JP2800520B2 - Shift calculation circuit and moving picture coding apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to audio signal and image signal processing, and more particularly to a moving picture coding system.

[0002]

2. Description of the Related Art In various kinds of signal processing, there is a method of performing processing by dividing a one-dimensional signal or a two-dimensional signal into frequency bands. It is used for compression coding of audio signals and image signals. For this technique, for example, a sub-band (subb
and) the division scheme is based on NS Giant and Peter Nor (N.S. Jayant and Pete)
r Pollis Hall, Inc. (PR
ENTICE-HALL Inc, USA), 198 C.E.
"Digital Coding of Waveform"("Digital Coding of Waveform")
Waveforms ") in Chapter 11.

[0003] This technique is briefly illustrated in FIG. The input signal is input to a plurality of band-pass filters H1, H2, H3, H4 of the sub-band dividing circuit 60. These filters have different pass band characteristics. After the filter, appropriate thinning is performed in the thinning circuits 21, 22, 23, and 24, and adjustment is performed so that the number of samples of the input signal is equal to the number of processed samples. In the simplest example, N
If one filter is used, N: 1 decimation is performed after each filter. The above is the sub-band division method. A method of synthesizing these divided signals is also shown in FIG. Each divided signal is interpolated by the zero signal in the interpolators 31, 32, 33, and 34 of the sub-band synthesis circuit 70, converted into a signal having the same sample rate as the original signal, and then filtered by the filters G1, G2, G3, and G4. Are added to each other in the addition circuit 50.

Several filters have been proposed to guarantee that a signal is completely reconstructed even after these divisions and synthesis. For example, a quadrature filter has been proposed.
reMirror Filter (hereinafter abbreviated as QMF), Conjugated Q
A uadature filter (hereinafter abbreviated as CQF) and a wavelet filter have been proposed. QM
F is described in detail in "Digital Coding of Waveform", and CQF is described in, for example, M. J. T. Smith and T. P. Barnwell (MJT Smith and TP.
Barnwell), "Exact Reconstruction for Tree Structured Subband Coders", IEE, Transactions on Acoustic Speech and Signal Processing, June 1986, Vol. 34, p. 434 (Exact reconstruction)
Tion for tree-structured
Subband coders, "IWEEE Tra
ns. on Acoustic. , Speech and
Signal Processing, Vol. A
SSP-34, pp, 434-441, June 198
6. In detail, regarding the wavelet filter, for example, Ingrid Debussy "Orthonormal Basis of Compactly Supported Wavelets" Communication on Pure and &
Applied Massmatics, 1988 AD, 4th
1, pages 909-996 (I. Daubechie)
s, "Orthonormal Bases of C
Ompactly Supported Wavelet
s, "Commun. on Pure and Ap
Plied Mathematics, Vol. XL
I, 909-996, 1988. ).

[0005]

However, since the sample rate in each frequency band is thinned out compared to the original signal, it may be difficult to easily operate the original signal. For example, consider an example in which each of the above frequency bands is thinned out to N: 1. In this case, the operation is simple because N sample shifts on the original signal correspond to one sample shift on each frequency band. However, 1 on the original signal
The calculation of the sample shift over the frequency band is not always clear.

However, once the divided signals are synthesized,
A method of performing a shift operation and dividing again into subbands is possible. However, this operation involves the operation of subband division and synthesis, and is expensive in terms of circuitry.

It is an object of the present invention to clearly define the shift calculations on the divided frequency bands.

Another object of the present invention is to establish a shift calculation on a frequency band which does not include the operation of combining and dividing subbands.

It is still another object of the present invention to provide a motion-compensated inter-frame predictive coding method on a frequency-divided signal.

[0010]

According to a first aspect of the present invention, there is provided a circuit for performing a sample position shift calculation on a signal decomposed into a plurality of frequency bands. Means for applying a filter obtained by synthesizing a synthesis filter corresponding to the band, a decomposition filter for a shift amount and a frequency band to be subjected to position shift operation, and means for adding the results of those filter calculations, For a signal decomposed into a plurality of frequency bands that realizes a position shift calculation with an accuracy higher than the resolution determined at the sample point in the frequency band, for each frequency band signal,
The shift calculation is realized by applying different filters and adding the results of the filter calculations.

According to the configuration of the second invention, the shift calculation is performed for all frequency bands.

According to the configuration of the third aspect of the present invention, among the N × N filters used in the configuration of the second aspect of the present invention, a filter having a small impulse response power is not calculated.

According to the configuration of the fourth invention, the original signal is divided into regions, the shift amount is defined for each region, and the shift calculation realized by the configuration of the first, second, and third inventions is performed for each region. Switching is performed according to the defined shift amount.

