1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 /** 17 ************************************************************************ 18 * @file M4_BitStreamParser.h 19 * @brief MPEG-4 File Format bit stream utility 20 * @note This file contains utility functions used to parse MPEG specific 21 * data structures. 22 ************************************************************************ 23 */ 24 #ifndef __M4_BITSTREAMPARSER_H__ 25 #define __M4_BITSTREAMPARSER_H__ 26 27 #include "M4OSA_Types.h" 28 29 /** 30 * M4_BitStreamParser_Init. 31 * 32 * Allocates the context and initializes internal data 33 * 34 * @param pContext : A pointer to the context internally used by the package - ALLOCATED BY THE 35 * FUNCTION (M4OSA_NULL if allocation fails) 36 * @param bitStream : A pointer to the bitstream - must be 32 bits as access are 32 bits 37 * @param size : The size of the bitstream in bytes 38 * 39 */ 40 void M4_BitStreamParser_Init(void** pContext, void* pBitStream, M4OSA_Int32 size); 41 42 /** 43 ************************************************************************ 44 * @brief Clean up context 45 * @param pContext (IN/OUT) M4_BitStreamParser context. 46 ************************************************************************ 47 */ 48 void M4_BitStreamParser_CleanUp(void* pContext); 49 50 /** 51 ************************************************************************ 52 * @brief Read the next <length> bits in the bitstream. 53 * @note The function does not update the bitstream pointer. 54 * @param pContext (IN/OUT) M4_BitStreamParser context. 55 * @param length (IN) The number of bits to extract from the bitstream 56 * @return the read bits 57 ************************************************************************ 58 */ 59 M4OSA_UInt32 M4_BitStreamParser_ShowBits(void* pContext, M4OSA_Int32 length); 60 61 /** 62 ************************************************************************ 63 * @brief Increment the bitstream pointer of <length> bits. 64 * @param pContext (IN/OUT) M4_BitStreamParser context. 65 * @param length (IN) The number of bit to shift the bitstream 66 ************************************************************************ 67 */ 68 void M4_BitStreamParser_FlushBits(void* pContext, M4OSA_Int32 length); 69 70 /** 71 ************************************************************************ 72 * @brief Get a pointer to the current byte pointed by the bitstream pointer. 73 * It does not update the bitstream pointer 74 * 75 * @param pContext : A pointer to the context internally used by the package 76 * @param length : The number of bit to extract from the bitstream 77 * 78 * @returns the read bits 79 */ 80 M4OSA_UInt32 M4_BitStreamParser_GetBits(void* pContext,M4OSA_Int32 bitPos, M4OSA_Int32 length); 81 82 /** 83 * M4_BitStreamParser_Restart resets the bitstream indexes. 84 * 85 * @param pContext : A pointer to the context internally used by the package 86 * 87 */ 88 void M4_BitStreamParser_Restart(void* pContext); 89 90 /** 91 ************************************************************************ 92 * @brief Get a pointer to the current byte pointed by the bitstream pointer. 93 * @returns pointer to the current location in the bitstream 94 * @note It should be used carefully as the pointer is in the bitstream itself 95 * and no copy is made. 96 * @param pContext (IN/OUT) M4_BitStreamParser context. 97 */ 98 M4OSA_UInt8* M4_BitStreamParser_GetCurrentbitStreamPointer(void* pContext); 99 100 /** 101 * M4_BitStreamParser_GetSize gets the size of the bitstream in bytes 102 * 103 * @param pContext : A pointer to the context internally used by the package 104 * 105 * @returns the size of the bitstream in bytes 106 */ 107 M4OSA_Int32 M4_BitStreamParser_GetSize(void* pContext); 108 109 void M4_MPEG4BitStreamParser_Init(void** pContext, void* pBitStream, M4OSA_Int32 size); 110 111 /** 112 * getMpegLengthFromInteger returns a decoded size value from an encoded one (SDL) 113 * 114 * @param pContext : A pointer to the context internally used by the package 115 * @param val : encoded value 116 * 117 * @returns size in a human readable form 118 */ 119 120 M4OSA_Int32 M4_MPEG4BitStreamParser_GetMpegLengthFromInteger(void* pContext, M4OSA_UInt32 val); 121 122 123 /** 124 ************************************************************************ 125 * @brief Decode an MPEG4 Systems descriptor size from an encoded SDL size data. 126 * @note The value is read from the current bitstream location. 127 * @param pContext (IN/OUT) M4_BitStreamParser context. 128 * @return Size in a human readable form 129 ************************************************************************ 130 */ 131 M4OSA_Int32 M4_MPEG4BitStreamParser_GetMpegLengthFromStream(void* pContext); 132 133 #endif /*__M4_BITSTREAMPARSER_H__*/ 134 135
