JP3538931B2 - Signal expansion apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a compact disc (CD) and a digital audio tape (DA).
The present invention relates to a signal decompression device and method capable of outputting the word length of digital audio data recorded on a recording medium such as T) as data decompressed from original data.

[0002]

2. Description of the Related Art At present, recording media such as CDs and DATs include:
Data is recorded in a 16-bit recording format. In addition, professional recorders, AD converters and D
In the A converter, data is processed in 20 bits. For example, when converting digital audio data recorded by a recorder of 16 bits or more into a CD, data of 16 bits or less is simply discarded, or data of 16 bits or less is used by super bit mapping (SBM) or the like. A method of compressing to bits is used.

[0003]

By the way, there is no method for generating data of more than 16 bits from 16-bit data. For example, many digital mixers and DA converters can process data of 20 bits or 24 bits. Even if data whose word length has been truncated or compressed data is supplied to such a device, processing can be performed only with that word length. Further, even if the data is simply quantized using an A / D converter according to the theoretical value, the data cannot be processed with a resolution greater than the word length of the A / D converter.

Accordingly, it is an object of the present invention to provide a signal decompression apparatus and method capable of outputting data having a word length longer than the word length of original data.

[0005]

According to the present invention, a sampling point in the middle of an N-bit data sampling point is provided.
First interpolating means for interpolating N-bit data using M bits longer than N bits to generate L-bit data longer than N bits and shorter than M bits;
At the sampling point of N-bit data, the first complement
Interpolation using L-bit data generated by the interpolating means
This is a signal decompression device including second interpolation means for generating L-bit data .

Further, the present invention provides a method for supporting N-bit data .
At the sampling point in the middle of the sampling point,
N-bit data longer than N bit <br/> interpolation to using longer M bits than N bits, and generates data shorter L bits than M bits, the sampling point data of N bits, is generated This is a signal decompression method for generating L-bit data by interpolating using L-bit data .

[0007]

After the N-bit data X (n) is interpolated with M bits longer than the word length of the data X (n) in the interpolation filter 12, L-bit data having a word length shorter than M bits is obtained from the interpolated data. Generate Y (n). Data Y
(N) is supplied to the interpolation filter 13. The interpolation filter 13 uses the data Y (n) to generate the data X (n).
Are interpolated at the sampling point, and L-bit data Z (n) is output. In this way, data having a word length longer than the original data can be output.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a signal expansion apparatus according to the present invention. FIG. 1 is a block diagram of a signal decompression device according to the present invention. In FIG. 1, a predetermined format (for example,
Digital audio data modulated in AES / EBU format or IEC958 format)
The signal is demodulated by the decoder 2. Then, the data is supplied to the data decompression circuit 3. In the data expansion circuit 3, the word length of the supplied digital audio data is expanded based on the word length. The expanded digital audio data is supplied to the encoder 4. The encoder 4 modulates the digital audio data into a format of digital audio data before being supplied to the decoder 2. Encoder 4
Thus, the digital audio data expanded from the data input from the input terminal 1 is output to the output terminal 5.

FIG. 2 is a detailed block diagram of the data decompression circuit 3. The data expansion circuit 3 includes two interpolation filters 12 and 13 of the same type. As the interpolation filter, for example, an FIR filter can be used.
The decoded output X (n) of the decoder 2 is supplied to the interpolation filter 12 via the input terminal 11. Data X
(N) is data sampled at 1 / SF (sampling frequency) and quantized with N bits. From the interpolation filter 12, for the interpolation filter 13,
Data Y (n) is output. Data Y (n) is data interpolated based on data X (n). From the interpolation filter 13, the data Z is output to the output terminal 14.
(N) is output. Data Z (n) is data Y
This is data interpolated based on (n). Output terminal 1
The digital audio data output from 4 is supplied to the encoder 4.

FIG. 3 shows the data X (n) and Y (n) described above.
And Z (n). When the intermediate point of each data is interpolated using data of several points before and after based on each digital audio data (black circle) shown in FIG. 3A, data Y (n) (white circle) shown in FIG. 3B is obtained. Can be. Data Y (n) is the original data X (n)
Is generated by interpolating using M bits (N << M) that are sufficiently longer than the word length, and then rounding (N <L <M) or truncating to L bits. The word length of M bits at this time is set to such a length that an error can be ignored when calculating L-bit data.

