Advanced quantizer
First Claim
1. A transform-based audio encoder configured to encode an audio signal into a bitstream;
- the encoder comprising hardware implementinga quantization unit configured to determine a plurality of quantization indices by quantizing a plurality of coefficients from a block of coefficients using a dithered quantizer;
wherein the plurality of coefficients is associated with a plurality of corresponding frequency bins;
wherein the block of coefficients is derived from the audio signal;
a dither generator configured to select one of M pre-determined dither realizations, and configured to generate a plurality of pseudo-random dither values for quantizing the plurality of coefficients, respectively, based on the selected dither realization;
wherein M is an integer greater than one; and
an entropy encoder configured to select a codebook from M pre-determined codebooks, and configured to entropy encode the plurality of quantization indices using the selected codebook;
wherein the M pre-determined codebooks are associated with the M pre-determined dither realizations, respectively;
wherein the M pre-determined codebooks have been trained using the M pre-determined dither realizations, respectively;
wherein the entropy encoder is configured to select the codebook associated with the dither realization selected by the dither generator; and
wherein the transform-based audio encoder is configured to insert coefficient data indicative of the entropy encoded quantization indices into the bitstream.
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Abstract
The present document relates an audio encoding and decoding system (referred to as an audio codec system). In particular, the present document relates to a transform-based audio codec system which is particularly well suited for voice encoding/decoding. A quantization unit configured to quantize a first coefficient of a block of coefficients is described. The block of coefficients comprises a plurality of coefficients for a plurality of corresponding frequency bins. The quantization unit is configured to provide a set of quantizers. The set of quantizers comprises a plurality of different quantizers associated with a plurality of different signal-to-noise ratios, referred to as SNR, respectively. The plurality of different quantizers includes a noise-filling quantizer; one or more dithered quantizers; and one or more un-dithered quantizers. The quantization unit is further configured to determine an SNR indication indicative of a SNR attributed to the first coefficient, and to select a first quantizer from the set of quantizers, based on the SNR indication. In addition, the quantization unit is configured to quantize the first coefficient using the first quantizer.
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Citations
8 Claims
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1. A transform-based audio encoder configured to encode an audio signal into a bitstream;
- the encoder comprising hardware implementing
a quantization unit configured to determine a plurality of quantization indices by quantizing a plurality of coefficients from a block of coefficients using a dithered quantizer;
wherein the plurality of coefficients is associated with a plurality of corresponding frequency bins;
wherein the block of coefficients is derived from the audio signal;a dither generator configured to select one of M pre-determined dither realizations, and configured to generate a plurality of pseudo-random dither values for quantizing the plurality of coefficients, respectively, based on the selected dither realization;
wherein M is an integer greater than one; andan entropy encoder configured to select a codebook from M pre-determined codebooks, and configured to entropy encode the plurality of quantization indices using the selected codebook;
wherein the M pre-determined codebooks are associated with the M pre-determined dither realizations, respectively;
wherein the M pre-determined codebooks have been trained using the M pre-determined dither realizations, respectively;
wherein the entropy encoder is configured to select the codebook associated with the dither realization selected by the dither generator; and
wherein the transform-based audio encoder is configured to insert coefficient data indicative of the entropy encoded quantization indices into the bitstream. - View Dependent Claims (2, 3)
- the encoder comprising hardware implementing
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4. A transform-based audio decoder configured to decode a bitstream to provide a reconstructed audio signal;
- the decoder comprising hardware implementing
a dither generator configured to select one of M pre-determined dither realizations, and configured to generate a plurality of dither values based on the selected dither realization;
wherein M is an integer greater than one;
wherein the plurality of dither values is used by an inverse quantization unit comprising a dithered quantizer configured to determine a corresponding plurality of quantized coefficients based on a corresponding plurality of quantization indices; andan entropy decoder configured to select a codebook from M pre-determined codebooks and configured to entropy decode coefficient data from the bitstream using the selected codebook, to provide the plurality of quantization indices;
wherein the M pre-determined codebooks are associated with the M pre-determined dither realizations, respectively;
wherein the M pre-determined codebooks have been trained using the M pre-determined dither realizations, respectively; and
wherein the entropy decoder is configured to select the codebook associated with the dither realization selected by the dither generator;
wherein the entropy decoder is configured to determine the reconstructed audio signal based on the plurality of quantized coefficients.
