EP0746116A2
Expired / Lapsed
EP
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MPEG audio decoder
Assignee: Mitsubishi Electric Corp
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Filing: 1996-05-30
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Granted: —
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Expires: 2016-05-30
Abstract
Abstract An MPEG audio decoder has an irregular-pattern processing circuit for detecting irregular patterns in the bit stream input to the decoder, and altering these irregular patterns, or altering data or signals derived from these irregular patterns, so that the irregular patterns do not cause annoying defects in the audio signal output from the decoder. The alteration may take the form of replacement by a minimum value, or interpolation of a preceding value. <IMAGE>
Inventors
- 👤 Yukari c/o Mitsubishi Denki K.K. Hiratsuka
- 👤 Kazuhiro C/O Mitsubishi Denki K.K. Sugiyama
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 19:52
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/005; H; H04; H04B; H04B1/00; H04B1/66; H04B1/665
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
268 words
An MPEG audio decoder for decoding an input bit stream comprising a plurality of frames coded according to an MPEG audio coding method, comprising: a frame unpacking means (2) for unpacking header information, bit allocation information, scale-factor information, and sample data from each of said frames; a bit allocation decoding means (4) coupled to said frame unpacking means (2), for decoding said bit allocation information to obtain decoded bit allocation values; a scale-factor decoding means (5) coupled to said frame unpacking means (2), for decoding said scale-factor information to obtain decoded scale-factor values; an inverse quantizing means (6) coupled to said frame unpacking means (2), for dequantizing said sample data according to said decoded bit allocation information to obtain dequantized sample values; an inverse normalizing means (7) coupled to said inverse quantizing means (6), for denormalizing said dequantized sample values according to said decoded scale-factor values to obtain denormalized sample values; a subband audio signal synthesizing means (8) coupled to said inverse normalizing means (7), for synthesizing an output audio signal from said denormalized sample values; and an irregular-pattern processing means, coupled to at least one means among said frame unpacking means (2), said bit allocation decoding means (4), said scale-factor decoding means (5), said inverse quantizing means (6), said inverse normalizing means (7), and said subband audio signal synthesizing means (8), for detecting irregular patterns in said input bit stream and altering at least one corresponding entity among said decoded scale-factor values, said sample data, said dequantized sample values, and said output audio signal, thereby preventing said irregular patterns from causing defects in said output audio signal.
Claim 2
Dependent Claim
78 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: a '1111'-pattern detecting means (11) for detecting irregular patterns equal to '1111' in said bit allocation information, when said header information indicates that said input bit stream is encoded according to MPEG Layer One; and a muting means (13) for muting said output audio signal when an irregular pattern equal to '1111' is detected in said bit allocation information by said '1111'-pattern detecting means (11).
Claim 3
Dependent Claim
90 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: a '1111'-pattern detecting means (11) for detecting irregular patterns equal to '1111' in said bit allocation information, when said header information indicates that said input bit stream is encoded according to MPEG Layer One; and an interpolating means (15) for replacing one portion of said output audio signal with a preceding portion of said output audio signal, when an irregular pattern equal to '1111' is detected in said bit allocation information by said '1111'-pattern detecting means (11).
Claim 4
Dependent Claim
61 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: a '111111'-pattern detecting means (31) for detecting irregular patterns equal to '111111' in said scale-factor information; and a replacement means for replacing said irregular patterns equal to '111111' with scale-factor information equal to '111110,' which is decoded to a minimum scale-factor value by said scale-factor decoding means (5).
Claim 5
Dependent Claim
76 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: a '111111'-pattern detecting means (31) for detecting irregular patterns equal to '111111' in said scale-factor information; a zero-generator (35) for generating a scale-factor value equal to zero; and a switch (36) for replacing a scale-factor value output by said scale-factor decoding means (5) with said scale-factor value equal to zero, when said '111111'-pattern detecting means (31) detects an irregular pattern equal to '111111.'
Claim 6
Dependent Claim
84 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: a '111111'-pattern detecting means (31) for detecting irregular patterns equal to '111111' in said scale-factor information; a first memory (52) for temporarily storing said scale-factor information, when said '111111'-pattern detecting means (31) does not detect an irregular pattern equal to '111111;' and a replacement means (53) for replacing an irregular pattern equal to '111111' detected by said '111111'-pattern detecting means (31) with preceding scale-factor information stored in said first memory (52).
Claim 7
Dependent Claim
72 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: an 'all-1' detecting means (71) for detecting irregular 'all-1' patterns in the sample data received by said inverse quantizing means (6); and an MSB inverting means (72) for inverting a most significant bit of the irregular 'all-1' patterns detected by said 'all-1' detecting means, thereby converting said irregular 'all-1' patterns to patterns representing a dequantized sample value of zero.
Claim 8
Dependent Claim
89 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: an 'all-1' detecting means (71) for detecting irregular 'all-1' patterns in the sample data received by said inverse quantizing means (6); a memory (82) for temporarily storing the sample data received by said inverse quantizing means (6), when said 'all-1' detecting means (71) does not detect an irregular 'all-1' pattern; and a replacement means (83) for replacing the irregular 'all-1' patterns detected by said 'all-1' detecting means (71) with sample data stored in said memory (82).