According to the fifth aspect of the present invention, means for dividing a two-dimensional signal of each frame into a frequency band for a moving image signal, and a difference between the frequency band-divided signal and a prediction signal described later. Means for calculating and obtaining a prediction error signal; means for quantizing the prediction error signal; means for encoding the quantized prediction error signal; and adding the quantized prediction error signal and the prediction signal. Means for obtaining a locally decoded signal by means of the above, means for delaying the locally decoded signal by one frame, means for dividing each frame of the moving image signal into regions and obtaining a motion vector for each region, By providing a means for performing the position shift calculation of the fourth invention as the shift amount on the locally decoded signal delayed by one frame and generating a prediction signal, motion compensation on the frequency-divided signal is provided. Realizing predictive coding between frames.

[0015]

As shown in FIG. 7, the interpolation circuits 31, 32, 33, and 34 of the subband synthesis circuit 70 perform interpolation with a zero signal to obtain a signal having the same sample rate as the original signal. , G4, and the sum is returned by the adder circuit 50 to restore the original signal representation. Then, the shift operation is performed in the shift circuit 80, and the plurality of band-pass filters H1, H1
2, H3, H4 and after filtering, thinning circuit 2
The operation in the case where subband division is performed by performing appropriate thinning in steps 1, 22, 23, and 24 is formulated. First, subband synthesis, shift, and subband division

[0016]

(Equation 1)

Can be expressed as Where b _l (n)
Is a signal of each frequency band, g _l (n) is a filter for the l-th band used for subband synthesis, x (n) is a synthesized signal, y (n) is a shifted signal thereof, and r is a shifted signal. The quantity h _l (n) is the filter for the l-th band used for subband division, and b _l ′ (n) is the signal of each shifted frequency band. By combining these three equations,

[0018]

(Equation 2)

From this equation, it can be seen that the shift calculation on the frequency band can be realized by performing a filter calculation on the signal of each frequency band and adding them. This has shown the validity of the configuration of the first invention.

In this configuration, the shift calculation is applied to only one frequency band, but it can be applied to all frequency bands. This is the configuration of the second invention.

In the configuration of the second invention, as shown in FIG. 2, N types of filters are applied to the N-divided signals, so that a total of N × N types of filters are required. That is, it is considered that a correction term is added from another frequency band in addition to the filter calculation in the frequency band.

If the frequency band is ideally divided, such correction terms can in principle be eliminated. However, a filter that realizes ideal frequency band division is impossible with a finite tap filter, and a finite length filter must be used, and such a correction term is required. It is conceivable that such a correction term has a significant value in adjacent frequency bands, but has almost a small value between distant frequency bands. Therefore, in the third invention, N ×
Instead of using all of the N types of filters, a filter calculation for generating such a correction term with a small contribution is not performed.

Further, in the fourth invention, the signal is divided into regions,
The shift amount is switched for each area.

The fifth invention is a configuration example applied to a moving picture coding system. As shown in FIG. 5, the input signal is divided into sub-bands in a sub-band dividing circuit 60, and a subtracter 202 calculates a difference from the prediction signal 300,
Then, the data is quantized by 02 and encoded. The quantized signal is
The original signal is restored by the inverse quantizer 204, the prediction signal 300 is added by the adder 205, and the frame delay unit 206
, And is subjected to motion compensation prediction by the shift calculation circuit 200 to become a prediction signal 300. This motion compensation portion is a shift calculation using a motion vector for each sub-block region separately obtained by the motion amount detector 207, and the above-described shift amount is switched for each region. The calculation method is applied.

[0025]

FIG. 1 shows a shift calculation circuit according to the configuration of the first invention. This shift calculation circuit applies filters F11, F21, F, which apply different filters to each frequency band signal, for a signal divided into a plurality of frequency bands.
31 and F41, and an adder 151 for adding the results of the filter calculations. The shift calculation of the first frequency band is performed by filtering and adding the signals of all the first to fourth frequency bands. With this circuit, position shift calculation with an accuracy higher than the resolution determined at the sample point in the frequency band can be realized.

FIG. 2 shows a shift calculation circuit according to the configuration of the second invention. This shift calculation circuit has a signal processing circuit for realizing position shift calculation within a frequency band for all frequency bands for a signal decomposed into a plurality of frequency bands. The signal processing circuit includes filters F11, F21,
F31, F41 and an adder 151 for adding the results of the filter calculations, and filters F12, F22, F3 for applying different filters to the respective frequency band signals.
2, F42 and an adder 152 for adding the results of the filter calculations, and filters F13, F23, F33, F for applying different filters to the respective frequency band signals.
43 and an adder 153 for adding the results of the filter calculations, and filters F14, F24, F34 and F44 for applying different filters to the respective frequency band signals, and an adder 154 for adding the results of the filter calculations. doing. According to this shift calculation circuit,
The shift calculation is performed not only on the first frequency band but also on signals in all frequency bands.

FIG. 3 shows a shift calculation circuit according to the configuration of the third invention. This shift calculation circuit includes a filter F1
1, F21 and an adder 151 for adding the results of the filter calculations, and filters F12, F22, and F3.
2 and an adder 152 that adds the results of the filter calculations, and filters F23, F33, and F43 and an adder 15 that adds the results of the filter calculations.
3 and filters F34 and F44 and an adder 154 for adding the results of the filter calculations. Compared to the configuration of the shift calculation circuit of FIG. 2, the filters from the first frequency band to the third and fourth frequency bands, the filters from the second frequency band to the fourth frequency band, and the third The filters from the frequency band to the first frequency band and the filters from the fourth frequency band to the first and second frequency bands are omitted.

