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ffmpeg-4.2.2/libavcodec/arm/cabac.h 5.13 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef AVCODEC_ARM_CABAC_H
  #define AVCODEC_ARM_CABAC_H
  
  #include "config.h"
  #if HAVE_ARMV6T2_INLINE
  
  #include "libavutil/attributes.h"
  #include "libavutil/internal.h"
  #include "libavcodec/cabac.h"
  
  #define get_cabac_inline get_cabac_inline_arm
  static av_always_inline int get_cabac_inline_arm(CABACContext *c,
                                                   uint8_t *const state)
  {
      int bit;
      void *reg_b, *reg_c, *tmp;
  
      __asm__ volatile(
          "ldrb       %[bit]        , [%[state]]                  \n\t"
          "add        %[r_b]        , %[tables]   , %[lps_off]    \n\t"
          "mov        %[tmp]        , %[range]                    \n\t"
          "and        %[range]      , %[range]    , #0xC0         \n\t"
          "add        %[r_b]        , %[r_b]      , %[bit]        \n\t"
          "ldrb       %[range]      , [%[r_b], %[range], lsl #1]  \n\t"
          "add        %[r_b]        , %[tables]   , %[norm_off]   \n\t"
          "sub        %[r_c]        , %[tmp]      , %[range]      \n\t"
          "lsl        %[tmp]        , %[r_c]      , #17           \n\t"
          "cmp        %[tmp]        , %[low]                      \n\t"
          "it         gt                                          \n\t"
          "movgt      %[range]      , %[r_c]                      \n\t"
          "itt        cc                                          \n\t"
          "mvncc      %[bit]        , %[bit]                      \n\t"
          "subcc      %[low]        , %[low]      , %[tmp]        \n\t"
          "add        %[r_c]        , %[tables]   , %[mlps_off]   \n\t"
          "ldrb       %[tmp]        , [%[r_b], %[range]]          \n\t"
          "ldrb       %[r_b]        , [%[r_c], %[bit]]            \n\t"
          "lsl        %[low]        , %[low]      , %[tmp]        \n\t"
          "lsl        %[range]      , %[range]    , %[tmp]        \n\t"
          "uxth       %[r_c]        , %[low]                      \n\t"
          "strb       %[r_b]        , [%[state]]                  \n\t"
          "tst        %[r_c]        , %[r_c]                      \n\t"
          "bne        2f                                          \n\t"
          "ldr        %[r_c]        , [%[c], %[byte]]             \n\t"
  #if UNCHECKED_BITSTREAM_READER
          "ldrh       %[tmp]        , [%[r_c]]                    \n\t"
          "add        %[r_c]        , %[r_c]      , #2            \n\t"
          "str        %[r_c]        , [%[c], %[byte]]             \n\t"
  #else
          "ldr        %[r_b]        , [%[c], %[end]]              \n\t"
          "ldrh       %[tmp]        , [%[r_c]]                    \n\t"
          "cmp        %[r_c]        , %[r_b]                      \n\t"
          "itt        lt                                          \n\t"
          "addlt      %[r_c]        , %[r_c]      , #2            \n\t"
          "strlt      %[r_c]        , [%[c], %[byte]]             \n\t"
  #endif
          "sub        %[r_c]        , %[low]      , #1            \n\t"
          "add        %[r_b]        , %[tables]   , %[norm_off]   \n\t"
          "eor        %[r_c]        , %[low]      , %[r_c]        \n\t"
          "rev        %[tmp]        , %[tmp]                      \n\t"
          "lsr        %[r_c]        , %[r_c]      , #15           \n\t"
          "lsr        %[tmp]        , %[tmp]      , #15           \n\t"
          "ldrb       %[r_c]        , [%[r_b], %[r_c]]            \n\t"
          "movw       %[r_b]        , #0xFFFF                     \n\t"
          "sub        %[tmp]        , %[tmp]      , %[r_b]        \n\t"
          "rsb        %[r_c]        , %[r_c]      , #7            \n\t"
          "lsl        %[tmp]        , %[tmp]      , %[r_c]        \n\t"
          "add        %[low]        , %[low]      , %[tmp]        \n\t"
          "2:                                                     \n\t"
          :    [bit]"=&r"(bit),
               [low]"+&r"(c->low),
             [range]"+&r"(c->range),
               [r_b]"=&r"(reg_b),
               [r_c]"=&r"(reg_c),
               [tmp]"=&r"(tmp)
          :        [c]"r"(c),
               [state]"r"(state),
              [tables]"r"(ff_h264_cabac_tables),
                [byte]"M"(offsetof(CABACContext, bytestream)),
                 [end]"M"(offsetof(CABACContext, bytestream_end)),
            [norm_off]"I"(H264_NORM_SHIFT_OFFSET),
             [lps_off]"I"(H264_LPS_RANGE_OFFSET),
            [mlps_off]"I"(H264_MLPS_STATE_OFFSET + 128)
          : "memory", "cc"
          );
  
      return bit & 1;
  }
  #endif /* HAVE_ARMV6T2_INLINE */
  
  #endif /* AVCODEC_ARM_CABAC_H */