1 /* ------------------------------------------------------------------ 2 * Copyright (C) 1998-2009 PacketVideo 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 13 * express or implied. 14 * See the License for the specific language governing permissions 15 * and limitations under the License. 16 * ------------------------------------------------------------------- 17 */ 18 #include "mp4dec_lib.h" 19 #include "vlc_decode.h" 20 #include "bitstream.h" 21 #include "zigzag.h" 22 23 PV_STATUS PV_DecodePredictedIntraDC( 24 int compnum, 25 BitstreamDecVideo *stream, 26 int16 *INTRADC_delta) 27 { 28 29 /*---------------------------------------------------------------------------- 30 ; Define all local variables 31 ----------------------------------------------------------------------------*/ 32 PV_STATUS status = PV_SUCCESS; 33 uint DC_size; 34 uint code; 35 int first_bit; 36 37 /*---------------------------------------------------------------------------- 38 ; Function body here 39 ----------------------------------------------------------------------------*/ 40 /* read DC size 2 - 8 bits */ 41 status = PV_VlcDecIntraDCPredSize(stream, compnum, &DC_size); 42 43 if (status == PV_SUCCESS) 44 { 45 if (DC_size == 0) 46 { 47 *INTRADC_delta = 0; 48 } 49 else 50 { 51 /* read delta DC 0 - 8 bits */ 52 code = (int) BitstreamReadBits16_INLINE(stream, DC_size); 53 54 first_bit = code >> (DC_size - 1); 55 56 if (first_bit == 0) 57 { 58 /* negative delta INTRA DC */ 59 *INTRADC_delta = code ^((1 << DC_size) - 1); 60 *INTRADC_delta = -(*INTRADC_delta); 61 } 62 else 63 { /* positive delta INTRA DC */ 64 *INTRADC_delta = code; 65 } 66 if (DC_size > 8) BitstreamRead1Bits_INLINE(stream); 67 } 68 } 69 70 /*---------------------------------------------------------------------------- 71 ; Return nothing or data or data pointer 72 ----------------------------------------------------------------------------*/ 73 return status; 74 } 75 76
