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