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 "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  */
  46 static 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  */
  99 int 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  */
 148 void 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 }