Low bit-rate audio coding systems and methods that use expanding quantizers with arithmetic coding
First Claim
1. An audio encoding transmitter that receives an input signal representing an audio signal and generates an output signal conveying an encoded representation of the audio signal, the audio encoding transmitter comprising:
- an analysis filterbank that generates a plurality of subband signals representing frequency subbands of the audio signal in response to the input signal, wherein each subband signal comprises one or more subband-signal components;
a quantizer coupled to the analysis filterbank that generates one or more quantized subband signals by quantizing subband-signal components of one or more of the subband signals using a first quantizing accuracy for subband-signal component values within a first interval of values and using a second quantizing accuracy for subband-signal component values within a second interval of values, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval;
an encoder coupled to the quantizer that generates one or more encoded subband signals by encoding the one or more quantized subband signals using a lossless encoding process that reduces information capacity requirements of the quantized subband signals; and
a formatter coupled to the encoder that assembles the one or more encoded subband signals into the output signal.
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Abstract
The perceived quality of an audio signals obtained from very low bit-rate audio coding system is improved by using expanding quantizers and arithmetic coding in a transmitter and using complementary compression and arithmetic decoding in a receiver. An expanding quantizer is used to control the number of signal components that are quantized to zero and arithmetic coding is used to efficiently code the quantized-to-zero coefficients. This allows a wider bandwidth and more accurately quantized baseband signal to be conveyed to the receiver, which regenerates an output signal by synthesizing the missing components.
53 Citations
60 Claims
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1. An audio encoding transmitter that receives an input signal representing an audio signal and generates an output signal conveying an encoded representation of the audio signal, the audio encoding transmitter comprising:
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an analysis filterbank that generates a plurality of subband signals representing frequency subbands of the audio signal in response to the input signal, wherein each subband signal comprises one or more subband-signal components; a quantizer coupled to the analysis filterbank that generates one or more quantized subband signals by quantizing subband-signal components of one or more of the subband signals using a first quantizing accuracy for subband-signal component values within a first interval of values and using a second quantizing accuracy for subband-signal component values within a second interval of values, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval; an encoder coupled to the quantizer that generates one or more encoded subband signals by encoding the one or more quantized subband signals using a lossless encoding process that reduces information capacity requirements of the quantized subband signals; and a formatter coupled to the encoder that assembles the one or more encoded subband signals into the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An audio decoding receiver that receives an input signal conveying an encoded representation of an audio signal and generates an output signal representing the audio signal, the audio decoding receiver comprising:
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a deformatter that obtains one or more encoded subband signals from the input signal; a decoder coupled to the deformatter that generates one or more decoded subband signals by decoding the one or more encoded subband signals using a lossless decoding process that increases information capacity requirements of the encoded subband signals, wherein each decoded subband signal comprises one or more subband-signal components and represents a respective frequency subband of the audio signal; a dequantizer coupled to the decoder that generates one or more dequantized subband signals by dequantizing subband-signal components of the one or more decoded subband signals, wherein the dequantizer is complementary to a quantizer that uses a first quantizing accuracy for values within a first interval of values and uses a second quantizing accuracy for values within a second interval of values, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval; and a synthesis filterbank coupled to the dequantizer that generates the output signal in response to a plurality of subband signals including the one or more dequantized subband signals. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A medium that is readable by a device and that conveys a program of instructions executable by the device to perform an audio encoding method that comprises steps performing the acts of:
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applying an analysis filterbank to the input signal to generate a plurality of subband signals representing frequency subbands of the audio signal, wherein each subband signal comprises one or more subband-signal components; quantizing subband-signal components of one or more of the subband signals using a first quantizing accuracy for subband-signal component values within a first interval of values and using a second quantizing accuracy for subband-signal component values within a second interval of values to generate one or more quantized subband signals, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval; encoding the one or more quantized subband signals using a lossless encoding process that reduces information capacity requirements of the quantized subband signals to generate one or more encoded subband signals; and assembling the one or more encoded subband signals into the output signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A medium that is readable by a device and that conveys a program of instructions executable by the device to perform an audio decoding method that comprises steps performing the acts of:
