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 "bitstream.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 * 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, DCTELEM *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 // normally we would only need to clear the (63 - coeff) last values, 59 // but since we do not know where they are we just clear the whole block 60 memset(block, 0, 64 * sizeof(DCTELEM)); 61 62 // 2 bits per coefficient 63 while (coeff) { 64 ac = get_sbits(gb, 2); 65 if (ac == -2) 66 break; // continue with more bits 67 PUT_COEFF(ac); 68 } 69 70 // 4 bits per coefficient 71 ALIGN(4); 72 while (coeff) { 73 ac = get_sbits(gb, 4); 74 if (ac == -8) 75 break; // continue with more bits 76 PUT_COEFF(ac); 77 } 78 79 // 8 bits per coefficient 80 ALIGN(8); 81 while (coeff) { 82 ac = get_sbits(gb, 8); 83 PUT_COEFF(ac); 84 } 85 86 PUT_COEFF(dc); 87 return 1; 88} 89 90/** 91 * \brief decode one rtjpeg YUV420 frame 92 * \param c context, must be initialized via rtjpeg_decode_init 93 * \param f AVFrame to place decoded frame into. If parts of the frame 94 * are not coded they are left unchanged, so consider initializing it 95 * \param buf buffer containing input data 96 * \param buf_size length of input data in bytes 97 * \return number of bytes consumed from the input buffer 98 */ 99int rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f, 100 const uint8_t *buf, int buf_size) { 101 DECLARE_ALIGNED_16(DCTELEM, block[64]); 102 GetBitContext gb; 103 int w = c->w / 16, h = c->h / 16; 104 int x, y; 105 uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0]; 106 uint8_t *u = f->data[1], *v = f->data[2]; 107 init_get_bits(&gb, buf, buf_size * 8); 108 for (y = 0; y < h; y++) { 109 for (x = 0; x < w; x++) { 110 if (get_block(&gb, block, c->scan, c->lquant)) 111 c->dsp->idct_put(y1, f->linesize[0], block); 112 y1 += 8; 113 if (get_block(&gb, block, c->scan, c->lquant)) 114 c->dsp->idct_put(y1, f->linesize[0], block); 115 y1 += 8; 116 if (get_block(&gb, block, c->scan, c->lquant)) 117 c->dsp->idct_put(y2, f->linesize[0], block); 118 y2 += 8; 119 if (get_block(&gb, block, c->scan, c->lquant)) 120 c->dsp->idct_put(y2, f->linesize[0], block); 121 y2 += 8; 122 if (get_block(&gb, block, c->scan, c->cquant)) 123 c->dsp->idct_put(u, f->linesize[1], block); 124 u += 8; 125 if (get_block(&gb, block, c->scan, c->cquant)) 126 c->dsp->idct_put(v, f->linesize[2], block); 127 v += 8; 128 } 129 y1 += 2 * 8 * (f->linesize[0] - w); 130 y2 += 2 * 8 * (f->linesize[0] - w); 131 u += 8 * (f->linesize[1] - w); 132 v += 8 * (f->linesize[2] - w); 133 } 134 return get_bits_count(&gb) / 8; 135} 136 137/** 138 * \brief initialize an RTJpegContext, may be called multiple times 139 * \param c context to initialize 140 * \param dsp specifies the idct to use for decoding 141 * \param width width of image, will be rounded down to the nearest multiple 142 * of 16 for decoding 143 * \param height height of image, will be rounded down to the nearest multiple 144 * of 16 for decoding 145 * \param lquant luma quantization table to use 146 * \param cquant chroma quantization table to use 147 */ 148void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp, 149 int width, int height, 150 const uint32_t *lquant, const uint32_t *cquant) { 151 int i; 152 c->dsp = dsp; 153 for (i = 0; i < 64; i++) { 154 int z = ff_zigzag_direct[i]; 155 int p = c->dsp->idct_permutation[i]; 156 z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant 157 158 // permute the scan and quantization tables for the chosen idct 159 c->scan[i] = c->dsp->idct_permutation[z]; 160 c->lquant[p] = lquant[i]; 161 c->cquant[p] = cquant[i]; 162 } 163 c->w = width; 164 c->h = height; 165} 166