Claim 9
Dependent Claim
132 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: an irregular sample-data-pattern detecting means (91) for detecting irregular patterns in the sample data received by said inverse quantizing means (6), said irregular patterns including an 'all-1' pattern and, when said header information and said bit allocation information designate MPEG Layer Two and a number of quantization steps equal to one of the integers three, five, and nine, at least one other pattern; and a minimum-value converting means (92) for converting all sample data values derived from the irregular patterns detected by said irregular sample-data-pattern detecting means (91) to sample data values representing dequantized sample values of zero, and furnishing said sample data values representing dequantized sample values of zero to said inverse quantizing means (6) to be dequantized.
Claim 10
Dependent Claim
160 words
The MPEG audio decoder of claim 1, wherein said irregular-pattern processing means comprises: an irregular sample-data-pattern detecting means (91) for detecting irregular patterns in the sample data received by said inverse quantizing means (6), said irregular patterns including an 'all-1' pattern and, when said header information and said bit allocation information designate MPEG Layer Two and a number of quantization steps equal to one of the integers three, five, and nine, at least one other irregular pattern; a second memory (94) for temporarily storing the sample data received by said inverse quantizing means (6), when said irregular sample-data-pattern detecting means (91) does not detect an irregular pattern; and a replacement means (96) for replacing all sample data values derived from the irregular patterns detected by said irregular sample-data-pattern detecting means (91) with sample data stored in said second memory (94), and furnishing said sample data stored in said second memory (94) to said inverse quantizing means (6) to be dequantized.
Claim 11
Independent Claim
140 words
A method of decoding an input bit stream coded according to an MPEG audio coding method by unpacking said input bit stream into header information, bit allocation information, scale-factor information, and sample data, dequantizing and denormalizing said sample data according to said bit allocation information and scale-factor information to obtain subband data representing subband components in successive frames, and synthesizing an output audio signal from said subband data, comprising the steps of: determining from said header information whether said input bit stream conforms to MPEG Layer One; detecting irregular patterns equal to '1111' in said bit allocation information, when said input bit stream conforms to MPEG Layer One; and altering said audio output signal, when an irregular pattern equal to '1111' is detected, thereby preventing said irregular pattern equal to '1111' from causing a defect in said output audio signal.
Claim 12
Dependent Claim
19 words
The method of claim 11, wherein said step of altering comprises muting said audio output signal for one frame.
Claim 13
Dependent Claim
33 words
The method of claim 11, wherein said step of altering comprises replacing the audio output signal for the frame affected by said irregular pattern with the audio output signal for a preceding frame.
Claim 14
Independent Claim
98 words
A method of decoding an input bit stream coded according to an MPEG audio coding method by unpacking said input bit stream into header information, bit allocation information, scale-factor information, and sample data, dequantizing and denormalizing said sample data according to said bit allocation information and scale-factor information to obtain subband data, and synthesizing an output audio signal from said subband data, comprising the steps of: detecting irregular patterns in said input bit stream; and replacing said irregular patterns with patterns that are not irregular, thereby preventing said irregular patterns from causing defects in said output audio signal.
Claim 15
Dependent Claim
24 words
The method of claim 14, wherein said step of replacing comprises replacing said irregular patterns with patterns received previously in said input bit stream.
Claim 16
Dependent Claim
31 words
The method of claim 14, wherein said step of replacing comprises replacing an irregular pattern of scale-factor information equal to '111111' with the pattern '111110' representing a scale factor of 0.00000120155435.
Claim 17
Dependent Claim
28 words
The method of claim 14, wherein said step of replacing comprises replacing an irregular pattern of sample data with a pattern representing a dequantized sample value of zero.
Claim 18
Dependent Claim
59 words
The method of claim 14, wherein said input bit stream conforms to MPEG Layer Two, comprising the further steps of: detecting irregular patterns representing granules of sample data; and when an irregular pattern representing a granule of sample data is thus detected, replacing all sample data in said granule with sample data representing a dequantized data value of zero.
Claim 19
Dependent Claim
65 words
The method of claim 14, wherein said input bit stream conforms to MPEG Layer Two, comprising the further steps of: storing said sample data in a memory (94); detecting irregular patterns representing granules of sample data; and when an irregular pattern representing a granule of sample data is thus detected, replacing all sample data in said granule with a single value selected from said memory.
Claim 20
Independent Claim
96 words
A method of decoding an input bit stream coded according to an MPEG audio coding method by unpacking said input bit stream into header information, bit allocation information, scale-factor information, and sample data, dequantizing and denormalizing said sample data according to said bit allocation information and scale-factor information to obtain subband data, and synthesizing an output audio signal from said subband data, comprising the steps of: decoding said scale-factor information to obtain a scale factor; detecting scale-factor information equal to '111111;' and replacing said scale-factor information equal to '111111' with a scale factor equal to zero.
Claim 21
Dependent Claim
99 words
An audio decoder for decoding an input bit stream, comprising a plurality of frames coded according to a digital audio coding method, to produce an output audio signal, each frame of the input bit stream having audio data coded to comprise a plurality of words, said audio decoder comprising means for individually checking each of said plurality of words to detect a specific bit pattern in a word, and means for altering said specific bit pattern, or a corresponding part of the output audio signal, to prevent said specific bit pattern from causing defects in said output audio signal.
Claim 22
Dependent Claim
24 words
An audio decoder according to claim 21, wherein said plurality of words are bit allocation data and/or scale factor data and/or encoded sample data.
References Cited (Backward Citations)
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