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Audio entropy encoder/decoder for coding contexts with different frequency resolutions and transform lengths

  • US 8,930,202 B2
  • Filed: 01/11/2011
  • Issued: 01/06/2015
  • Est. Priority Date: 07/11/2008
  • Status: Active Grant
First Claim
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1. An audio encoding apparatus for encoding a sequence of segments of coefficients, the segments being subsequent to each other in time, the audio encoder comprising:

  • a provider configured to provide the sequence of segments of coefficients from an audio stream representing a sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions;

    a processor configured to derive a coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment, the previous and current segments corresponding to different frequency resolutions and different transform lengths, respectively; and

    an entropy encoder configured to entropy encode the current coefficient based on the coding context to acquire an encoded audio stream;

    wherein the entropy encoder is adapted for encoding the current coefficient in units of a tuple of spectral coefficients and for predicting a range of the tuple based on the coding context; and

    wherein the entropy encoder is adapted for dividing the tuple by a predetermined factor as often as necessitated to fit a result of the division in a predetermined range and for encoding a number of divisions necessitated, a division remainder and the result of the division when the tuple does not lie in the predicted range, and for encoding the tuple without the use of any division when the tuple already lies within the predicted range.

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