FIG. 4 shows a shift calculation circuit according to the configuration of the fourth invention. The shift calculating circuit supplies a signal representing a shift amount to the filters in addition to the configuration shown in FIG. 3, and each filter switches the characteristics according to the shift amount.

FIG. 5 shows a moving picture coding apparatus using a shift calculation circuit according to the configuration of the fifth invention. This moving picture coding apparatus calculates a difference between a prediction signal and a subband dividing circuit 60 for dividing a two-dimensional signal of each frame into a frequency band with respect to a moving picture signal. , A quantizer 203 for quantizing the prediction error signal, an inverse quantizer 204 for encoding the quantized prediction error signal, and a quantizer for the quantized prediction error signal and the prediction signal. An adder 205 that additionally obtains a locally decoded signal; a frame delay unit 206 that delays the locally decoded signal by one frame; and a motion amount that divides each frame of the moving image signal into regions and obtains a motion vector for each region A detector 207 performs a position shift calculation of the fourth invention on the locally decoded signal delayed by one frame using the motion vector as a position shift amount to generate a prediction signal. And a preparative calculation circuit 200.

In this moving picture coding apparatus, an input signal is divided by a sub-band dividing circuit 60 and a subtracting circuit 202
The difference from the prediction signal 300 is calculated by the
Is quantized and encoded. The quantized signal is restored by the inverse quantizer 204, added with the prediction signal by the adder 205, delayed by one frame by the frame delay unit 206, and subjected to motion compensation prediction by the shift calculation circuit 200. A prediction signal 300 is obtained. This motion compensation part is a shift calculation using a motion vector for each sub-block region separately obtained by the motion amount detector 207, and the above-described shift calculation is performed after frequency band division in which the shift amount is switched for each region. The method is applied.

[0031]

According to the shift calculation circuit of the present invention, shift calculation can be realized while being divided into frequency bands. In particular, it becomes possible to generate a motion-compensated prediction signal in the frequency domain in the moving picture coding apparatus.

[Brief description of the drawings]

FIG. 1 shows a shift calculation circuit according to the configuration of the first invention.

FIG. 2 is a shift calculation circuit according to the configuration of the second invention.

FIG. 3 is a shift calculation circuit according to the configuration of the third invention.

FIG. 4 shows a shift calculation circuit according to the configuration of the fourth invention.

FIG. 5 is a moving picture coding apparatus using a shift calculation circuit according to the configuration of the fifth invention.

FIG. 6 is a diagram illustrating subband division and synthesis.

FIG. 7 is a diagram illustrating subband synthesis, shift, and subband division.

[Explanation of symbols]

21, 22, 23, 23 4: 1 thinning circuit 31, 32, 33, 33 1: 4 interpolation (interpolates zero signal) circuit 60 subband division circuit 70 subband synthesis circuit 80 shift circuit 151, 152, 153 154 Adder 202 Subtractor 203 Quantizer 204 Dequantizer 205 Adder 206 Frame delay 207 Motion detector H Bandpass filter used for subband division G Bandpass filter used for subband synthesis F Shift calculation Filter used to do

Claims (5)

(57) [Claims] 1. A circuit for performing a sample position shift calculation on a signal decomposed into a plurality of frequency bands, comprising:
For a wavenumber band, a synthesis filter corresponding to that band
Shift amount and position shift
The filter obtained by synthesizing the decomposition filter
And a means for adding the results of the filter calculations, and realizes a position shift calculation with an accuracy higher than the resolution determined by the sample points in the frequency band. 2. A shift circuit comprising a signal processing circuit for realizing the intra-frequency-band position shift calculation according to claim 1, for a signal decomposed into a plurality of frequency bands. Calculation circuit. 3. The method according to claim 1, wherein when calculating the position shift in the frequency band, the impulse response power is small.
A shift calculation circuit, wherein a filter calculation of a filter is omitted. 4. A means for performing a position shift calculation according to claim 1, 2 or 3 for a one-dimensional or two-dimensional signal which is divided into regions and the amount of position shift is defined for each region. A one-dimensional or two-dimensional shift calculating circuit having means for adaptively switching the position shift calculation for each of the regions. 5. A means for frequency-band dividing a two-dimensional signal of each frame with respect to a moving picture signal, and means for calculating a difference between the frequency-band-divided signal and a prediction signal described later to obtain a prediction error signal. Means for quantizing the prediction error signal, means for encoding the quantized prediction error signal, and means for obtaining a locally decoded signal by adding the quantized prediction error signal and the prediction signal. 5. The position according to claim 4, wherein the local decoding signal is delayed by one frame, each frame of the moving image signal is divided into regions, and a motion vector is obtained for each region, and the motion vector is used as a position shift amount. Means for performing a shift calculation on the locally decoded signal delayed by one frame to generate a prediction signal.