1 /****************************************************************************** 2 * 3 * Copyright (C) 2015 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ***************************************************************************** 18 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore 19 */ 20 21 /*! 22 ************************************************************************** 23 * \file ih264d_bitstrm.c 24 * 25 * \brief 26 * Bitstream parsing routines 27 * 28 * \date 29 * 20/11/2002 30 * 31 * \author AI 32 ************************************************************************** 33 */ 34 35 #include <stdlib.h> 36 #include "ih264_typedefs.h" 37 #include "ih264_macros.h" 38 #include "ih264_platform_macros.h" 39 #include "ih264d_bitstrm.h" 40 #include "ih264d_error_handler.h" 41 42 #include "ih264d_debug.h" 43 #include "ih264d_tables.h" 44 #include "ih264d_structs.h" 45 46 /*! 47 ************************************************************************** 48 * \if Function name : ih264d_get_bit_h264 \endif 49 * 50 * \brief 51 * Read one bit from the bitstream. 52 * 53 * This is a Bitstream processing function. It reads the 54 * bit currently pointed by the bit pointer in the 55 * buffer and advances the pointer by one. It returns 56 * the bit (0 or 1) in the form of an unsigned integer. 57 * 58 * \return 59 * Returns the next bit (0 or 1) in the bitstream. 60 * 61 ************************************************************************** 62 */ 63 UWORD8 ih264d_get_bit_h264(dec_bit_stream_t *ps_stream) 64 { 65 UWORD32 u4_code; 66 67 GETBIT(u4_code, ps_stream->u4_ofst, ps_stream->pu4_buffer); 68 return (u4_code); 69 } 70 71 /*! 72 ************************************************************************** 73 * \if Function name : ih264d_get_bits_h264 \endif 74 * 75 * \brief 76 * Read specified number of bits from the bitstream. 77 * 78 * This is a Bitstream processing function. It reads the 79 * number specified number of bits from the current bit 80 * position and advances the bit and byte pointers 81 * appropriately. 82 * 83 * \return 84 * An unsigned 32 bit integer with its least significant bits 85 * containing the bits in order of their occurence in the bitstream. 86 * 87 ************************************************************************** 88 */ 89 90 UWORD32 ih264d_get_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits) 91 { 92 UWORD32 u4_code = 0; 93 if(u4_num_bits) 94 GETBITS(u4_code, ps_bitstrm->u4_ofst, ps_bitstrm->pu4_buffer, u4_num_bits); 95 return (u4_code); 96 } 97 98 /*! 99 ************************************************************************** 100 * \if Function name : ih264d_next_bits_h264 \endif 101 * 102 * \brief 103 * Peek specified number of bits from the bitstream. 104 * 105 * This is a Bitstream processing function. It gets the 106 * specified number of bits from the buffer without 107 * altering the current pointers. It is equivalent to 108 * next_bits() function in the standard. 109 * 110 * \return 111 * An unsigned 32 bit integer with its least significant bits 112 * containing the bits in order of their occurence in the bitstream. 113 ************************************************************************** 114 */ 115 UWORD32 ih264d_next_bits_h264(dec_bit_stream_t *ps_bitstrm, UWORD32 u4_num_bits) 116 { 117 UWORD32 u4_word_off = (ps_bitstrm->u4_ofst >> 5); 118 UWORD32 u4_bit_off = ps_bitstrm->u4_ofst & 0x1F; 119 UWORD32 *pu4_bitstream = ps_bitstrm->pu4_buffer; 120 UWORD32 u4_bits = pu4_bitstream[u4_word_off++] << u4_bit_off; 121 122 /*************************************************************************/ 123 /* Test if number of bits to be read exceeds the number of bits in the */ 124 /* current word. If yes, read from the next word of the buffer, The bits */ 125 /* from both the words are concatenated to get next 32 bits in 'u4_bits' */ 126 /*************************************************************************/ 127 if(u4_bit_off > (INT_IN_BITS - u4_num_bits)) 128 u4_bits |= (pu4_bitstream[u4_word_off] >> (INT_IN_BITS - u4_bit_off)); 129 130 return ((u4_bits >> (INT_IN_BITS - u4_num_bits))); 131 } 132 133 /*! 134 ************************************************************************** 135 * \if Function name : ih264d_flush_bits_h264 \endif 136 * 137 * \brief 138 * Flush specified number of bits from the bitstream. 139 * 140 * This function flushes the specified number of bits (marks 141 * as read) from the buffer. 142 * 143 * \return 144 * A 8 bit unsigned integer with value 145 * '1' on successful flush 146 * '0' on failure. 147 * 148 ************************************************************************** 149 */ 150 WORD32 ih264d_flush_bits_h264(dec_bit_stream_t *ps_bitstrm, WORD32 u4_num_bits) 151 { 152 ps_bitstrm->u4_ofst += u4_num_bits; 153 154 if(ps_bitstrm->u4_ofst > ps_bitstrm->u4_max_ofst) 155 { 156 return ERROR_EOB_FLUSHBITS_T; 157 } 158 return OK; 159 } 160 161 /*! 162 ************************************************************************** 163 * \if Function name : ih264d_check_byte_aligned \endif 164 * 165 * \brief 166 * Checks whether the bit ps_bitstrm u4_ofst is at byte boundary. 167 * 168 * \param ps_bitstrm : Pointer to bitstream 169 * 170 * \return 171 * Returns 1 if bit ps_bitstrm u4_ofst is at byte alligned position else zero. 172 ************************************************************************** 173 */ 174 175 UWORD8 ih264d_check_byte_aligned(dec_bit_stream_t * ps_bitstrm) 176 { 177 if(ps_bitstrm->u4_ofst & 0x07) 178 return (0); 179 else 180 return (1); 181 } 182
