ffmpeg/libavcodec/rtjpeg.c

   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 }