sbr_scale.h - Android社区 - https://www.androidos.net.cn/

/* -----------------------------------------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

1.    INTRODUCTION
The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
This FDK AAC Codec software is intended to be used on a wide variety of Android devices.

AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient general perceptual
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of the MPEG specifications.

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Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
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5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------------------------------------- */

/*!
\file
\brief Sbr scaling factors,  
To deal with the dynamic range in the different processing stages, a
fixed point specific code has to rely on scaling factors. A floating
point code carries a scaling factor -- the exponent -- for each value,
so scaling is not necessary there.

The output of the core decoder (low band) is scaled up to cover as much
as possible bits for each value. As high band and low band are processed
in different algorithm sections, they require their own scaling
factors. In addition, any static buffers, e.g. filter states, require a
separate scaling factor as well. The code takes care to do the proper
adjustment, if scaling factors of a filter state and the time signal differ.

\sa #QMF_SCALE_FACTOR, \ref documentationOverview
*/

#ifndef __SBR_SCALE_H
#define __SBR_SCALE_H

/*!
\verbatim
  scale:
    0             left aligned e.g. |max| >=0.5
    FRACT_BITS-1  zero e.g |max| = 0
\endverbatim

Dynamic scaling is used to achieve sufficient accuracy even when the signal
  energy is low.  The dynamic framing of SBR produces a variable overlap area
  where samples from the previous QMF-Analysis are stored. Depending on the
  start position and stop position of the current SBR envelopes, the processing
  buffer consists of differently scaled regions like illustrated in the below
  figure.

\image html scales.png Scale
*/

#endif

C++程序 | 124行 | 5.91 KB

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