Lossless audio coder
AssigneeDigital Voice Systems, Inc.
InventorJohn C. Hardwick
Life of this patent
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Abstract
A lossless coding method may be used to compress information, such as audio data, without introducing any artifacts. This lossless coding method may be used to compress audio signals for use in storage and/or transmission of audio data. The audio data may be compressed by first dividing digital samples taken from the audio data into frames. A predictor is then used on the frames to generate prediction coefficients that can then be quantized to form predictor bits. The frames may then be subdivided into subsets. Another predictor can be used on the subsets to produce error samples that can be entropy coded into codeword bits. The predictor bits and codeword bits can be included in the compressed audio output for use in decoding.
Claims60
A method of compressing digital samples obtained from an audio signal into output bits, the method comprising:
- dividing the digital samples into one or more frames, each frame including multiple digital samples;
- computing a first predictor for the digital samples in a frame, wherein the first predictor is characterized by first prediction coefficients;
- quantizing the first prediction coefficients to produce first predictor bits;
- dividing the digital samples in a frame into one or more subsets, each subset containing at least one of the digital samples in the frame;
- computing a subset predictor for at least one of the subsets, wherein the subset predictor is computed using digital samples contained in previous subsets;
- processing the digital samples for the at least one of the subsets using both the first predictor bits and the subset predictor to produce error samples;
- entropy coding the error samples to produce codewords bits;
- and
- including the first predictor bits and the codeword bits in the output bits.
A method of compressing digital samples obtained from an audio source into output bits, the method comprising:
- dividing the digital samples into frames, each frame including at least one of the digital samples;
- processing the digital samples to produce error samples;
- entropy coding the error samples to produce codewords bits, wherein the entropy coding is characterized by at least a first code parameter and a second code parameter, the first code parameter and the second code parameter being variable from frame to frame;
- and
- including the codeword bits in the output bits.
A device configured to compress digital samples obtained from an audio signal into output bits, the device comprising:
- an input unit configured to receive digital samples obtained from an audio signal;
- and
- a processor connected to the input unit to receive the digital samples, the processor being configured to:
- divide the digital samples into one or more frames, each frame including multiple digital samples;
- compute a first predictor for the digital samples in a frame, the first predictor being characterized by first prediction coefficients;
- quantize the first prediction coefficients to produce first predictor bits;
- divide the digital samples in a frame into one or more subsets, with each subset containing at least one of the digital samples in the frame;
- compute a subset predictor for at least one of the subsets using digital samples contained in previous subsets;
- process the digital samples for the at least one of the subsets using both the first predictor bits and the subset predictor to produce error samples;
- entropy code the error samples to produce codewords bits;
- and
- produce output bits including the first predictor bits and the codeword bits.
A device configured to compress digital samples obtained from an audio source into output bits, the device comprising:
- an input unit configured to receive digital samples obtained from an audio signal;
- and
- a processor connected to the input unit to receive the digital samples, the processor being configured to:
- divide the digital samples into frames, each frame including at least one of the digital samples;
- process the digital samples to produce error samples;
- entropy code the error samples to produce codewords bits, the entropy coding being characterized by at least a first code parameter and a second code parameter, the first code parameter and the second code parameter being variable from frame to frame;
- and
- produce output bits including the codeword bits.
A method of reconstructing audio data from output bits generated by an audio coder, the method comprising:
- receiving the output bits generated by the audio coder;
- obtaining codeword bits, a first code parameter, a second code parameter, and predictor bits from the output bits;
- reconstructing error samples from the codeword bits using the first code parameter and the second code parameter;
- reconstructing prediction coefficients using the predictor bits, wherein the predictor bits were previously generated by quantizing the prediction coefficients;
- and
- reconstructing audio data using the prediction coefficients and the error samples.
A method of reconstructing audio samples, the audio samples divided into one or more frames and encoded by an audio coder, the method comprising:
- obtaining codeword bits from an input stream, the input stream including side information;
- obtaining side information from the input stream, and reconstructing first prediction coefficients using the side information;
- reconstructing error samples for a frame from the codeword bits;
- dividing the error samples for a frame into one or more subsets, each subset containing at least one of the error samples for the frame;
- computing a subset predictor for at least one of the subsets, wherein the subset predictor is computed using information from previous subsets;
- and
- reconstructing audio samples using the first prediction coefficients, the subset predictor and the error samples.
Dependencies are inferred from the claim text.