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 "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 give 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_count(gb) + (coeff << 1) >= gb->size_in_bits) 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_count(gb) + (coeff << 2) >= gb->size_in_bits) 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_count(gb) + (coeff << 3) >= gb->size_in_bits) 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 DCTELEM *block = c->block; 118 if (get_block(&gb, block, c->scan, c->lquant) > 0) 119 c->dsp->idct_put(y1, f->linesize[0], block); 120 y1 += 8; 121 if (get_block(&gb, block, c->scan, c->lquant) > 0) 122 c->dsp->idct_put(y1, f->linesize[0], block); 123 y1 += 8; 124 if (get_block(&gb, block, c->scan, c->lquant) > 0) 125 c->dsp->idct_put(y2, f->linesize[0], block); 126 y2 += 8; 127 if (get_block(&gb, block, c->scan, c->lquant) > 0) 128 c->dsp->idct_put(y2, f->linesize[0], block); 129 y2 += 8; 130 if (get_block(&gb, block, c->scan, c->cquant) > 0) 131 c->dsp->idct_put(u, f->linesize[1], block); 132 u += 8; 133 if (get_block(&gb, block, c->scan, c->cquant) > 0) 134 c->dsp->idct_put(v, f->linesize[2], block); 135 v += 8; 136 } 137 y1 += 2 * 8 * (f->linesize[0] - w); 138 y2 += 2 * 8 * (f->linesize[0] - w); 139 u += 8 * (f->linesize[1] - w); 140 v += 8 * (f->linesize[2] - w); 141 } 142 return get_bits_count(&gb) / 8; 143} 144 145/** 146 * \brief initialize an RTJpegContext, may be called multiple times 147 * \param c context to initialize 148 * \param dsp specifies the idct to use for decoding 149 * \param width width of image, will be rounded down to the nearest multiple 150 * of 16 for decoding 151 * \param height height of image, will be rounded down to the nearest multiple 152 * of 16 for decoding 153 * \param lquant luma quantization table to use 154 * \param cquant chroma quantization table to use 155 */ 156void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp, 157 int width, int height, 158 const uint32_t *lquant, const uint32_t *cquant) { 159 int i; 160 c->dsp = dsp; 161 for (i = 0; i < 64; i++) { 162 int z = ff_zigzag_direct[i]; 163 int p = c->dsp->idct_permutation[i]; 164 z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant 165 166 // permute the scan and quantization tables for the chosen idct 167 c->scan[i] = c->dsp->idct_permutation[z]; 168 c->lquant[p] = lquant[i]; 169 c->cquant[p] = cquant[i]; 170 } 171 c->w = width; 172 c->h = height; 173} 174