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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: getfill.c
Funtions: getfill
------------------------------------------------------------------------------
REVISION HISTORY
Description: Modified from original shareware code
Description: Modified to pass variables by reference to eliminate use
of global variables.
Description: 1. Used template to re-organize function and filled out
Input/Output and Function definition section.
2. Optimized code.
Description: Made the following changes based on review comments.
1. Exchanging MODIFYING and RETURNING on line 87, 88.
2. Added MPEG reference.
3. Changed "fill" to "pass over", "bitstreams are" to
"bitstream is" in FUNCTION DESCRIPTION section.
4. Fixed tabs.
Description: Replace some instances of getbits to get9_n_lessbits
when the number of bits read is 9 or less.
Who: Date:
Description:
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
pInputStream = pointer to structure BITS containing input stream
information.
Local Stores/Buffers/Pointers Needed:
None
Global Stores/Buffers/Pointers Needed:
None
Outputs:
None
Pointers and Buffers Modified:
pInputStream->usedBits is updated to the newly calculated value.
Local Stores Modified:
None
Global Stores Modified:
None
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
This function passes over fill bits in the raw data block to adjust the
instantaneous bit rate when the bitstream is to be transmitted over a
constant rate channel.
------------------------------------------------------------------------------
REQUIREMENTS
None
------------------------------------------------------------------------------
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 4.4.11)
------------------------------------------------------------------------------
PSEUDO-CODE
CALL getbits(
LEN_F_CNT,
pInputStream);
MODIFYING (pInputStream)
RETURNING (cnt)
IF ( cnt == (1<<LEN_F_CNT)-1 )
CALL getbits(
LEN_F_ESC,
pInputStream);
MODIFYING (pInputStream)
RETURNING (esc_cnt)
cnt += esc_cnt - 1;
ENDIF
pInputStream->usedBits += cnt * LEN_BYTE;
------------------------------------------------------------------------------
RESOURCES USED
When the code is written for a specific target processor the
the resources used should be documented below.
STACK USAGE: [stack count for this module] + [variable to represent
stack usage for each subroutine called]
where: [stack usage variable] = stack usage for [subroutine
name] (see [filename].ext)
DATA MEMORY USED: x words
PROGRAM MEMORY USED: x words
CLOCK CYCLES: [cycle count equation for this module] + [variable
used to represent cycle count for each subroutine
called]
where: [cycle count variable] = cycle count for [subroutine
name] (see [filename].ext)
------------------------------------------------------------------------------
*/
/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "pv_audio_type_defs.h"
#include "s_bits.h"
#include "ibstream.h"
#include "e_rawbitstreamconst.h"
#include "getfill.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 VARIABLE 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
----------------------------------------------------------------------------*/
void getfill(BITS *pInputStream)
{
/*----------------------------------------------------------------------------
; Define all local variables
----------------------------------------------------------------------------*/
Int cnt;
Int esc_cnt;
/*----------------------------------------------------------------------------
; Function body here
----------------------------------------------------------------------------*/
cnt = get9_n_lessbits(
LEN_F_CNT,
pInputStream);
if (cnt == (1 << LEN_F_CNT) - 1) /* if (cnt == 15) */
{
esc_cnt = get9_n_lessbits(
LEN_F_ESC,
pInputStream);
cnt += esc_cnt - 1;
}
/*
* The following codes are replaced by directly updating usedBits
* in BITS structure. This will save one call for getbits().
*
* for (i=0; i<cnt; i++)
* { getbits(LEN_BYTE, pInputStream); }
*/
pInputStream->usedBits += cnt * LEN_BYTE;
/*----------------------------------------------------------------------------
; Return nothing or data or data pointer
----------------------------------------------------------------------------*/
} /* getfill */
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