direction Down-sampling circuit 12, 14 ... Low-pass filter for vertical direction sub-band division 13, 15 ... High-pass filter for vertical direction sub-band division 16, 17, 18, 19 ... Vertical direction down-sampling circuit 27, 28, 29, 30 ... Vertical direction Up-sampling circuit 31, 33 ... Low-pass filter for vertical sub-band synthesis 32, 34 ... High-pass filter for vertical sub-band synthesis 35, 36, 41 ... Adder circuit 37, 38 ... Horizontal up-sampling circuit 39 ... Horizontal sub-band Low pass filter for synthesis 40 ... For horizontal sub-band synthesis Bypass filter

Claims (1)

[Claims] 1. A transmitting side divides a video signal having an effective scanning period and a blanking period into N sub-band signals, and then encodes each of the N sub-band signals to be encoded. The encoded data of the N sub-band signals is transmitted to the receiving side, and the receiving side decodes the encoded data of the transmitted N sub-band signals respectively to decode the N sub-band signals. In the sub-band coding / decoding device that synthesizes N sub-band signals after the conversion to video signals and transmits and reproduces the video signals, the transmitting side has a format in which the signal in the blanking period is replaced with the video signal in the effective scanning period. After conversion, N
Divide into sub-band signals and transmit only the coded data of the effective scanning period, the receiving side decodes the transmitted encoded data of the effective scanning period, and the data that is not transmitted in the blanking period is
Characteristic of transmitting and reproducing a video signal by performing format conversion to replace the decoded data in the transmitted effective scanning period, synthesizing N subband signals, and processing the blanking period after synthesizing And a subband encoding / decoding device.