From 9bf37cc9712506b2483650c82d3c41152337ef7e Mon Sep 17 00:00:00 2001 From: Dave Burke Date: Tue, 17 Apr 2012 09:51:45 -0700 Subject: Fraunhofer AAC codec. License boilerplate update to follow. Change-Id: I2810460c11a58b6d148d84673cc031f3685e79b5 --- libSBRdec/src/sbr_scale.h | 65 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 libSBRdec/src/sbr_scale.h (limited to 'libSBRdec/src/sbr_scale.h') diff --git a/libSBRdec/src/sbr_scale.h b/libSBRdec/src/sbr_scale.h new file mode 100644 index 0000000..b1614cb --- /dev/null +++ b/libSBRdec/src/sbr_scale.h @@ -0,0 +1,65 @@ +/**************************************************************************** + + (C) Copyright Fraunhofer IIS (2005) + All Rights Reserved + + Please be advised that this software and/or program delivery is + Confidential Information of Fraunhofer and subject to and covered by the + + Fraunhofer IIS Software Evaluation Agreement + between Google Inc. and Fraunhofer + effective and in full force since March 1, 2012. + + You may use this software and/or program only under the terms and + conditions described in the above mentioned Fraunhofer IIS Software + Evaluation Agreement. Any other and/or further use requires a separate agreement. + + + This software and/or program is protected by copyright law and international + treaties. Any reproduction or distribution of this software and/or program, + or any portion of it, may result in severe civil and criminal penalties, and + will be prosecuted to the maximum extent possible under law. + + $Id$ + +*******************************************************************************/ +/*! +\file +\brief Sbr scaling factors, $Revision: 36841 $ +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 -- cgit v1.2.3