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obtaining one or more encoded subband signals from the input signal; decoding the one or more encoded subband signals using a lossless decoding process that increases information capacity requirements of the encoded subband signals to generate one or more decoded subband signals, wherein each decoded subband signal comprises one or more subband-signal components and represents a respective frequency subband of the audio signal; dequantizing subband-signal components of the one or more decoded subband signals to generate one or more dequantized subband signals, wherein the dequantizing is complementary to quantizing that uses a first quantizing accuracy for values within a first interval of values and uses a second quantizing accuracy for values within a second interval of values, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval; and applying a synthesis filterbank to a plurality of subband signals including the one or more dequantized subband signals to generate the output signal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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33. An audio encoding transmitter that receives an input signal representing an audio signal and generates an output signal conveying an encoded representation of the audio signal, the audio encoding transmitter comprising:
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an analysis filterbank that generates a plurality of subband signals representing frequency subbands of the audio signal in response to the input signal, wherein each subband signal comprises one or more subband-signal components; a quantizer coupled to the analysis filterbank that quantizes one or more of the subband signals to generate quantized subband signals, wherein for a subband signal having one or more first subband-signal components and one or more second subband-signal components with magnitudes less than the one or more first subband-signal components, the second subband-signal components are pushed into a range of values that are quantized into fewer quantizing levels than would occur without pushing, thereby decreasing quantizing accuracy and reducing entropy of the quantized second subband-signal components; an encoder coupled to the quantizer that generates one or more encoded subband signals by encoding the one or more quantized subband signals using an entropy encoding process that reduces information capacity requirements of the quantized subband signals; and a formatter coupled to the encoder that assembles the one or more encoded subband signals into the output signal. - View Dependent Claims (34, 35, 36, 37, 38, 39)
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40. An audio decoding receiver that receives an input signal conveying an encoded representation of an audio signal and generates an output signal representing the audio signal, the audio decoding receiver comprising:
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a deformatter that obtains one or more encoded subband signals from the input signal; a decoder coupled to the deformatter that generates one or more decoded subband signals by decoding the one or more encoded subband signals using an entropy decoding process that increases information capacity requirements of the encoded subband signals, wherein each decoded subband signal comprises one or more subband-signal components and represents a respective frequency subband of the audio signal; a dequantizer coupled to the decoder that generates one or more dequantized subband signals by dequantizing subband-signal components of the one or more decoded subband signals, wherein the dequantizer is complementary to a quantizer that, for a subband signal having one or more first subband-signal components and one or more second subband-signal components with magnitudes less than the one or more first subband-signal components, pushes the second subband-signal components into a range of values to quantize them into fewer quantizing levels than would occur without pushing, thereby decreasing quantizing accuracy and reducing entropy of the quantized second subband-signal components; and a synthesis filterbank that generates the output signal in response to a plurality of subband signals including the one or more dequantized subband signals. - View Dependent Claims (41, 42, 43, 44, 45, 46)
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47. A medium that is readable by a device and that conveys a program of instructions executable by the device to perform an audio encoding method that comprises steps performing the acts of:
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applying an analysis filterbank to the input signal to generate a plurality of subband signals representing frequency subbands of the audio signal, wherein each subband signal comprises one or more subband-signal components; quantizing subband-signal components of one or more of the subband signals to generate quantized subband signals, wherein for a subband signal having one or more first subband-signal components and one or more second subband-signal components with magnitudes less than the one or more first subband-signal components, the second subband-signal components are pushed into a range of values that are quantized into fewer quantizing levels than would occur without pushing, thereby decreasing quantizing accuracy and reducing entropy of the quantized second subband-signal components; encoding the one or more quantized subband signals using an entropy encoding process that reduces information capacity requirements of the quantized subband signals to generate one or more encoded subband signals; and assembling the one or more encoded subband signals into the output signal. - View Dependent Claims (48, 49, 50, 51, 52, 53)
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54. A medium that is readable by a device and that conveys a program of instructions executable by the device to perform an audio decoding method that comprises steps performing the acts of:
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obtaining one or more encoded subband signals from the input signal; decoding the one or more encoded subband signals using a lossless decoding process that increases information capacity requirements of the encoded subband signals to generate one or more decoded subband signals, wherein each decoded subband signal comprises one or more subband-signal components and represents a respective frequency subband of the audio signal; dequantizing subband-signal components of the one or more decoded subband signals to generate one or more dequantized subband signals, wherein the dequantizing is complementary to quantizing that uses a first quantizing accuracy for values within a first interval of values and uses a second quantizing accuracy for values within a second interval of values, wherein the first quantizing accuracy is lower than the second quantizing accuracy, the first interval is adjacent to the second interval, and values within the first interval are smaller than values within the second interval; and applying a synthesis filterbank to a plurality of subband signals including the one or more dequantized subband signals to generate the output signal. - View Dependent Claims (55, 56, 57, 58, 59, 60)
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Specification