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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 | } |