text: /*
   * AC-3 DSP utils
   * Copyright (c) 2011 Justin Ruggles
   *
   * This file is part of Libav.
   *
   * Libav 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.
   *
   * Libav 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 Libav; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "libavutil/avassert.h"
  #include "avcodec.h"
  #include "ac3.h"
  #include "ac3dsp.h"
  
  static void ac3_exponent_min_c(uint8_t *exp, int num_reuse_blocks, int nb_coefs)
  {
      int blk, i;
  
      if (!num_reuse_blocks)
          return;
  
      for (i = 0; i < nb_coefs; i++) {
          uint8_t min_exp = *exp;
          uint8_t *exp1 = exp + 256;
          for (blk = 0; blk < num_reuse_blocks; blk++) {
              uint8_t next_exp = *exp1;
              if (next_exp < min_exp)
                  min_exp = next_exp;
              exp1 += 256;
          }
          *exp++ = min_exp;
      }
  }
  
  static int ac3_max_msb_abs_int16_c(const int16_t *src, int len)
  {
      int i, v = 0;
      for (i = 0; i < len; i++)
          v |= abs(src[i]);
      return v;
  }
  
  static void ac3_lshift_int16_c(int16_t *src, unsigned int len,
                                 unsigned int shift)
  {
      uint32_t *src32 = (uint32_t *)src;
      const uint32_t mask = ~(((1 << shift) - 1) << 16);
      int i;
      len >>= 1;
      for (i = 0; i < len; i += 8) {
          src32[i  ] = (src32[i  ] << shift) & mask;
          src32[i+1] = (src32[i+1] << shift) & mask;
          src32[i+2] = (src32[i+2] << shift) & mask;
          src32[i+3] = (src32[i+3] << shift) & mask;
          src32[i+4] = (src32[i+4] << shift) & mask;
          src32[i+5] = (src32[i+5] << shift) & mask;
          src32[i+6] = (src32[i+6] << shift) & mask;
          src32[i+7] = (src32[i+7] << shift) & mask;
      }
  }
  
  static void ac3_rshift_int32_c(int32_t *src, unsigned int len,
                                 unsigned int shift)
  {
      do {
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          *src++ >>= shift;
          len -= 8;
      } while (len > 0);
  }
  
  static void float_to_fixed24_c(int32_t *dst, const float *src, unsigned int len)
  {
      const float scale = 1 << 24;
      do {
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          *dst++ = lrintf(*src++ * scale);
          len -= 8;
      } while (len > 0);
  }
  
  static void ac3_bit_alloc_calc_bap_c(int16_t *mask, int16_t *psd,
                                       int start, int end,
                                       int snr_offset, int floor,
                                       const uint8_t *bap_tab, uint8_t *bap)
  {
      int bin, band, band_end;
  
      /* special case, if snr offset is -960, set all bap's to zero */
      if (snr_offset == -960) {
          memset(bap, 0, AC3_MAX_COEFS);
          return;
      }
  
      bin  = start;
      band = ff_ac3_bin_to_band_tab[start];
      do {
          int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor;
          band_end = ff_ac3_band_start_tab[++band];
          band_end = FFMIN(band_end, end);
  
          for (; bin < band_end; bin++) {
              int address = av_clip((psd[bin] - m) >> 5, 0, 63);
              bap[bin] = bap_tab[address];
          }
      } while (end > band_end);
  }
  
  static void ac3_update_bap_counts_c(uint16_t mant_cnt[16], uint8_t *bap,
                                      int len)
  {
      while (len-- > 0)
          mant_cnt[bap[len]]++;
  }
  
  DECLARE_ALIGNED(16, const uint16_t, ff_ac3_bap_bits)[16] = {
      0,  0,  0,  3,  0,  4,  5,  6,  7,  8,  9, 10, 11, 12, 14, 16
  };
  
  static int ac3_compute_mantissa_size_c(uint16_t mant_cnt[6][16])
  {
      int blk, bap;
      int bits = 0;
  
      for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
          // bap=1 : 3 mantissas in 5 bits
          bits += (mant_cnt[blk][1] / 3) * 5;
          // bap=2 : 3 mantissas in 7 bits
          // bap=4 : 2 mantissas in 7 bits
          bits += ((mant_cnt[blk][2] / 3) + (mant_cnt[blk][4] >> 1)) * 7;
          // bap=3 : 1 mantissa in 3 bits
          bits += mant_cnt[blk][3] * 3;
          // bap=5 to 15 : get bits per mantissa from table
          for (bap = 5; bap < 16; bap++)
              bits += mant_cnt[blk][bap] * ff_ac3_bap_bits[bap];
      }
      return bits;
  }
  
  static void ac3_extract_exponents_c(uint8_t *exp, int32_t *coef, int nb_coefs)
  {
      int i;
  
      for (i = 0; i < nb_coefs; i++) {
          int v = abs(coef[i]);
          exp[i] = v ? 23 - av_log2(v) : 24;
      }
  }
  
  av_cold void ff_ac3dsp_init(AC3DSPContext *c, int bit_exact)
  {
      c->ac3_exponent_min = ac3_exponent_min_c;
      c->ac3_max_msb_abs_int16 = ac3_max_msb_abs_int16_c;
      c->ac3_lshift_int16 = ac3_lshift_int16_c;
      c->ac3_rshift_int32 = ac3_rshift_int32_c;
      c->float_to_fixed24 = float_to_fixed24_c;
      c->bit_alloc_calc_bap = ac3_bit_alloc_calc_bap_c;
      c->update_bap_counts = ac3_update_bap_counts_c;
      c->compute_mantissa_size = ac3_compute_mantissa_size_c;
      c->extract_exponents = ac3_extract_exponents_c;
  
      if (ARCH_ARM)
          ff_ac3dsp_init_arm(c, bit_exact);
      if (HAVE_MMX)
          ff_ac3dsp_init_x86(c, bit_exact);
  }
  