1/* 2 * RTJpeg decoding functions 3 * Copyright (c) 2006 Reimar Doeffinger 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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 "rtjpeg.h" 24 25#define PUT_COEFF(c) \ 26 i = scan[coeff--]; \ 27 block[i] = (c) * quant[i]; 28 29/// aligns the bitstream to the given power of two 30#define ALIGN(a) \ 31 n = (-get_bits_count(gb)) & (a - 1); \ 32 if (n) {skip_bits(gb, n);} 33 34/** 35 * @brief read one block from stream 36 * @param gb contains stream data 37 * @param block where data is written to 38 * @param scan array containing the mapping stream address -> block position 39 * @param quant quantization factors 40 * @return 0 means the block is not coded, < 0 means an error occurred. 41 * 42 * Note: GetBitContext is used to make the code simpler, since all data is 43 * aligned this could be done faster in a different way, e.g. as it is done 44 * in MPlayer libmpcodecs/native/rtjpegn.c. 45 */ 46static inline int get_block(GetBitContext *gb, int16_t *block, const uint8_t *scan, 47 const uint32_t *quant) { 48 int coeff, i, n; 49 int8_t ac; 50 uint8_t dc = get_bits(gb, 8); 51 52 // block not coded 53 if (dc == 255) 54 return 0; 55 56 // number of non-zero coefficients 57 coeff = get_bits(gb, 6); 58 if (get_bits_left(gb) < (coeff << 1)) 59 return AVERROR_INVALIDDATA; 60 61 // normally we would only need to clear the (63 - coeff) last values, 62 // but since we do not know where they are we just clear the whole block 63 memset(block, 0, 64 * sizeof(int16_t)); 64 65 // 2 bits per coefficient 66 while (coeff) { 67 ac = get_sbits(gb, 2); 68 if (ac == -2) 69 break; // continue with more bits 70 PUT_COEFF(ac); 71 } 72 73 // 4 bits per coefficient 74 ALIGN(4); 75 if (get_bits_left(gb) < (coeff << 2)) 76 return AVERROR_INVALIDDATA; 77 while (coeff) { 78 ac = get_sbits(gb, 4); 79 if (ac == -8) 80 break; // continue with more bits 81 PUT_COEFF(ac); 82 } 83 84 // 8 bits per coefficient 85 ALIGN(8); 86 if (get_bits_left(gb) < (coeff << 3)) 87 return AVERROR_INVALIDDATA; 88 while (coeff) { 89 ac = get_sbits(gb, 8); 90 PUT_COEFF(ac); 91 } 92 93 PUT_COEFF(dc); 94 return 1; 95} 96 97/** 98 * @brief decode one rtjpeg YUV420 frame 99 * @param c context, must be initialized via ff_rtjpeg_decode_init 100 * @param f AVFrame to place decoded frame into. If parts of the frame 101 * are not coded they are left unchanged, so consider initializing it 102 * @param buf buffer containing input data 103 * @param buf_size length of input data in bytes 104 * @return number of bytes consumed from the input buffer 105 */ 106int ff_rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f, 107 const uint8_t *buf, int buf_size) { 108 GetBitContext gb; 109 int w = c->w / 16, h = c->h / 16; 110 int x, y, ret; 111 uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0]; 112 uint8_t *u = f->data[1], *v = f->data[2]; 113 114 if ((ret = init_get_bits8(&gb, buf, buf_size)) < 0) 115 return ret; 116 117 for (y = 0; y < h; y++) { 118 for (x = 0; x < w; x++) { 119#define BLOCK(quant, dst, stride) do { \ 120 int res = get_block(&gb, block, c->scan, quant); \ 121 if (res < 0) \ 122 return res; \ 123 if (res > 0) \ 124 c->idsp.idct_put(dst, stride, block); \ 125} while (0) 126 int16_t *block = c->block; 127 BLOCK(c->lquant, y1, f->linesize[0]); 128 y1 += 8; 129 BLOCK(c->lquant, y1, f->linesize[0]); 130 y1 += 8; 131 BLOCK(c->lquant, y2, f->linesize[0]); 132 y2 += 8; 133 BLOCK(c->lquant, y2, f->linesize[0]); 134 y2 += 8; 135 BLOCK(c->cquant, u, f->linesize[1]); 136 u += 8; 137 BLOCK(c->cquant, v, f->linesize[2]); 138 v += 8; 139 } 140 y1 += 2 * 8 * (f->linesize[0] - w); 141 y2 += 2 * 8 * (f->linesize[0] - w); 142 u += 8 * (f->linesize[1] - w); 143 v += 8 * (f->linesize[2] - w); 144 } 145 return get_bits_count(&gb) / 8; 146} 147 148/** 149 * @brief initialize an RTJpegContext, may be called multiple times 150 * @param c context to initialize 151 * @param width width of image, will be rounded down to the nearest multiple 152 * of 16 for decoding 153 * @param height height of image, will be rounded down to the nearest multiple 154 * of 16 for decoding 155 * @param lquant luma quantization table to use 156 * @param cquant chroma quantization table to use 157 */ 158void ff_rtjpeg_decode_init(RTJpegContext *c, int width, int height, 159 const uint32_t *lquant, const uint32_t *cquant) { 160 int i; 161 for (i = 0; i < 64; i++) { 162 int p = c->idsp.idct_permutation[i]; 163 c->lquant[p] = lquant[i]; 164 c->cquant[p] = cquant[i]; 165 } 166 c->w = width; 167 c->h = height; 168} 169 170void ff_rtjpeg_init(RTJpegContext *c, AVCodecContext *avctx) 171{ 172 int i; 173 174 ff_idctdsp_init(&c->idsp, avctx); 175 176 for (i = 0; i < 64; i++) { 177 int z = ff_zigzag_direct[i]; 178 z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant 179 180 // permute the scan and quantization tables for the chosen idct 181 c->scan[i] = c->idsp.idct_permutation[z]; 182 } 183} 184