1/* 2 * RTJpeg decoding functions 3 * Copyright (c) 2006 Reimar Doeffinger 4 * 5 * This file is part of Libav. 6 * 7 * Libav is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * Libav is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with Libav; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21#include "libavutil/common.h" 22#include "get_bits.h" 23#include "dsputil.h" 24#include "rtjpeg.h" 25 26#define PUT_COEFF(c) \ 27 i = scan[coeff--]; \ 28 block[i] = (c) * quant[i]; 29 30/// aligns the bitstream to the given power of two 31#define ALIGN(a) \ 32 n = (-get_bits_count(gb)) & (a - 1); \ 33 if (n) {skip_bits(gb, n);} 34 35/** 36 * @brief read one block from stream 37 * @param gb contains stream data 38 * @param block where data is written to 39 * @param scan array containing the mapping stream address -> block position 40 * @param quant quantization factors 41 * @return 0 means the block is not coded, < 0 means an error occurred. 42 * 43 * Note: GetBitContext is used to make the code simpler, since all data is 44 * aligned this could be done faster in a different way, e.g. as it is done 45 * in MPlayer libmpcodecs/native/rtjpegn.c. 46 */ 47static inline int get_block(GetBitContext *gb, DCTELEM *block, const uint8_t *scan, 48 const uint32_t *quant) { 49 int coeff, i, n; 50 int8_t ac; 51 uint8_t dc = get_bits(gb, 8); 52 53 // block not coded 54 if (dc == 255) 55 return 0; 56 57 // number of non-zero coefficients 58 coeff = get_bits(gb, 6); 59 if (get_bits_left(gb) < (coeff << 1)) 60 return -1; 61 62 // normally we would only need to clear the (63 - coeff) last values, 63 // but since we do not know where they are we just clear the whole block 64 memset(block, 0, 64 * sizeof(DCTELEM)); 65 66 // 2 bits per coefficient 67 while (coeff) { 68 ac = get_sbits(gb, 2); 69 if (ac == -2) 70 break; // continue with more bits 71 PUT_COEFF(ac); 72 } 73 74 // 4 bits per coefficient 75 ALIGN(4); 76 if (get_bits_left(gb) < (coeff << 2)) 77 return -1; 78 while (coeff) { 79 ac = get_sbits(gb, 4); 80 if (ac == -8) 81 break; // continue with more bits 82 PUT_COEFF(ac); 83 } 84 85 // 8 bits per coefficient 86 ALIGN(8); 87 if (get_bits_left(gb) < (coeff << 3)) 88 return -1; 89 while (coeff) { 90 ac = get_sbits(gb, 8); 91 PUT_COEFF(ac); 92 } 93 94 PUT_COEFF(dc); 95 return 1; 96} 97 98/** 99 * @brief decode one rtjpeg YUV420 frame 100 * @param c context, must be initialized via rtjpeg_decode_init 101 * @param f AVFrame to place decoded frame into. If parts of the frame 102 * are not coded they are left unchanged, so consider initializing it 103 * @param buf buffer containing input data 104 * @param buf_size length of input data in bytes 105 * @return number of bytes consumed from the input buffer 106 */ 107int rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f, 108 const uint8_t *buf, int buf_size) { 109 GetBitContext gb; 110 int w = c->w / 16, h = c->h / 16; 111 int x, y; 112 uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0]; 113 uint8_t *u = f->data[1], *v = f->data[2]; 114 init_get_bits(&gb, buf, buf_size * 8); 115 for (y = 0; y < h; y++) { 116 for (x = 0; x < w; x++) { 117#define BLOCK(quant, dst, stride) do { \ 118 int res = get_block(&gb, block, c->scan, quant); \ 119 if (res < 0) \ 120 return res; \ 121 if (res > 0) \ 122 c->dsp->idct_put(dst, stride, block); \ 123} while (0) 124 DCTELEM *block = c->block; 125 BLOCK(c->lquant, y1, f->linesize[0]); 126 y1 += 8; 127 BLOCK(c->lquant, y1, f->linesize[0]); 128 y1 += 8; 129 BLOCK(c->lquant, y2, f->linesize[0]); 130 y2 += 8; 131 BLOCK(c->lquant, y2, f->linesize[0]); 132 y2 += 8; 133 BLOCK(c->cquant, u, f->linesize[1]); 134 u += 8; 135 BLOCK(c->cquant, v, f->linesize[2]); 136 v += 8; 137 } 138 y1 += 2 * 8 * (f->linesize[0] - w); 139 y2 += 2 * 8 * (f->linesize[0] - w); 140 u += 8 * (f->linesize[1] - w); 141 v += 8 * (f->linesize[2] - w); 142 } 143 return get_bits_count(&gb) / 8; 144} 145 146/** 147 * @brief initialize an RTJpegContext, may be called multiple times 148 * @param c context to initialize 149 * @param dsp specifies the idct to use for decoding 150 * @param width width of image, will be rounded down to the nearest multiple 151 * of 16 for decoding 152 * @param height height of image, will be rounded down to the nearest multiple 153 * of 16 for decoding 154 * @param lquant luma quantization table to use 155 * @param cquant chroma quantization table to use 156 */ 157void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp, 158 int width, int height, 159 const uint32_t *lquant, const uint32_t *cquant) { 160 int i; 161 c->dsp = dsp; 162 for (i = 0; i < 64; i++) { 163 int z = ff_zigzag_direct[i]; 164 int p = c->dsp->idct_permutation[i]; 165 z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant 166 167 // permute the scan and quantization tables for the chosen idct 168 c->scan[i] = c->dsp->idct_permutation[z]; 169 c->lquant[p] = lquant[i]; 170 c->cquant[p] = cquant[i]; 171 } 172 c->w = width; 173 c->h = height; 174} 175