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4349 | Serge | 1 | /* |
2 | * RTJpeg decoding functions |
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3 | * Copyright (c) 2006 Reimar Doeffinger |
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4 | * |
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5 | * This file is part of FFmpeg. |
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6 | * |
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7 | * FFmpeg is free software; you can redistribute it and/or |
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8 | * modify it under the terms of the GNU Lesser General Public |
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9 | * License as published by the Free Software Foundation; either |
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10 | * version 2.1 of the License, or (at your option) any later version. |
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11 | * |
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12 | * FFmpeg is distributed in the hope that it will be useful, |
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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15 | * Lesser General Public License for more details. |
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16 | * |
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17 | * You should have received a copy of the GNU Lesser General Public |
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18 | * License along with FFmpeg; if not, write to the Free Software |
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19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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20 | */ |
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21 | #include "libavutil/common.h" |
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22 | #include "get_bits.h" |
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23 | #include "rtjpeg.h" |
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24 | |||
25 | #define PUT_COEFF(c) \ |
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26 | i = scan[coeff--]; \ |
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27 | block[i] = (c) * quant[i]; |
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28 | |||
29 | /// aligns the bitstream to the given power of two |
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30 | #define ALIGN(a) \ |
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31 | n = (-get_bits_count(gb)) & (a - 1); \ |
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32 | if (n) {skip_bits(gb, n);} |
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33 | |||
34 | /** |
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35 | * @brief read one block from stream |
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36 | * @param gb contains stream data |
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37 | * @param block where data is written to |
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38 | * @param scan array containing the mapping stream address -> block position |
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39 | * @param quant quantization factors |
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40 | * @return 0 means the block is not coded, < 0 means an error occurred. |
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41 | * |
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42 | * Note: GetBitContext is used to make the code simpler, since all data is |
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43 | * aligned this could be done faster in a different way, e.g. as it is done |
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44 | * in MPlayer libmpcodecs/native/rtjpegn.c. |
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45 | */ |
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46 | static inline int get_block(GetBitContext *gb, int16_t *block, const uint8_t *scan, |
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47 | const uint32_t *quant) { |
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48 | int coeff, i, n; |
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49 | int8_t ac; |
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50 | uint8_t dc = get_bits(gb, 8); |
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51 | |||
52 | // block not coded |
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53 | if (dc == 255) |
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54 | return 0; |
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55 | |||
56 | // number of non-zero coefficients |
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57 | coeff = get_bits(gb, 6); |
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58 | if (get_bits_left(gb) < (coeff << 1)) |
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59 | return AVERROR_INVALIDDATA; |
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60 | |||
61 | // normally we would only need to clear the (63 - coeff) last values, |
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62 | // but since we do not know where they are we just clear the whole block |
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63 | memset(block, 0, 64 * sizeof(int16_t)); |
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64 | |||
65 | // 2 bits per coefficient |
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66 | while (coeff) { |
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67 | ac = get_sbits(gb, 2); |
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68 | if (ac == -2) |
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69 | break; // continue with more bits |
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70 | PUT_COEFF(ac); |
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71 | } |
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72 | |||
73 | // 4 bits per coefficient |
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74 | ALIGN(4); |
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75 | if (get_bits_left(gb) < (coeff << 2)) |
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76 | return AVERROR_INVALIDDATA; |
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77 | while (coeff) { |
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78 | ac = get_sbits(gb, 4); |
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79 | if (ac == -8) |
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80 | break; // continue with more bits |
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81 | PUT_COEFF(ac); |
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82 | } |
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83 | |||
84 | // 8 bits per coefficient |
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85 | ALIGN(8); |
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86 | if (get_bits_left(gb) < (coeff << 3)) |
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87 | return AVERROR_INVALIDDATA; |
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88 | while (coeff) { |
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89 | ac = get_sbits(gb, 8); |
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90 | PUT_COEFF(ac); |
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91 | } |
