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/* ------------------------------------------------------------------
* Copyright (C) 1998-2009 PacketVideo
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied.
* See the License for the specific language governing permissions
* and limitations under the License.
* -------------------------------------------------------------------
*/
/*
Pathname: getmask.c
------------------------------------------------------------------------------
REVISION HISTORY
Description: Modified from original shareware code
Description: Modified to pass variables by reference to eliminate use
of global variables.
Replaced for-loop style memory initialization with memset()
Description: (1) Modified to bring code in-line with PV standard
(2) Removed multiple returns, Replaced multiple 'if's with
switch
Description: (1) Modified per review comments
(2) increment pointer pMask after memset
Description: Make the maximum number of bits requested from getbits
become a constant.
Description: Typecast 1 to UInt32 for bitmask to avoid masking on a 16-bit
platform
Description: Replace some instances of getbits to get9_n_lessbits
when the number of bits read is 9 or less.
Who: Date: MM/DD/YYYY
Description:
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
pFrameInfo = pointer to structure that holds information for current
frame, Type FrameInfo
pInputStream= pointer to structure that holds input stream information
Type BITS
pGroup = pointer to array that holds the stop window index for
each group in current frame, Type Int
max_sfb = number of active sfbs for each window, Type Int
mask[] = array that holds the MS_mask information
Type Int
Local Stores/Buffers/Pointers Needed:
None
Global Stores/Buffers/Pointers Needed:
None
Outputs:
mask_present = 0 (no Mid/Side mixed)
2 (Mid/Side mixed present for entire frame)
1 (Mid/Side mixed information read from bitstream)
-1 (invalid mask_present read from bitstream)
Pointers and Buffers Modified:
pMask contents replaced by MS information of each scalefactor band
Local Stores Modified:
None
Global Stores Modified:
None
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
This function reads the Mid/Side(MS) mask information from the input
bitstream. If the mask_present field is equal to 2, the mask bits is set to
1 for the entire frame. If mask_present has a value of 0, the function
returns 0, If mask_present is set to 1, the Mid/Side(MS) information is
read from the input stream. When mask_present is 3, an error code (-1) is
generated.
The Mid/Side(MS) information is later used for mixing the left and right
channel sounds. Each scalefactor band has its own MS information.
(ISO comments: read a synthesis mask, read a synthesis mask uses
EXTENDED_MS_MASK and grouped mask )
------------------------------------------------------------------------------
REQUIREMENTS
This function shall replace the contents of pMask with the MS information
of each scalefactor band
------------------------------------------------------------------------------
REFERENCES
(1) MPEG-2 NBC Audio Decoder
"This software module was originally developed by AT&T, Dolby
Laboratories, Fraunhofer Gesellschaft IIS in the course of development
of the MPEG-2 NBC/MPEG-4 Audio standard ISO/IEC 13818-7, 14496-1,2 and
3. This software module is an implementation of a part of one or more
MPEG-2 NBC/MPEG-4 Audio tools as specified by the MPEG-2 NBC/MPEG-4
Audio standard. ISO/IEC gives users of the MPEG-2 NBC/MPEG-4 Audio
standards free license to this software module or modifications thereof
for use in hardware or software products claiming conformance to the
MPEG-2 NBC/MPEG-4 Audio standards. Those intending to use this software
module in hardware or software products are advised that this use may
infringe existing patents. The original developer of this software
module and his/her company, the subsequent editors and their companies,
and ISO/IEC have no liability for use of this software module or
modifications thereof in an implementation. Copyright is not released
for non MPEG-2 NBC/MPEG-4 Audio conforming products.The original
developer retains full right to use the code for his/her own purpose,
assign or donate the code to a third party and to inhibit third party
from using the code for non MPEG-2 NBC/MPEG-4 Audio conforming products.
This copyright notice must be included in all copies or derivative
works."
Copyright(c)1996.
