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diff --git a/src/libfaad/sbr_dec.c b/src/libfaad/sbr_dec.c
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+++ b/src/libfaad/sbr_dec.c
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+/*
+** FAAD - Freeware Advanced Audio Decoder
+** Copyright (C) 2002 M. Bakker
+**  
+** This program is free software; you can redistribute it and/or modify
+** it under the terms of the GNU General Public License as published by
+** the Free Software Foundation; either version 2 of the License, or
+** (at your option) any later version.
+** 
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+** GNU General Public License for more details.
+** 
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software 
+** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+**
+** $Id: sbr_dec.c,v 1.1 2002/07/14 23:43:01 miguelfreitas Exp $
+**/
+
+/*
+   SBR Decoder overview:
+
+   To achieve a synchronized output signal, the following steps have to be
+   acknowledged in the decoder:
+    - The bitstream parser divides the bitstream into two parts; the AAC
+      core coder part and the SBR part.
+    - The SBR bitstream part is fed to the bitstream de-multiplexer followed
+      by de-quantization The raw data is Huffman decoded.
+    - The AAC bitstream part is fed to the AAC core decoder, where the
+      bitstream data of the current frame is decoded, yielding a time domain
+      audio signal block of 1024 samples. The block length could easily be
+      adapted to other sizes e.g. 960.
+    - The core coder audio block is fed to the analysis QMF bank using a
+      delay of 1312 samples.
+    - The analysis QMF bank performs the filtering of the delayed core coder
+      audio signal. The output from the filtering is stored in the matrix
+      Xlow. The output from the analysis QMF bank is delayed tHFGen subband
+      samples, before being fed to the synthesis QMF bank. To achieve
+      synchronization tHFGen = 32, i.e. the value must equal the number of
+      subband samples corresponding to one frame.
+    - The HF generator calculates XHigh given the matrix XLow. The process
+      is guided by the SBR data contained in the current frame.
+    - The envelope adjuster calculates the matrix Y given the matrix XHigh
+      and the SBR envelope data, extracted from the SBR bitstream. To
+      achieve synchronization, tHFAdj has to be set to tHFAdj = 0, i.e. the
+      envelope adjuster operates on data delayed tHFGen subband samples.
+    - The synthesis QMF bank operates on the delayed output from the analysis
+      QMF bank and the output from the envelope adjuster.
+ */
+
+#include "common.h"
+
+#ifdef SBR
+
+#include "sbr_syntax.h"
+#include "sbr_qmf.h"
+
+#endif