1/*
2 * RTJpeg decoding functions
3 * Copyright (c) 2006 Reimar Doeffinger
4 *
5 * This file is part of Libav.
6 *
7 * Libav 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 * Libav 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 Libav; 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 given 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_left(gb) < (coeff << 1))
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_left(gb) < (coeff << 2))
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_left(gb) < (coeff << 3))
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#define BLOCK(quant, dst, stride) do { \
118    int res = get_block(&gb, block, c->scan, quant); \
119    if (res < 0) \
120        return res; \
121    if (res > 0) \
122        c->dsp->idct_put(dst, stride, block); \
123} while (0)
124            DCTELEM *block = c->block;
125            BLOCK(c->lquant, y1, f->linesize[0]);
126            y1 += 8;
127            BLOCK(c->lquant, y1, f->linesize[0]);
128            y1 += 8;
129            BLOCK(c->lquant, y2, f->linesize[0]);
130            y2 += 8;
131            BLOCK(c->lquant, y2, f->linesize[0]);
132            y2 += 8;
133            BLOCK(c->cquant, u,  f->linesize[1]);
134            u += 8;
135            BLOCK(c->cquant, v,  f->linesize[2]);
136            v += 8;
137        }
138        y1 += 2 * 8 * (f->linesize[0] - w);
139        y2 += 2 * 8 * (f->linesize[0] - w);
140        u += 8 * (f->linesize[1] - w);
141        v += 8 * (f->linesize[2] - w);
142    }
143    return get_bits_count(&gb) / 8;
144}
145
146/**
147 * @brief initialize an RTJpegContext, may be called multiple times
148 * @param c context to initialize
149 * @param dsp specifies the idct to use for decoding
150 * @param width width of image, will be rounded down to the nearest multiple
151 *              of 16 for decoding
152 * @param height height of image, will be rounded down to the nearest multiple
153 *              of 16 for decoding
154 * @param lquant luma quantization table to use
155 * @param cquant chroma quantization table to use
156 */
157void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
158                        int width, int height,
159                        const uint32_t *lquant, const uint32_t *cquant) {
160    int i;
161    c->dsp = dsp;
162    for (i = 0; i < 64; i++) {
163        int z = ff_zigzag_direct[i];
164        int p = c->dsp->idct_permutation[i];
165        z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
166
167        // permute the scan and quantization tables for the chosen idct
168        c->scan[i] = c->dsp->idct_permutation[z];
169        c->lquant[p] = lquant[i];
170        c->cquant[p] = cquant[i];
171    }
172    c->w = width;
173    c->h = height;
174}
175