LCOV - code coverage report
Current view: top level - libavcodec - dirac_arith.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 48 50 96.0 %
Date: 2017-12-16 01:21:47 Functions: 5 5 100.0 %

          Line data    Source code
       1             : /*
       2             :  * Copyright (C) 2007 Marco Gerards <marco@gnu.org>
       3             :  * Copyright (C) 2009 David Conrad
       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             :  * Arithmetic decoder for Dirac
      25             :  * @author Marco Gerards <marco@gnu.org>
      26             :  */
      27             : 
      28             : #ifndef AVCODEC_DIRAC_ARITH_H
      29             : #define AVCODEC_DIRAC_ARITH_H
      30             : 
      31             : #include "libavutil/x86/asm.h"
      32             : #include "bytestream.h"
      33             : #include "get_bits.h"
      34             : 
      35             : enum dirac_arith_contexts {
      36             :     CTX_ZPZN_F1,
      37             :     CTX_ZPNN_F1,
      38             :     CTX_NPZN_F1,
      39             :     CTX_NPNN_F1,
      40             :     CTX_ZP_F2,
      41             :     CTX_ZP_F3,
      42             :     CTX_ZP_F4,
      43             :     CTX_ZP_F5,
      44             :     CTX_ZP_F6,
      45             :     CTX_NP_F2,
      46             :     CTX_NP_F3,
      47             :     CTX_NP_F4,
      48             :     CTX_NP_F5,
      49             :     CTX_NP_F6,
      50             :     CTX_COEFF_DATA,
      51             :     CTX_SIGN_NEG,
      52             :     CTX_SIGN_ZERO,
      53             :     CTX_SIGN_POS,
      54             :     CTX_ZERO_BLOCK,
      55             :     CTX_DELTA_Q_F,
      56             :     CTX_DELTA_Q_DATA,
      57             :     CTX_DELTA_Q_SIGN,
      58             : 
      59             :     DIRAC_CTX_COUNT
      60             : };
      61             : 
      62             : // Dirac resets the arith decoder between decoding various types of data,
      63             : // so many contexts are never used simultaneously. Thus, we can reduce
      64             : // the number of contexts needed by reusing them.
      65             : #define CTX_SB_F1        CTX_ZP_F5
      66             : #define CTX_SB_DATA      0
      67             : #define CTX_PMODE_REF1   0
      68             : #define CTX_PMODE_REF2   1
      69             : #define CTX_GLOBAL_BLOCK 2
      70             : #define CTX_MV_F1        CTX_ZP_F2
      71             : #define CTX_MV_DATA      0
      72             : #define CTX_DC_F1        CTX_ZP_F5
      73             : #define CTX_DC_DATA      0
      74             : 
      75             : typedef struct {
      76             :     unsigned low;
      77             :     uint16_t range;
      78             :     int16_t  counter;
      79             : 
      80             :     const uint8_t *bytestream;
      81             :     const uint8_t *bytestream_end;
      82             : 
      83             :     uint16_t contexts[DIRAC_CTX_COUNT];
      84             : } DiracArith;
      85             : 
      86             : extern const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT];
      87             : extern const uint16_t ff_dirac_prob[256];
      88             : extern int16_t ff_dirac_prob_branchless[256][2];
      89             : 
      90     1024041 : static inline void renorm(DiracArith *c)
      91             : {
      92             : #if HAVE_FAST_CLZ
      93     1024041 :     int shift = 14 - av_log2_16bit(c->range-1) + ((c->range-1)>>15);
      94             : 
      95     1024041 :     c->low    <<= shift;
      96     1024041 :     c->range  <<= shift;
      97     1024041 :     c->counter += shift;
      98             : #else
      99             :     while (c->range <= 0x4000) {
     100             :         c->low   <<= 1;
     101             :         c->range <<= 1;
     102             :         c->counter++;
     103             :     }
     104             : #endif
     105     1024041 : }
     106             : 
     107     1024041 : static inline void refill(DiracArith *c)
     108             : {
     109     1024041 :     int counter = c->counter;
     110             : 
