• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • File List
  • Globals

libavcodec/rtjpeg.c

Go to the documentation of this file.
00001 /*
00002  * RTJpeg decoding functions
00003  * Copyright (c) 2006 Reimar Doeffinger
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 #include "libavutil/common.h"
00022 #include "get_bits.h"
00023 #include "dsputil.h"
00024 #include "rtjpeg.h"
00025 
00026 #define PUT_COEFF(c) \
00027     i = scan[coeff--]; \
00028     block[i] = (c) * quant[i];
00029 
00031 #define ALIGN(a) \
00032     n = (-get_bits_count(gb)) & (a - 1); \
00033     if (n) {skip_bits(gb, n);}
00034 
00047 static inline int get_block(GetBitContext *gb, DCTELEM *block, const uint8_t *scan,
00048                             const uint32_t *quant) {
00049     int coeff, i, n;
00050     int8_t ac;
00051     uint8_t dc = get_bits(gb, 8);
00052 
00053     // block not coded
00054     if (dc == 255)
00055        return 0;
00056 
00057     // number of non-zero coefficients
00058     coeff = get_bits(gb, 6);
00059     if (get_bits_count(gb) + (coeff << 1) >= gb->size_in_bits)
00060         return -1;
00061 
00062     // normally we would only need to clear the (63 - coeff) last values,
00063     // but since we do not know where they are we just clear the whole block
00064     memset(block, 0, 64 * sizeof(DCTELEM));
00065 
00066     // 2 bits per coefficient
00067     while (coeff) {
00068         ac = get_sbits(gb, 2);
00069         if (ac == -2)
00070             break; // continue with more bits
00071         PUT_COEFF(ac);
00072     }
00073 
00074     // 4 bits per coefficient
00075     ALIGN(4);
00076     if (get_bits_count(gb) + (coeff << 2) >= gb->size_in_bits)
00077         return -1;
00078     while (coeff) {
00079         ac = get_sbits(gb, 4);
00080         if (ac == -8)
00081             break; // continue with more bits
00082         PUT_COEFF(ac);
00083     }
00084 
00085     // 8 bits per coefficient
00086     ALIGN(8);
00087     if (get_bits_count(gb) + (coeff << 3) >= gb->size_in_bits)
00088         return -1;
00089     while (coeff) {
00090         ac = get_sbits(gb, 8);
00091         PUT_COEFF(ac);
00092     }
00093 
00094     PUT_COEFF(dc);
00095     return 1;
00096 }
00097 
00107 int rtjpeg_decode_frame_yuv420(RTJpegContext *c, AVFrame *f,
00108                                const uint8_t *buf, int buf_size) {
00109     GetBitContext gb;
00110     int w = c->w / 16, h = c->h / 16;
00111     int x, y;
00112     uint8_t *y1 = f->data[0], *y2 = f->data[0] + 8 * f->linesize[0];
00113     uint8_t *u = f->data[1], *v = f->data[2];
00114     init_get_bits(&gb, buf, buf_size * 8);
00115     for (y = 0; y < h; y++) {
00116         for (x = 0; x < w; x++) {
00117             DCTELEM *block = c->block;
00118             if (get_block(&gb, block, c->scan, c->lquant) > 0)
00119                 c->dsp->idct_put(y1, f->linesize[0], block);
00120             y1 += 8;
00121             if (get_block(&gb, block, c->scan, c->lquant) > 0)
00122                 c->dsp->idct_put(y1, f->linesize[0], block);
00123             y1 += 8;
00124             if (get_block(&gb, block, c->scan, c->lquant) > 0)
00125                 c->dsp->idct_put(y2, f->linesize[0], block);
00126             y2 += 8;
00127             if (get_block(&gb, block, c->scan, c->lquant) > 0)
00128                 c->dsp->idct_put(y2, f->linesize[0], block);
00129             y2 += 8;
00130             if (get_block(&gb, block, c->scan, c->cquant) > 0)
00131                 c->dsp->idct_put(u, f->linesize[1], block);
00132             u += 8;
00133             if (get_block(&gb, block, c->scan, c->cquant) > 0)
00134                 c->dsp->idct_put(v, f->linesize[2], block);
00135             v += 8;
00136         }
00137         y1 += 2 * 8 * (f->linesize[0] - w);
00138         y2 += 2 * 8 * (f->linesize[0] - w);
00139         u += 8 * (f->linesize[1] - w);
00140         v += 8 * (f->linesize[2] - w);
00141     }
00142     return get_bits_count(&gb) / 8;
00143 }
00144 
00156 void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
00157                         int width, int height,
00158                         const uint32_t *lquant, const uint32_t *cquant) {
00159     int i;
00160     c->dsp = dsp;
00161     for (i = 0; i < 64; i++) {
00162         int z = ff_zigzag_direct[i];
00163         int p = c->dsp->idct_permutation[i];
00164         z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant
00165 
00166         // permute the scan and quantization tables for the chosen idct
00167         c->scan[i] = c->dsp->idct_permutation[z];
00168         c->lquant[p] = lquant[i];
00169         c->cquant[p] = cquant[i];
00170     }
00171     c->w = width;
00172     c->h = height;
00173 }

Generated on Fri Sep 16 2011 17:17:42 for FFmpeg by  doxygen 1.7.1