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/***************************** MPEG-4 AAC Decoder ***************************
(C) Copyright Fraunhofer IIS 2000-2008
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.
$Id$
Author(s): Robert Weidner (DSP Solutions)
Description: HCR Decoder: Bitstream reading
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.
*******************************************************************************/
#include "aacdec_hcr_bit.h"
/*---------------------------------------------------------------------------------------------
description: This function toggles the read direction.
-----------------------------------------------------------------------------------------------
input: current read direction
-----------------------------------------------------------------------------------------------
return: new read direction
-------------------------------------------------------------------------------------------- */
UCHAR ToggleReadDirection(UCHAR readDirection)
{
if ( readDirection == FROM_LEFT_TO_RIGHT ) {
return FROM_RIGHT_TO_LEFT;
}
else {
return FROM_LEFT_TO_RIGHT;
}
}
/*---------------------------------------------------------------------------------------------
description: This function returns a bit from the bitstream according to read direction.
It is called very often, therefore it makes sense to inline it (runtime).
-----------------------------------------------------------------------------------------------
input: - handle to FDK bitstream
- reference value marking start of bitfield
- pLeftStartOfSegment
- pRightStartOfSegment
- readDirection
-----------------------------------------------------------------------------------------------
return: - bit from bitstream
-------------------------------------------------------------------------------------------- */
UINT HcrGetABitFromBitstream(HANDLE_FDK_BITSTREAM bs,
USHORT *pLeftStartOfSegment,
USHORT *pRightStartOfSegment,
UCHAR readDirection)
{
UINT bit;
INT readBitOffset;
if (readDirection == FROM_LEFT_TO_RIGHT) {
readBitOffset = *pLeftStartOfSegment-FDKgetBitCnt(bs);
if( readBitOffset ) {
FDKpushBiDirectional(bs, readBitOffset);
}
bit = FDKreadBits(bs, 1);
*pLeftStartOfSegment += 1;
}
else {
readBitOffset = *pRightStartOfSegment-FDKgetBitCnt(bs);
if( readBitOffset ) {
FDKpushBiDirectional(bs, readBitOffset);
}
/* to be replaced with a brother function of FDKreadBits() */
bit = FDKreadBits(bs, 1);
FDKpushBack(bs, 2);
*pRightStartOfSegment -= 1;
}
#if ERROR_GENERATOR_BIT_STREAM_HCR
static int a;
if ((++a % MODULO_DIVISOR_HCR) == 0) {
bit = (bit == 0) ? 1 : 0;
}
#endif
return (bit);
}
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