JPH06164409A - Band division encoding method - Google Patents

Abstract

PURPOSE:To maintain a high quality signal with respect to audiovisual characteristics by providing a means which gives a priority level to each band in a limited intra-buffer capacity and determining the code volume of each band by this priority level to adjust the bit generation volume due to encoding between bands. CONSTITUTION:The audio signal inputted from a signal input terminal 101 is divided into four bands S1 to S4 in the order from the lowest frequency band by a band dividing circuit 102. When the band S1 has 5.5M-bit intra-buffer capacity, the quantization width is limited to the range of '4' to '13', and it is not changed because it is within the range. A multiplexer 108 performs this discrimination to send '9', '11', and '14' as the quantization width to first, second, and fourth encoding circuits 103, 104, and 106 respectively and sends the same '8' as before a prescribed time interval to a third encoding circuit 105. If a condition that the quantization width of bands other than the band S is not smaller than that of the band S1 is imposed, the multiplexer sends '9' to the third encoding circuit 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band division coding method for dividing a signal such as an image signal, an audio signal or the like into a plurality of frequency bands by a band division circuit for coding.

[0002]

2. Description of the Related Art Subband coding is known as one of high-efficiency coding techniques for image signals, audio signals and the like. A conventional example of the band division encoding device when an audio signal is input will be described below.

FIG. 4 is a block diagram showing an example of a band division coding apparatus for realizing a conventional band division coding method. In FIG. 4, 401 is a signal input terminal, 402 is a band dividing circuit, 403 is a first encoding circuit, 404 is a second encoding circuit, 40
5 is a third encoding circuit, 406 is a fourth encoding circuit, 407 is a multiplexer circuit, and 408 is a signal output terminal. The operation will be described below with reference to FIG.

The audio signal input from the signal input terminal 401 is divided into four bands by the band dividing circuit 402. The four divided signals are input to the first coding circuit 403, the second coding circuit 404, the third coding circuit 405, and the fourth coding circuit 406, respectively, and coded by each coding circuit. . At the time of encoding, bit allocation is previously allocated to each encoding circuit so as to match a predetermined transfer rate. A first encoding circuit 403, a second encoding circuit 404, a third encoding circuit 405,
The signal encoded by the fourth encoding circuit 406 is multiplexed by the multiplexer circuit 407 and output to the signal output terminal 408 (see, for example, "Digital Co.," written by NS Jayant-Peter Noll.
ding of Waveform "pp486-509).

[0005]

However, in the above-mentioned configuration, the bit allocation to each band is unique, the coding is not performed according to the property of the input signal which changes from moment to moment, and the band is divided. There is a problem that high quality coding cannot be performed because it does not correspond to a change in signal information.

[0006]

In order to solve the above-mentioned problems, a band-division coding method of the present invention monitors a buffer for controlling a transfer rate and a buffer internal capacity at a predetermined time interval t. And a means for prioritizing each band by using the coding distortion amount of each band observed at the interval t, and a code amount control for determining the code amount of each band from the priority by a predetermined method. The coding amount is controlled by sending a signal for each band.

[0007]

According to the present invention, by the method described above, there is provided means for prioritizing each band within the limited buffer capacity, and the coding amount is determined by determining the code amount of each band based on the priority. The bit generation amount can be adjusted between bands, and a high-quality signal can be held in terms of audiovisual characteristics.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The band division coding method of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a band division coding apparatus for realizing the band division coding method of the present invention. In FIG. 1, 101 is a signal input terminal, 102 is a band division circuit, 103 is a first encoding circuit, 104 is a second encoding circuit, 105 is a third encoding circuit, 106 is a fourth encoding circuit, 107.
Is a coding amount control circuit, 108 is a multiplexer circuit, and 109 is a signal output terminal. The operation of the coding method of the band division coding apparatus configured as described above will be described below with reference to FIG.

The audio signal input from the signal input terminal 101 is divided by the band dividing circuit 102 into _four bands of S ₁ , S ₂ , S ₃ and S ₄ from the low frequency band. The divided four band signals are coded as follows. The first encoding circuit 103 performs DCT encoding on the S ₁ band signal. The second encoding circuit 104 uses DP for the S ₂ band signal.
CM coding is performed. The third encoding circuit 105 performs PCM encoding on the S ₃ band signal. The fourth encoding circuit 106,
PCM encoding is performed on the S ₄ band signal. The multiplexer circuit 108 multiplexes the signals encoded by the first encoding circuit 103, the second encoding circuit 104, the third encoding circuit 105, and the fourth encoding circuit 106, and outputs the multiplexed signal to the signal output terminal 109. .

