LCOV - code coverage report
Current view: top level - libavcodec - rangecoder.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 51 53 96.2 %
Date: 2017-12-16 21:16:39 Functions: 4 4 100.0 %

          Line data    Source code
       1             : /*
       2             :  * Range coder
       3             :  * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
       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             : 
      22             : /**
      23             :  * @file
      24             :  * Range coder.
      25             :  * based upon
      26             :  *    "Range encoding: an algorithm for removing redundancy from a digitised
      27             :  *                     message.
      28             :  *     G. N. N. Martin                  Presented in March 1979 to the Video &
      29             :  *                                      Data Recording Conference,
      30             :  *     IBM UK Scientific Center         held in Southampton July 24-27 1979."
      31             :  */
      32             : 
      33             : #include <string.h>
      34             : 
      35             : #include "libavutil/attributes.h"
      36             : #include "libavutil/avassert.h"
      37             : #include "libavutil/intreadwrite.h"
      38             : 
      39             : #include "avcodec.h"
      40             : #include "rangecoder.h"
      41             : 
      42       11150 : av_cold void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size)
      43             : {
      44       11150 :     c->bytestream_start  =
      45       11150 :     c->bytestream        = buf;
      46       11150 :     c->bytestream_end    = buf + buf_size;
      47       11150 :     c->low               = 0;
      48       11150 :     c->range             = 0xFF00;
      49       11150 :     c->outstanding_count = 0;
      50       11150 :     c->outstanding_byte  = -1;
      51       11150 : }
      52             : 
      53        5615 : av_cold void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf,
      54             :                                    int buf_size)
      55             : {
      56             :     /* cast to avoid compiler warning */
      57        5615 :     ff_init_range_encoder(c, (uint8_t *)buf, buf_size);
      58             : 
      59        5615 :     c->low         = AV_RB16(c->bytestream);
      60        5615 :     c->bytestream += 2;
      61        5615 :     c->overread    = 0;
      62        5615 :     if (c->low >= 0xFF00) {
      63           0 :         c->low = 0xFF00;
      64           0 :         c->bytestream_end = c->bytestream;
      65             :     }
      66        5615 : }
      67             : 
      68        3890 : void ff_build_rac_states(RangeCoder *c, int factor, int max_p)
      69             : {
      70        3890 :     const int64_t one = 1LL << 32;
      71             :     int64_t p;
      72             :     int last_p8, p8, i;
      73             : 
      74        3890 :     memset(c->zero_state, 0, sizeof(c->zero_state));
      75        3890 :     memset(c->one_state, 0, sizeof(c->one_state));
      76             : 
      77        3890 :     last_p8 = 0;
      78        3890 :     p       = one / 2;
      79      501810 :     for (i = 0; i < 128; i++) {
      80      497920 :         p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one
      81      497920 :         if (p8 <= last_p8)
      82      338430 :             p8 = last_p8 + 1;
      83      497920 :         if (last_p8 && last_p8 < 256 && p8 <= max_p)
      84      186712 :             c->one_state[last_p8] = p8;
      85             : 
      86      497920 :         p      += ((one - p) * factor + one / 2) >> 32;
      87      497920 :         last_p8 = p8;
      88             :     }
      89             : 
      90      941364 :     for (i = 256 - max_p; i <= max_p; i++) {
      91      937474 :         if (c->one_state[i])
      92      186712 :             continue;
      93             : 
      94      750762 :         p  = (i * one + 128) >> 8;
      95      750762 :         p += ((one - p) * factor + one / 2) >> 32;
      96      750762 :         p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one
      97      750762 :         if (p8 <= i)
      98        3889 :             p8 = i + 1;
      99      750762 :         if (p8 > max_p)
     100        3890 :             p8 = max_p;
     101      750762 :         c->one_state[i] = p8;
     102             :     }
     103             : 
     104      991950 :     for (i = 1; i < 255; i++)
     105      988060 :         c->zero_state[i] = 256 - c->one_state[256 - i];
     106        3890 : }
     107             : 
     108             : /* Return the number of bytes written. */
     109        5535 : int ff_rac_terminate(RangeCoder *c)
     110             : {
     111        5535 :     c->range = 0xFF;
     112        5535 :     c->low  += 0xFF;
     113        5535 :     renorm_encoder(c);
     114        5535 :     c->range = 0xFF;
     115        5535 :     renorm_encoder(c);
     116             : 
     117             :     av_assert1(c->low   == 0);
     118             :     av_assert1(c->range >= 0x100);
     119             : 
     120        5535 :     return c->bytestream - c->bytestream_start;
     121             : }

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