The data Y (n) shown in FIG. 3B has, for example, four previous data and 3
It can be obtained by performing Lagrange interpolation using the subsequent data. The generation formula of this 7th-order Lagrange interpolation is

Y (n) = k0 × X (n−4) + k1 × X
(N−3) + k2 × X (n−2) + k3 × X (n−1)
+ K4 × X (n) + k5 × X (n + 1) + k6 × X (n
+2) + k7 × X (n + 3)

## EQU1 ## However,

K0 = -c1 * c2 * c3 * c4 * c5 *
c6 × c7 / 35 k1 = c0 × c2 × c3 × c4 × c5 × c6 × c7 × 4
/ 15 k2 = -c0xc1xc3xc4xc5xc6xc7x
6/5 k3 = c0 * c1 * c2 * c4 * c5 * c6 * c7 * 4 k4 = c0 * c1 * c2 * c3 * c5 * c6 * c7 * 4 k5 = -c0 * c1 * c2 * c3 * c4 * c6xc7x
6/5 k6 = c0 × c1 × c2 × c3 × c4 × c5 × c7 × 4
/ 15 k7 = -c0xc1xc2xc3xc4xc5xc6 /
35

Also,

C0 = (3 + 0.5) / 4 c1 = (2 + 0.5) / 3 c2 = (1 + 0.5) / 2 c3 = 0.5 c4 = 1-0.5 c5 = 1-0.5 / 2 c6 = 1-0.5 / 3 c7 = 1-0.5 / 4

It is assumed that

Next, when the data at the intermediate point of the data Y (n) is interpolated under the same conditions as described above, FIG.
Can be obtained. In addition,
An intermediate point of data Y (n), that is, data Z (n)
Coincides with the sampling point of the original data X (n). By performing such interpolation, it is possible to output N-bit input data (X (n)) as L-bit data having an expanded word length.

FIG. 4 is a diagram showing input data and output data of the signal decompression device according to the present invention. The X-axis is time and the Y-axis is amplitude level. The waveform shown in FIG. 4A is input data, and the waveform shown in FIG. 4B is output data. It is also assumed that 16-bit digital audio data is input as input data X (n), interpolated into 24- bit data Y (n), and then output as 24-bit data Z (n).

As can be seen from FIG. 4, the waveform of the 16-bit input data before interpolation has a stepped shape due to coarse quantization. On the other hand, the waveform of the 24-bit output data after interpolation is a waveform closer to an analog signal.

In the above description, Lagrange interpolation is used for the filter. However, the present invention can be realized by using, for example, linear interpolation or average value interpolation.

[0022]

According to the present invention, the word length of input data can be extended and output as a more analog signal, so that the S / N ratio of output data can be improved. Therefore, the sound quality of the output data can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a signal decompression device according to the present invention.

FIG. 2 is a detailed block diagram of a data decompression circuit.

FIG. 3 is a waveform diagram of input data and output data to an interpolation circuit.

FIG. 4 is a waveform diagram of input data and output data for the signal decompression device.

[Explanation of symbols]

3 Data expansion circuit 12, 13 interpolation filter

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03H 17/00-17/08 H03M 3/00-11/00 G11B 20/10-20/16 351

Claims (3)

(57) [Claims] 1. A sampling point for N-bit data .
At the sampling point in the middle of the
Longer than the N bits over data by interpolation using longer M bits than the N bits, and a first interpolation means for generating data of shorter L bits than the M bits, sampling points of data of said N-bit And above
A signal decompression device comprising: a second interpolation unit that generates L-bit data by interpolating using the L-bit data generated by the first interpolation unit. 2. The signal decompression device according to claim 1, wherein said N-bit data is digital audio data. 3. A sampling point for N-bit data .
At the sampling point in the middle of the
Longer than the N bits over data by interpolation using longer M bits than the N bits, and generates data shorter L bits than the M bits at a sampling point data of the N bits, the
L bi interpolated using the generated the L-bit data
A signal decompression method that generates data of a bit.