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/libavcodec/rtjpeg.c

http://github.com/FFmpeg/FFmpeg
C | 183 lines | 105 code | 18 blank | 60 comment | 21 complexity | 54948b331f336f238ae225bf3aaaa009 MD5 | raw file
  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 */
 46static 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 */
106int 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 */
158void 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
170void 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}