Data processing: speech signal processing – linguistics – language – Audio signal bandwidth compression or expansion
Patent
1996-06-21
1998-06-09
Hudspeth, David R.
Data processing: speech signal processing, linguistics, language
Audio signal bandwidth compression or expansion
704230, 704220, G01L 9100
Patent
active
057651361
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an encoded data decoding apparatus and an image audio multiplexed data decoding apparatus using the same and, more particularly, to an encoded data decoding apparatus suitable for expanding audio data which is compressed for transmission or recording to a recording medium in order to reproduce and an image audio multiplexed data decoding apparatus using the same.
BACKGROUND ART
Hitherto, there are various methods for high efficient encoding (data compression) a signal such as audio signal, voice, or the like. One of them is, for example, a band division encoding method (sub-band encoding method) in which the audio signal or the like is divided into a plurality of frequency bands and encoded. As an example of the sub-band encoding method, there is a method of ISO/IEC 11172-3 as an international standardization called an MPEG audio method.
Although an encoding apparatus according to the sub-band encoding method is well known as disclosed in, for example, Japanese Patent Application Nos. 6-204449 and 6-204450 (corresponding U.S. patent application Ser. No. 08/511449), such an apparatus will now be described with reference to FIG. 10 for better understanding the invention.
In FIG. 10, for a digital audio signal supplied to an input terminal 50, an audio signal is sampled at a predetermined time interval by a dividing filter bank circuit 30 to obtain the audio signal included in the time interval (called one frame). Signal components of different frequencies included in the audio signal of each frame are divided into a plurality of predetermined frequency bands and floating processes are applied to the signals of the divided frequency bands by floating processing circuits 31, 32, 33, and 34, respectively.
In this instance, the floating process is a process for multiplying a common value to the signal component in each of the divided bands, thereby increasing its value in order to raise the precision of a quantizing process by a subsequent quantizing circuit. For example, a maximum value among the absolute values of the signal components included in the respective bands is searched and the floating process is carried out by using a floating coefficient which is determined to increase the maximum value to a value as large as possible, but not saturated, namely, not exceeding "1". In Table 1, examples of the floating coefficients to be used in the foregoing method of ISO/IEC 11172-3 are shown.
TABLE 1 ______________________________________
Floating Floating
Index Coefficient Index Coefficient
______________________________________
0 2.00000000000000
31 0.00155019633981
1 1.58740105196820
32 0.00123039165029
2 1.25992104989487
33 0.00097656250000
3 1.00000000000000
34 0.00077509816991
4 0.79370052598410
35 0.00061519582514
5 0.62996052494744
36 0.00048828125000
6 0.50000000000000
37 0.00038754908495
7 0.39685026299205
38 0.00030759791257
8 0.31498026247372
39 0.00024414062500
9 0.25000000000000
40 0.00019377454248
10 0.19842513149602
41 0.00015379895629
11 0.15748013123686
42 0.00012207031250
12 0.12500000000000
43 0.00009688727124
13 0.09921256574801
44 0.00007689947814
14 0.07874506561843
45 0.00006103515625
15 0.06250000000000
46 0.00004844363562
16 0.04960628287401
47 0.00003844973907
17 0.03937253280921
48 0.00003051757813
18 0.03125000000000
49 0.00002422181781
19 0.02480314143700
50 0.00001922486954
20 0.01966626640461
51 0.00001525878906
21 0.01562500000000
52 0.00001211090890
22 0.01240157071850
53 0.00000961243477
23 0.00984313320230
54 0.00000762939453
24 0.00781250000000
55 0.00000605545445
25 0.00620078535925
56 0.00000480621738
26 0.00492156660115
57 0.00000381469727
27 0.00390625000000
58 0.00000302772723
28 0.00310039267963
59 0.00000240310869
29 0.00246078330058
60 0.00000190734863
30 0.00185312500000
61 0.00000151386361
62 0.00000120155435
______________________________________
In the encoding apparatus in FIG. 10, th
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Hudspeth David R.
Nippon Steel Corporation
Wieland Susan
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