The code output from the coding amount control circuit 107 will be described below.
An example in which the signal control signal has a quantization width is shown below.
Ming is not limited to this, variable length table
If you can control the amount of coding, such as a signal that changes
I don't know. The coding amount control circuit 107 includes a first coding circuit 103,
Second encoding circuit 104, third encoding circuit 105, fourth encoding circuit
Receives from path 106 the amount of coding distortion that has occurred during time interval t.
It Now suppose they D₁, D₂, D₃, D_FourAnd
S₁, S₂, S₃, S_FourK in advance for the four bands₁, K₂, K
₃, K_FourHas a weighting coefficient of
Circuit 107 is D₁× K ₁, D₂× K₂, D₃× K₃, D_Four× K_Four
Is calculated, and the priority is given in the order of the largest distortion. That conclusion
Fruit, S₂, S₁, S_Four, S₃It is assumed that the order of the bands is. Change
The coding amount control circuit 107
The buffer capacity changed during the interval t
Take from road 108. Now suppose that capacity is 5.5M each
bit and +11000 bit. Also, the code amount before the time interval t
The control signal, here the quantization width, is the first code
8 for the encoding circuit 103, 10 for the second encoding circuit 104, and 3 for the third encoding circuit.
The encoding circuit 105 was 8 and the fourth encoding circuit 106 was 13.
To do.

FIG. 2 shows the buffer capacity and the buffer change amount.
FIG. 7 is a diagram showing increase / decrease in quantization width for each priority order according to FIG. Figure
From 2, the buffer capacity is 5.5 Mbit, the change amount is + 11000bit
If so, the three highest priority bands can change the quantization width.
And S₂, S₁, S_Four3 bands are selected, each
Increase the quantization width by 1. Figure 3 shows the buffer capacity
Against S₁Black out the range of quantization width that the band of
FIG. From this FIG. 3, S₁The bandwidth of
If the buffer capacity is 5.5 Mbit, the quantization width is 4 to 13
You can see that it is limited to the range, but it is within the range
Therefore, it is not changed. The above judgment is performed
The plexer circuit 108 outputs the quantization width to the first encoding circuit 103 by 9
To the second encoding circuit 104 and 14 to the fourth encoding circuit 106.
Is sent, and the same 8 as before t is sent to the third encoding circuit 105.
To do. However, S₁Bands other than S ₁Below the quantization width of the band
If the condition is not satisfied, S₃of
The quantization width of the band becomes 9 and is quantized by the third encoding circuit 105.
Send a width of 9.

In this embodiment, the input signal is an audio signal, the number of band divisions is 4, and the coding method of the coding circuit is DCT, DPCM, PCM, but the present invention is limited to these. Not what is done,
Other signals, number of bands, and encoding method may be used.
Further, by setting the quantization width to 1 to 16, the priority is determined as shown in FIG. 2 and the code amount control signal for the capacity in the buffer is limited as shown in FIG. 3, but it is limited to this. Not a thing. Furthermore, the method of determining the priority order and the method of determining the coding amount control signal from the priority order are not limited to this.

[0014]

As described above, according to the present invention, there is provided means for prioritizing each band within the limited buffer capacity, and the code amount of each band is determined by the priority. The amount of bits generated by encoding can be adjusted between bands, and a high-quality signal can be held in terms of audiovisual characteristics.

Further, by limiting the code amount control signal with respect to the capacity in the buffer, the code amount can be controlled without causing overflow or underflow of the buffer.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a band division encoding apparatus according to an embodiment of a band division encoding method of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a band division encoding method of the present invention.

FIG. 3 is an explanatory diagram showing an embodiment of a band division encoding method of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional band division encoding device of a band division encoding method.

[Explanation of symbols]

 102 band division circuit 103 first encoding circuit 104 second encoding circuit 105 third encoding circuit 106 fourth encoding circuit 107 encoding amount control circuit 108 multiplexer circuit

Claims (4)

[Claims] 1. A band division encoding method for dividing an input signal into a plurality of frequency bands for encoding, and a buffer for controlling a transfer rate and a capacity in the buffer at a predetermined time interval t. Means for prioritizing each band by using the coding distortion amount of each band observed at the interval t, and monitoring the priority, the buffer capacity, and the change amount of the buffer capacity. A band division coding method, wherein the coding amount is controlled by transmitting a code amount control signal for determining the code amount of each band by a predetermined method for each band. 2. A coding weighting amount of each band is multiplied by a predetermined weighting coefficient to give a priority order in descending order, and the high priority order is specified from the current buffer capacity and the buffer content change amount at the interval t. 2. The band division encoding method according to claim 1, wherein the code amount control signal different from the code amount control signal transmitted by the specific band before the time interval t is transmitted. 3. The band division encoding method according to claim 2, wherein the range that the code amount control signal can take is specified within a certain range by the capacity in the current buffer. 4. The code amount control signal is given by a quantization width, and the quantization width received by a band other than the lowest frequency band is not less than a quantization width received by the lowest frequency band. Item 4. The band division encoding method according to Item 3.