     111     1024041 :     if (counter >= 0) {
     112       46510 :         int new = bytestream_get_be16(&c->bytestream);
     113             : 
     114             :         // the spec defines overread bits to be 1, and streams rely on this
     115       46510 :         if (c->bytestream > c->bytestream_end) {
     116         495 :             new |= 0xff;
     117         495 :             if (c->bytestream > c->bytestream_end+1)
     118          91 :                 new |= 0xff00;
     119             : 
     120         495 :             c->bytestream = c->bytestream_end;
     121             :         }
     122             : 
     123       46510 :         c->low += new << counter;
     124       46510 :         counter -= 16;
     125             :     }
     126     1024041 :     c->counter = counter;
     127     1024041 : }
     128             : 
     129     1024041 : static inline int dirac_get_arith_bit(DiracArith *c, int ctx)
     130             : {
     131     1024041 :     int prob_zero = c->contexts[ctx];
     132             :     int range_times_prob, bit;
     133     1024041 :     unsigned low = c->low;
     134     1024041 :     int    range = c->range;
     135             : 
     136     1024041 :     range_times_prob = (c->range * prob_zero) >> 16;
     137             : 
     138             : #if ARCH_X86 && HAVE_FAST_CMOV && HAVE_INLINE_ASM && HAVE_6REGS
     139     1024041 :     low   -= range_times_prob << 16;
     140     1024041 :     range -= range_times_prob;
     141     1024041 :     bit = 0;
     142     1024041 :     __asm__(
     143             :         "cmpl   %5, %4 \n\t"
     144             :         "setae  %b0    \n\t"
     145             :         "cmovb  %3, %2 \n\t"
     146             :         "cmovb  %5, %1 \n\t"
     147             :         : "+q"(bit), "+r"(range), "+r"(low)
     148     1024041 :         : "r"(c->low), "r"(c->low>>16),
     149             :           "r"(range_times_prob)
     150             :     );
     151             : #else
     152             :     bit = (low >> 16) >= range_times_prob;
     153             :     if (bit) {
     154             :         low   -= range_times_prob << 16;
     155             :         range -= range_times_prob;
     156             :     } else {
     157             :         range  = range_times_prob;
     158             :     }
     159             : #endif
     160             : 
     161     1024041 :     c->contexts[ctx] += ff_dirac_prob_branchless[prob_zero>>8][bit];
     162     1024041 :     c->low   = low;
     163     1024041 :     c->range = range;
     164             : 
     165     1024041 :     renorm(c);
     166     1024041 :     refill(c);
     167     1024041 :     return bit;
     168             : }
     169             : 
     170      353584 : static inline int dirac_get_arith_uint(DiracArith *c, int follow_ctx, int data_ctx)
     171             : {
     172      353584 :     int ret = 1;
     173      927090 :     while (!dirac_get_arith_bit(c, follow_ctx)) {
     174      219922 :         if (ret >= 0x40000000) {
     175           0 :             av_log(NULL, AV_LOG_ERROR, "dirac_get_arith_uint overflow\n");
     176           0 :             return -1;
     177             :         }
     178      219922 :         ret <<= 1;
     179      219922 :         ret += dirac_get_arith_bit(c, data_ctx);
     180      219922 :         follow_ctx = ff_dirac_next_ctx[follow_ctx];
     181             :     }
     182      353584 :     return ret-1;
     183             : }
     184             : 
     185       14164 : static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ctx)
     186             : {
     187       14164 :     int ret = dirac_get_arith_uint(c, follow_ctx, data_ctx);
     188       14164 :     if (ret && dirac_get_arith_bit(c, data_ctx+1))
     189        1346 :         ret = -ret;
     190       14164 :     return ret;
     191             : }
     192             : 
     193             : void ff_dirac_init_arith_tables(void);
     194             : void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length);
     195             : 
     196             : #endif /* AVCODEC_DIRAC_ARITH_H */

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