Coding of sparse digital media spectral data
First Claim
1. A method of compressively encoding audio signal data containing a time series of audio signal samples as a compressed data stream, the method comprising:
- transforming successive blocks of the audio signal data into sets of spectral coefficients;
quantizing the spectral coefficients;
for at least a portion of the spectral coefficients in the sets, detecting any spectral peaks out of the spectral coefficients in the portion;
correlating spectral peaks detected out of the set of spectral coefficients for a current block to spectral peaks detected out of the spectral coefficients for a preceding block of the audio signal data; and
encoding information to represent those of the spectral peaks for the current block that correlate to spectral peaks for the preceding block in the compressed data stream using temporal prediction coding and encoding information to represent at least some of the spectral peaks in the compressed data stream using at least one three value combination of a length of a run of zero-valued spectral coefficients and levels of two spectral coefficients following the run.
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Accused Products
Abstract
An audio encoder/decoder provides efficient compression of spectral transform coefficient data characterized by sparse spectral peaks. The audio encoder/decoder applies a temporal prediction of the frequency position of spectral peaks. The spectral peaks in the transform coefficients that are predicted from those in a preceding transform coding block are encoded as a shift in frequency position from the previous transform coding block and two non-zero coefficient levels. The prediction may avoid coding very large zero-level transform coefficient runs as compared to conventional run length coding. For spectral peaks not predicted from those in a preceding transform coding block, the spectral peaks are encoded as a value trio of a length of a run of zero-level spectral transform coefficients, and two non-zero coefficient levels.
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Citations
17 Claims
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1. A method of compressively encoding audio signal data containing a time series of audio signal samples as a compressed data stream, the method comprising:
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transforming successive blocks of the audio signal data into sets of spectral coefficients; quantizing the spectral coefficients; for at least a portion of the spectral coefficients in the sets, detecting any spectral peaks out of the spectral coefficients in the portion; correlating spectral peaks detected out of the set of spectral coefficients for a current block to spectral peaks detected out of the spectral coefficients for a preceding block of the audio signal data; and encoding information to represent those of the spectral peaks for the current block that correlate to spectral peaks for the preceding block in the compressed data stream using temporal prediction coding and encoding information to represent at least some of the spectral peaks in the compressed data stream using at least one three value combination of a length of a run of zero-valued spectral coefficients and levels of two spectral coefficients following the run. - View Dependent Claims (2, 3, 4, 5)
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6. An audio data processor, comprising:
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an input for receiving an audio data stream containing a time series of audio signal samples; a time-frequency transform for transforming successive blocks of the audio signal samples to produce sets of spectral coefficients; a spectral peak encoder operating to detect spectral peaks in at least a portion of the spectral coefficient sets, and operating to encode individual ones of the detected spectral peaks using one of a temporal prediction coding and a zero run coding, wherein the spectral peak encoder operates to correlate the detected spectral peaks in the portion of successive spectral coefficient sets to those in the portion of their preceding spectral coefficient sets, and to encode the detected spectral peaks that correlate to spectral peaks in preceding spectral coefficient sets using the temporal prediction coding and otherwise to encode the detected spectral peaks using the zero run coding. - View Dependent Claims (7, 8, 9, 10, 16)
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11. A computer-readable data storage device having instructions carried thereon, the instructions being executable by an audio data processor to perform a method of compressing an audio data stream, the method comprising:
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transforming successive blocks of a time sample audio data stream into sets of spectral coefficients; quantizing the spectral coefficients; encoding the spectral coefficients into a compressed audio data stream, wherein said encoding for at least a portion of the spectral coefficients of a set comprises; identifying spectral peaks among the spectral coefficients of the portion; correlating the identified spectral peaks of the set to spectral peak of a preceding set; encoding those of the identified spectral peaks of the set that correlate to spectral peaks of the preceding set using a temporal prediction coding; and encoding those of the identified spectral peaks of the set that lack correlation to spectral peaks of the preceding set using a zero run length coding. - View Dependent Claims (12, 13, 14, 15)
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17. A method of decoding, comprising:
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receiving a compressed audio data stream produced by the method including; transforming successive blocks of the audio signal data into sets of spectral coefficients; quantizing the spectral coefficients; for at least a portion of the spectral coefficients in the sets, detecting any spectral peaks out of the spectral coefficients in the portion; correlating spectral peaks detected out of the set of spectral coefficients for a current block to spectral peaks detected out of the spectral coefficients for a preceding block of the audio signal data; and encoding information to represent those of the spectral peaks for the current block that correlate to spectral peaks for the preceding block in the compressed data stream using temporal prediction coding and encoding information to represent at least some of the spectral peaks in the compressed data stream using at least one three value combination of a length of a run of zero-valued spectral coefficients and levels of two spectral coefficients following the run; reading information representing spectral peaks from the compressed data stream; for the spectral peak information encoded using at least one three value combination, decoding the three value combination code to determine spectral coefficients for the spectral peak from the values of zero-run length and levels; for the spectral peak information encoded using temporal prediction coding, decoding the combination code to determine spectral coefficients for the spectral peak from the value of the shift and the peak coefficient levels; de-quantizing the spectral coefficients; and inverse transforming the spectral coefficients to reconstruct the time series of audio signal samples.
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Specification