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92 | |||
93 | PUT_COEFF(dc); |
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94 | return 1; |
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95 | } |
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96 | |||
97 | /** |
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98 | * @brief decode one rtjpeg YUV420 frame |
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99 | * @param c context, must be initialized via ff_rtjpeg_decode_init |
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100 | * @param f AVFrame to place decoded frame into. If parts of the frame |
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101 | * are not coded they are left unchanged, so consider initializing it |
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102 | * @param buf buffer containing input data |
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103 | * @param buf_size length of input data in bytes |
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104 | * @return number of bytes consumed from the input buffer |
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105 | */ |
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106 | int ff_rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f, |
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107 | const uint8_t *buf, int buf_size) { |
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108 | GetBitContext gb; |
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109 | int w = c->w / 16, h = c->h / 16; |
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110 | int x, y, ret; |
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111 | uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0]; |
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112 | uint8_t *u = f->data[1], *v = f->data[2]; |
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113 | |||
114 | if ((ret = init_get_bits8(&gb, buf, buf_size)) < 0) |
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115 | return ret; |
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116 | |||
117 | for (y = 0; y < h; y++) { |
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118 | for (x = 0; x < w; x++) { |
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119 | #define BLOCK(quant, dst, stride) do { \ |
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120 | int res = get_block(&gb, block, c->scan, quant); \ |
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121 | if (res < 0) \ |
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122 | return res; \ |
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123 | if (res > 0) \ |
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124 | c->dsp->idct_put(dst, stride, block); \ |
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125 | } while (0) |
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126 | int16_t *block = c->block; |
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127 | BLOCK(c->lquant, y1, f->linesize[0]); |
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128 | y1 += 8; |
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129 | BLOCK(c->lquant, y1, f->linesize[0]); |
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130 | y1 += 8; |
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131 | BLOCK(c->lquant, y2, f->linesize[0]); |
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132 | y2 += 8; |
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133 | BLOCK(c->lquant, y2, f->linesize[0]); |
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134 | y2 += 8; |
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135 | BLOCK(c->cquant, u, f->linesize[1]); |
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136 | u += 8; |
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137 | BLOCK(c->cquant, v, f->linesize[2]); |
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138 | v += 8; |
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139 | } |
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140 | y1 += 2 * 8 * (f->linesize[0] - w); |
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141 | y2 += 2 * 8 * (f->linesize[0] - w); |
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142 | u += 8 * (f->linesize[1] - w); |
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143 | v += 8 * (f->linesize[2] - w); |
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144 | } |
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145 | return get_bits_count(&gb) / 8; |
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146 | } |
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147 | |||
148 | /** |
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149 | * @brief initialize an RTJpegContext, may be called multiple times |
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150 | * @param c context to initialize |
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151 | * @param dsp specifies the idct to use for decoding |
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152 | * @param width width of image, will be rounded down to the nearest multiple |
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153 | * of 16 for decoding |
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154 | * @param height height of image, will be rounded down to the nearest multiple |
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155 | * of 16 for decoding |
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156 | * @param lquant luma quantization table to use |
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157 | * @param cquant chroma quantization table to use |
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158 | */ |
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159 | void ff_rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp, |
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160 | int width, int height, |
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161 | const uint32_t *lquant, const uint32_t *cquant) { |
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162 | int i; |
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163 | c->dsp = dsp; |
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164 | for (i = 0; i < 64; i++) { |
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165 | int z = ff_zigzag_direct[i]; |
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166 | int p = c->dsp->idct_permutation[i]; |
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167 | z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant |
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168 | |||
169 | // permute the scan and quantization tables for the chosen idct |
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170 | c->scan[i] = c->dsp->idct_permutation[z]; |
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171 | c->lquant[p] = lquant[i]; |
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172 | c->cquant[p] = cquant[i]; |
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173 | } |
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174 | c->w = width; |
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175 | c->h = height; |
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176 | }><>>>>>>><>>><>>><>>> |