libSBRdec/src/sbr_scale.h

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  83
  84 /*!
  85 \file
  86 \brief Sbr scaling factors,
  87 To deal with the dynamic range in the different processing stages, a
  88 fixed point specific code has to rely on scaling factors. A floating
  89 point code carries a scaling factor -- the exponent -- for each value,
  90 so scaling is not necessary there.
  91
  92 The output of the core decoder (low band) is scaled up to cover as much
  93 as possible bits for each value. As high band and low band are processed
  94 in different algorithm sections, they require their own scaling
  95 factors. In addition, any static buffers, e.g. filter states, require a
  96 separate scaling factor as well. The code takes care to do the proper
  97 adjustment, if scaling factors of a filter state and the time signal differ.
  98
  99 \sa #QMF_SCALE_FACTOR, \ref documentationOverview
 100 */
 101
 102 #ifndef __SBR_SCALE_H
 103 #define __SBR_SCALE_H
 104
 105 /*!
 106 \verbatim
 107   scale:
 108     0             left aligned e.g. |max| >=0.5
 109     FRACT_BITS-1  zero e.g |max| = 0
 110 \endverbatim
 111
 112   Dynamic scaling is used to achieve sufficient accuracy even when the signal
 113   energy is low.  The dynamic framing of SBR produces a variable overlap area
 114   where samples from the previous QMF-Analysis are stored. Depending on the
 115   start position and stop position of the current SBR envelopes, the processing
 116   buffer consists of differently scaled regions like illustrated in the below
 117   figure.
 118
 119   \image html scales.png Scale
 120 */
 121
 122
 123 #endif