(2) ISO/IEC 14496-3: 1999(E)
Subpart 4
p15 (Table 4.4.5 getmask)
------------------------------------------------------------------------------
PSEUDO-CODE
CALL getbits(LEN_MASK_PRES, pInputStream)
MODIFYING (pInputStream)
RETURNING (mask present information)
mask_present = mask present information
SWITCH (mask_present)
CASE (0):
BREAK;
CASE (2):
nwin = pFrameInfo->num_win;
FOR(win = 0; win < nwin; win = *(pGroup++))
FOR(sfb = pFrameInfo->sfb_per_win[win]; sfb > 0; sfb--)
*(pMask++) = 1;
ENDFOR
ENDFOR
BREAK;
CASE(1):
nwin = pFrameInfo->num_win;
nToDo = max_sfb;
WHILE (nToDo > 0)
nCall = nToDo;
IF (nCall > MAX_GETBITS)
THEN
nCall = MAX_GETBITS;
ENDIF
tempMask =
getbits(
nCall,
pInputStream);
bitmask = 1 << (nCall - 1);
FOR (sfb = nCall; sfb > 0; sfb--)
*(pMask++) = (tempMask & bitmask) >> (sfb - 1);
bitmask >>= 1;
ENDFOR
nToDo -= nCall;
END WHILE
pv_memset(
pMask,
0,
(pFrameInfo->sfb_per_win[win]-max_sfb)*sizeof(*pMask));
ENDFOR (win)
BREAK
DEFAULT:
mask_present = -1
ENDSWITCH
RETURN mask_present
------------------------------------------------------------------------------
*/
/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "pv_audio_type_defs.h"
#include "huffman.h"
#include "aac_mem_funcs.h"
#include "e_maskstatus.h"
/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL FUNCTION REFERENCES
; Declare functions defined elsewhere and referenced in this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/
Int getmask(
FrameInfo *pFrameInfo,
BITS *pInputStream,
Int group[],
Int max_sfb,
Int mask[])
{
Int win; /* window index */
Int sfb;
Int mask_present;
Int *pMask;
Int *pGroup;
Int nwin;
Int nCall;
Int nToDo;
UInt32 tempMask;
UInt32 bitmask;
pMask = mask;
pGroup = group;
mask_present =
get9_n_lessbits(
LEN_MASK_PRES,
pInputStream);
switch (mask_present)
{
case(MASK_NOT_PRESENT):
/* special EXTENDED_MS_MASK cases */
/* no ms at all */
break;
case(MASK_ALL_FRAME):
/* MS for whole spectrum on, mask bits set to 1 */
nwin = pFrameInfo->num_win;
for (win = 0; win < nwin; win = *(pGroup++))
{
for (sfb = pFrameInfo->sfb_per_win[win]; sfb > 0; sfb--)
{
*(pMask++) = 1; /* cannot use memset for Int type */
}
}
break;
case(MASK_FROM_BITSTREAM):
/* MS_mask_present==1, get mask information*/
nwin = pFrameInfo->num_win;
for (win = 0; win < nwin; win = *(pGroup++))
{
/*
* the following code is equivalent to
*
* for(sfb = max_sfb; sfb > 0; sfb--)
* {
* *(pMask++) =
* getbits(
* LEN_MASK,
* pInputStream);
* }
*
* in order to save the calls to getbits, the above
* for-loop is broken into two parts
*/
nToDo = max_sfb;
while (nToDo > 0)
{
nCall = nToDo;
if (nCall > MAX_GETBITS)
{
nCall = MAX_GETBITS;
}
tempMask =
getbits(
nCall,
pInputStream);
bitmask = (UInt32) 1 << (nCall - 1);
for (sfb = nCall; sfb > 0; sfb--)
{
*(pMask++) = (Int)((tempMask & bitmask) >> (sfb - 1));
bitmask >>= 1;
}
nToDo -= nCall;
}
/*
* set remaining sfbs to zero
* re-use nCall to save one variable on stack
*/
nCall = pFrameInfo->sfb_per_win[win] - max_sfb;
if (nCall >= 0)
{
pv_memset(pMask,
0,
nCall*sizeof(*pMask));
pMask += nCall;
}
else
{
mask_present = MASK_ERROR;
break;
}
} /* for (win) */
break;
default:
/* error */
break;
} /* switch (mask_present) */
return mask_present;
} /* getmask */
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