- the decoder comprising hardware implementing
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5. A method for encoding an audio signal into a bitstream;
- the method comprising
determining a plurality of quantization indices by quantizing a plurality of coefficients from a block of coefficients using a dithered quantizer;
wherein the plurality of coefficients is associated with a plurality of corresponding frequency bins;
wherein the block of coefficients is derived from the audio signal;selecting one of M pre-determined dither realizations; generating a plurality of dither values for quantizing the plurality of coefficients, based on the selected dither realization;
wherein M is an integer greater one;selecting a codebook from M pre-determined codebooks; entropy encoding the plurality of quantization indices using the selected codebook;
wherein the M pre-determined codebooks are associated with the M pre-determined dither realizations, respectively;
wherein the M pre-determined codebooks have been trained using the M pre-determined dither realizations, respectively;
wherein the selected codebook is associated with the selected dither realization; andinserting coefficient data indicative of the entropy encoded quantization indices into the bitstream.
- the method comprising
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6. A method for decoding a bitstream to provide a reconstructed audio signal;
- the method comprising
selecting one of M pre-determined dither realizations; generating a plurality of dither values based on the selected dither realization;
wherein M is an integer greater one;
wherein the plurality of dither values is used by an inverse quantization unit comprising a dithered quantizer to determine a corresponding plurality of quantized coefficients based on a corresponding plurality of quantization indices;selecting a codebook from M pre-determined codebooks; entropy decoding coefficient data from the bitstream using the selected codebook, to provide the plurality of quantization indices;
wherein the M pre-determined codebooks are associated with the M pre-determined dither realizations, respectively;
wherein the M pre-determined codebooks have been trained using the M pre-determined dither realizations, respectively; and
wherein the selected codebook is associated with the selected dither realization; anddetermining the reconstructed audio signal based on the plurality of quantized coefficients.
- the method comprising
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7. A method for encoding a speech signal into a bitstream;
- the method comprising;
receiving a plurality of sequential blocks of transform coefficients comprising a current block and one or more previous blocks;
wherein the plurality of sequential blocks is indicative of samples of the speech signal;determining a current block of flattened transform coefficients by flattening the corresponding current block of transform coefficients using a corresponding current block envelope; determining a current block of estimated flattened transform coefficients based on one or more previous blocks of reconstructed transform coefficients and based on one or more predictor parameters;
wherein the one or more previous blocks of reconstructed transform coefficients have been derived from the one or more previous blocks of transform coefficients;determining a current block of prediction error coefficients based on the current block of flattened transform coefficients and based on the current block of estimated flattened transform coefficients; and determining coefficient data for the bitstream based on quantization indices associated with the current block of prediction error coefficients; encoding the speech signal into the bitstream based on the coefficient data.
- the method comprising;
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8. A method for decoding a bitstream to provide a reconstructed speech signal;
- the method comprising
determining a current block of estimated flattened transform coefficients based on one or more previous blocks of reconstructed transform coefficients and based on one or more predictor parameters derived from the bitstream; determining a current block of quantized prediction error coefficients based on coefficient data comprised within the bitstream; determining a current block of reconstructed flattened transform coefficients based on the current block of estimated flattened transform coefficients and based on the current block of quantized prediction error coefficients; determining a current block of reconstructed transform coefficients by providing the current block of reconstructed flattened transform coefficients with a spectral shape, using a current block envelope; and determining the reconstructed speech signal based on the current block of reconstructed transform coefficients.
- the method comprising
Specification