1 /* 2 * Copyright (C) 2007-2008 ARM Limited 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 * 19 * File Name: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC.c 20 * OpenMAX DL: v1.0.2 21 * Revision: 9641 22 * Date: Thursday, February 7, 2008 23 * 24 * 25 * 26 * 27 * Description: 28 * Contains modules for zigzag scanning and VLC decoding 29 * for intra block. 30 * 31 */ 32 33 #include "omxtypes.h" 34 #include "armOMX.h" 35 #include "omxVC.h" 36 37 #include "armVC.h" 38 #include "armCOMM_Bitstream.h" 39 #include "armCOMM.h" 40 #include "armVCM4P2_Huff_Tables_VLC.h" 41 #include "armVCM4P2_ZigZag_Tables.h" 42 43 44 45 46 /** 47 * Function: omxVCM4P2_DecodeVLCZigzag_IntraDCVLC (6.2.5.2.2) 48 * 49 * Description: 50 * Performs VLC decoding and inverse zigzag scan of AC and DC coefficients 51 * for one intra block. Two versions of the function (DCVLC and ACVLC) are 52 * provided in order to support the two different methods of processing DC 53 * coefficients, as described in [ISO14496-2], subclause 7.4.1.4, Intra DC 54 * Coefficient Decoding for the Case of Switched VLC Encoding. 55 * 56 * Input Arguments: 57 * 58 * ppBitStream - pointer to the pointer to the current byte in the 59 * bitstream buffer 60 * pBitOffset - pointer to the bit position in the current byte referenced 61 * by *ppBitStream. The parameter *pBitOffset is valid in the 62 * range [0-7]. 63 * Bit Position in one byte: |Most Least| 64 * *pBitOffset |0 1 2 3 4 5 6 7| 65 * predDir - AC prediction direction; used to select the zigzag scan 66 * pattern; takes one of the following values: 67 * - OMX_VC_NONE - AC prediction not used; 68 * performs classical zigzag scan. 69 * - OMX_VC_HORIZONTAL - Horizontal prediction; 70 * performs alternate-vertical zigzag scan; 71 * - OMX_VC_VERTICAL - Vertical prediction; 72 * performs alternate-horizontal zigzag scan. 73 * shortVideoHeader - binary flag indicating presence of 74 * short_video_header; escape modes 0-3 are used if 75 * shortVideoHeader==0, and escape mode 4 is used when 76 * shortVideoHeader==1. 77 * videoComp - video component type (luminance or chrominance) of the 78 * current block 79 * 80 * Output Arguments: 81 * 82 * ppBitStream - *ppBitStream is updated after the block is decoded such 83 * that it points to the current byte in the bit stream buffer 84 * pBitOffset - *pBitOffset is updated such that it points to the current 85 * bit position in the byte pointed by *ppBitStream 86 * pDst - pointer to the coefficient buffer of current block; must be 87 * 4-byte aligned. 88 * 89 * Return Value: 90 * 91 * OMX_Sts_NoErr - no error 92 * OMX_Sts_BadArgErr - bad arguments, if: 93 * - At least one of the following pointers is NULL: 94 * ppBitStream, *ppBitStream, pBitOffset, pDst 95 * - *pBitOffset exceeds [0,7] 96 * - preDir exceeds [0,2] 97 * - pDst is not 4-byte aligned 98 * OMX_Sts_Err - if: 99 * - In DecodeVLCZigzag_IntraDCVLC, dc_size > 12 100 * - At least one of mark bits equals zero 101 * - Illegal stream encountered; code cannot be located in VLC table 102 * - Forbidden code encountered in the VLC FLC table. 103 * - The number of coefficients is greater than 64 104 * 105 */ 106 107 OMXResult omxVCM4P2_DecodeVLCZigzag_IntraDCVLC( 108 const OMX_U8 ** ppBitStream, 109 OMX_INT * pBitOffset, 110 OMX_S16 * pDst, 111 OMX_U8 predDir, 112 OMX_INT shortVideoHeader, 113 OMXVCM4P2VideoComponent videoComp 114 ) 115 { 116 /* Dummy initilaization to remove compilation error */ 117 OMX_S8 DCValueSize = 0; 118 OMX_U16 powOfSize, fetchDCbits; 119 OMX_U8 start = 1; 120 121 /* Argument error checks */ 122 armRetArgErrIf(ppBitStream == NULL, OMX_Sts_BadArgErr); 123 armRetArgErrIf(*ppBitStream == NULL, OMX_Sts_BadArgErr); 124 armRetArgErrIf(pBitOffset == NULL, OMX_Sts_BadArgErr); 125 armRetArgErrIf(pDst == NULL, OMX_Sts_BadArgErr); 126 armRetArgErrIf(!armIs4ByteAligned(pDst), OMX_Sts_BadArgErr); 127 armRetArgErrIf((*pBitOffset < 0) || (*pBitOffset > 7), OMX_Sts_BadArgErr); 128 armRetArgErrIf((predDir > 2), OMX_Sts_BadArgErr); 129 130 /* Insert the code into the bitstream */ 131 if (videoComp == OMX_VC_LUMINANCE) 132 { 133 DCValueSize = armUnPackVLC32(ppBitStream, 134 pBitOffset, armVCM4P2_aIntraDCLumaIndex); 135 } 136 else if (videoComp == OMX_VC_CHROMINANCE) 137 { 138 DCValueSize = armUnPackVLC32(ppBitStream, 139 pBitOffset, armVCM4P2_aIntraDCChromaIndex); 140 } 141 armRetDataErrIf(DCValueSize == -1, OMX_Sts_Err); 142 armRetDataErrIf(DCValueSize > 12, OMX_Sts_Err); 143 144 145 if (DCValueSize == 0) 146 { 147 pDst[0] = 0; 148 } 149 else 150 { 151 fetchDCbits = (OMX_U16) armGetBits(ppBitStream, pBitOffset, \ 152 DCValueSize); 153 154 if ( (fetchDCbits >> (DCValueSize - 1)) == 0) 155 { 156 /* calulate pow */ 157 powOfSize = (1 << DCValueSize); 158 159 pDst[0] = (OMX_S16) (fetchDCbits ^ (powOfSize - 1)); 160 pDst[0] = -pDst[0]; 161 } 162 else 163 { 164 pDst[0] = fetchDCbits; 165 } 166 167 if (DCValueSize > 8) 168 { 169 /* reading and checking the marker bit*/ 170 armRetDataErrIf (armGetBits(ppBitStream, pBitOffset, 1) == 0, \ 171 OMX_Sts_Err); 172 } 173 } 174 175 return armVCM4P2_DecodeVLCZigzag_Intra( 176 ppBitStream, 177 pBitOffset, 178 pDst, 179 predDir, 180 shortVideoHeader, 181 start); 182 } 183 184 /* End of file */ 185 186
