| 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 | */ |
| 46 | static 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 | */ |
| 106 | int 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 | */ |
| 158 | void 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 | |
| 170 | void 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 | } |