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182 lines
5.7 KiB
C
182 lines
5.7 KiB
C
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/******************************************************************************
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*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*****************************************************************************
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* Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore
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*/
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/*!
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**************************************************************************
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* \file ih264d_bitstrm.c
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*
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* \brief
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* Bitstream parsing routines
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*
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* \date
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* 20/11/2002
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*
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* \author AI
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**************************************************************************
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*/
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#include <stdlib.h>
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#include "ih264_typedefs.h"
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#include "ih264_macros.h"
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#include "ih264_platform_macros.h"
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#include "ih264d_bitstrm.h"
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#include "ih264d_error_handler.h"
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#include "ih264d_debug.h"
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#include "ih264d_tables.h"
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#include "ih264d_structs.h"
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/*!
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**************************************************************************
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* \if Function name : ih264d_get_bit_h264 \endif
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*
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* \brief
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* Read one bit from the bitstream.
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*
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* This is a Bitstream processing function. It reads the
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* bit currently pointed by the bit pointer in the
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* buffer and advances the pointer by one. It returns
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* the bit (0 or 1) in the form of an unsigned integer.
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*
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* \return
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* Returns the next bit (0 or 1) in the bitstream.
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*
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**************************************************************************
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*/
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UWORD8 ih264d_get_bit_h264(dec_bit_stream_t *ps_stream)
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{
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UWORD32 u4_code;
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GETBIT(u4_code, ps_stream->u4_ofst, ps_stream->pu4_buffer);
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return (u4_code);
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}
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/*!
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**************************************************************************
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* \if Function name : ih264d_get_bits_h264 \endif
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*
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* \brief
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* Read specified number of bits from the bitstream.
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*
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* This is a Bitstream processing function. It reads the
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* number specified number of bits from the current bit
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* position and advances the bit and byte pointers
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* appropriately.
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*
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* \return
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* An unsigned 32 bit integer with its least significant bits
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* containing the bits in order of their occurence in the bitstream.
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*
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**************************************************************************
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*/
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UWORD32 ih264d_get_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits)
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{
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UWORD32 u4_code = 0;
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if(u4_num_bits)
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GETBITS(u4_code, ps_bitstrm->u4_ofst, ps_bitstrm->pu4_buffer, u4_num_bits);
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return (u4_code);
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}
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/*!
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**************************************************************************
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* \if Function name : ih264d_next_bits_h264 \endif
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*
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* \brief
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* Peek specified number of bits from the bitstream.
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*
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* This is a Bitstream processing function. It gets the
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* specified number of bits from the buffer without
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* altering the current pointers. It is equivalent to
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* next_bits() function in the standard.
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*
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* \return
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* An unsigned 32 bit integer with its least significant bits
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* containing the bits in order of their occurence in the bitstream.
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**************************************************************************
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*/
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UWORD32 ih264d_next_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits)
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{
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UWORD32 u4_word_off = (ps_bitstrm->u4_ofst >> 5);
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UWORD32 u4_bit_off = ps_bitstrm->u4_ofst & 0x1F;
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UWORD32 *pu4_bitstream = ps_bitstrm->pu4_buffer;
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UWORD32 u4_bits = pu4_bitstream[u4_word_off++] << u4_bit_off;
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/*************************************************************************/
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/* Test if number of bits to be read exceeds the number of bits in the */
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/* current word. If yes, read from the next word of the buffer, The bits */
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/* from both the words are concatenated to get next 32 bits in 'u4_bits' */
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/*************************************************************************/
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if(u4_bit_off > (INT_IN_BITS - u4_num_bits))
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u4_bits |= (pu4_bitstream[u4_word_off] >> (INT_IN_BITS - u4_bit_off));
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return ((u4_bits >> (INT_IN_BITS - u4_num_bits)));
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}
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/*!
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**************************************************************************
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* \if Function name : ih264d_flush_bits_h264 \endif
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*
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* \brief
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* Flush specified number of bits from the bitstream.
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*
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* This function flushes the specified number of bits (marks
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* as read) from the buffer.
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*
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* \return
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* A 8 bit unsigned integer with value
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* '1' on successful flush
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* '0' on failure.
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*
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**************************************************************************
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*/
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WORD32 ih264d_flush_bits_h264(dec_bit_stream_t *ps_bitstrm, WORD32 u4_num_bits)
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{
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ps_bitstrm->u4_ofst += u4_num_bits;
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if(ps_bitstrm->u4_ofst > ps_bitstrm->u4_max_ofst)
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{
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return ERROR_EOB_FLUSHBITS_T;
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}
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return OK;
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}
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/*!
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**************************************************************************
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* \if Function name : ih264d_check_byte_aligned \endif
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*
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* \brief
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* Checks whether the bit ps_bitstrm u4_ofst is at byte boundary.
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*
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* \param ps_bitstrm : Pointer to bitstream
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*
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* \return
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* Returns 1 if bit ps_bitstrm u4_ofst is at byte alligned position else zero.
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**************************************************************************
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*/
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UWORD8 ih264d_check_byte_aligned(dec_bit_stream_t * ps_bitstrm)
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{
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if(ps_bitstrm->u4_ofst & 0x07)
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return (0);
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else
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return (1);
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}
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