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Audio encoder/decoder with switching between first and second encoders/decoders using first and second framing rules

  • US 8,892,449 B2
  • Filed: 01/11/2011
  • Issued: 11/18/2014
  • Est. Priority Date: 07/11/2008
  • Status: Active Grant
First Claim
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1. An audio encoding apparatus for encoding audio samples, comprising:

  • a first time domain aliasing introducing encoder for encoding audio samples in a first encoding domain, the first time domain aliasing introducing encoder comprising a first framing rule, a start window and a stop window and comprising a frequency domain transformer for transforming a first frame of subsequent audio samples to the frequency domain based on a modified discrete cosine transformation (MDCT);

    a second encoder for encoding samples in a second encoding domain, the second encoder comprising a predetermined frame size number of audio samples, and a coding warm-up period number of audio samples, the second encoder comprising a different second framing rule, a frame of the second encoder being an encoded representation of a number of timely subsequent audio samples, the number being equal to the predetermined frame size number of audio samples; and

    a controller for, using a processor, switching from the first encoder to the second encoder or vice versa in response to a characteristic of the audio samples, and for modifying the start window or the stop window of the first encoder to the extent that a zero part thereof extends across a first quarter of an MDCT size and cross fade starts in a second quarter of the MDCT size so that the cross fade begins after a MDCT folding axis relative to the zero part, wherein the second framing rule remains unmodified.

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