text: /*
   * This file is part of the Independent JPEG Group's software.
   *
   * The authors make NO WARRANTY or representation, either express or implied,
   * with respect to this software, its quality, accuracy, merchantability, or
   * fitness for a particular purpose.  This software is provided "AS IS", and
   * you, its user, assume the entire risk as to its quality and accuracy.
   *
   * This software is copyright (C) 1994-1996, Thomas G. Lane.
   * All Rights Reserved except as specified below.
   *
   * Permission is hereby granted to use, copy, modify, and distribute this
   * software (or portions thereof) for any purpose, without fee, subject to
   * these conditions:
   * (1) If any part of the source code for this software is distributed, then
   * this README file must be included, with this copyright and no-warranty
   * notice unaltered; and any additions, deletions, or changes to the original
   * files must be clearly indicated in accompanying documentation.
   * (2) If only executable code is distributed, then the accompanying
   * documentation must state that "this software is based in part on the work
   * of the Independent JPEG Group".
   * (3) Permission for use of this software is granted only if the user accepts
   * full responsibility for any undesirable consequences; the authors accept
   * NO LIABILITY for damages of any kind.
   *
   * These conditions apply to any software derived from or based on the IJG
   * code, not just to the unmodified library.  If you use our work, you ought
   * to acknowledge us.
   *
   * Permission is NOT granted for the use of any IJG author's name or company
   * name in advertising or publicity relating to this software or products
   * derived from it.  This software may be referred to only as "the Independent
   * JPEG Group's software".
   *
   * We specifically permit and encourage the use of this software as the basis
   * of commercial products, provided that all warranty or liability claims are
   * assumed by the product vendor.
   *
   * This file contains a fast, not so accurate integer implementation of the
   * forward DCT (Discrete Cosine Transform).
   *
   * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
   * on each column.  Direct algorithms are also available, but they are
   * much more complex and seem not to be any faster when reduced to code.
   *
   * This implementation is based on Arai, Agui, and Nakajima's algorithm for
   * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
   * Japanese, but the algorithm is described in the Pennebaker & Mitchell
   * JPEG textbook (see REFERENCES section in file README).  The following code
   * is based directly on figure 4-8 in P&M.
   * While an 8-point DCT cannot be done in less than 11 multiplies, it is
   * possible to arrange the computation so that many of the multiplies are
   * simple scalings of the final outputs.  These multiplies can then be
   * folded into the multiplications or divisions by the JPEG quantization
   * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
   * to be done in the DCT itself.
   * The primary disadvantage of this method is that with fixed-point math,
   * accuracy is lost due to imprecise representation of the scaled
   * quantization values.  The smaller the quantization table entry, the less
   * precise the scaled value, so this implementation does worse with high-
   * quality-setting files than with low-quality ones.
   */
  
  /**
   * @file
   * Independent JPEG Group's fast AAN dct.
   */
  
  #include <stdlib.h>
  #include <stdio.h>
  #include "libavutil/common.h"
  #include "dct.h"
  
  #define DCTSIZE 8
  #define GLOBAL(x) x
  #define RIGHT_SHIFT(x, n) ((x) >> (n))
  
  /*
   * This module is specialized to the case DCTSIZE = 8.
   */
  
  #if DCTSIZE != 8
    Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
  #endif
  
  
  /* Scaling decisions are generally the same as in the LL&M algorithm;
   * see jfdctint.c for more details.  However, we choose to descale
   * (right shift) multiplication products as soon as they are formed,
   * rather than carrying additional fractional bits into subsequent additions.
   * This compromises accuracy slightly, but it lets us save a few shifts.
   * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
   * everywhere except in the multiplications proper; this saves a good deal
   * of work on 16-bit-int machines.
   *
   * Again to save a few shifts, the intermediate results between pass 1 and
   * pass 2 are not upscaled, but are represented only to integral precision.
   *
   * A final compromise is to represent the multiplicative constants to only
   * 8 fractional bits, rather than 13.  This saves some shifting work on some
   * machines, and may also reduce the cost of multiplication (since there
   * are fewer one-bits in the constants).
   */
  
  #define CONST_BITS  8
  
  
  /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
   * causing a lot of useless floating-point operations at run time.
   * To get around this we use the following pre-calculated constants.
   * If you change CONST_BITS you may want to add appropriate values.
   * (With a reasonable C compiler, you can just rely on the FIX() macro...)
   */
  
  #if CONST_BITS == 8
  #define FIX_0_382683433  ((int32_t)   98)       /* FIX(0.382683433) */
  #define FIX_0_541196100  ((int32_t)  139)       /* FIX(0.541196100) */
  #define FIX_0_707106781  ((int32_t)  181)       /* FIX(0.707106781) */
  #define FIX_1_306562965  ((int32_t)  334)       /* FIX(1.306562965) */
  #else
  #define FIX_0_382683433  FIX(0.382683433)
  #define FIX_0_541196100  FIX(0.541196100)
  #define FIX_0_707106781  FIX(0.707106781)
  #define FIX_1_306562965  FIX(1.306562965)
  #endif
  
  
  /* We can gain a little more speed, with a further compromise in accuracy,
   * by omitting the addition in a descaling shift.  This yields an incorrectly
   * rounded result half the time...
   */
  
  #ifndef USE_ACCURATE_ROUNDING
  #undef DESCALE
  #define DESCALE(x,n)  RIGHT_SHIFT(x, n)
  #endif
  
  
  /* Multiply a int16_t variable by an int32_t constant, and immediately
   * descale to yield a int16_t result.
   */
  
  #define MULTIPLY(var,const)  ((int16_t) DESCALE((var) * (const), CONST_BITS))
  
  static av_always_inline void row_fdct(int16_t * data){
    int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
    int tmp10, tmp11, tmp12, tmp13;
    int z1, z2, z3, z4, z5, z11, z13;
    int16_t *dataptr;
    int ctr;
  
    /* Pass 1: process rows. */
  
    dataptr = data;
    for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
      tmp0 = dataptr[0] + dataptr[7];
      tmp7 = dataptr[0] - dataptr[7];
      tmp1 = dataptr[1] + dataptr[6];
      tmp6 = dataptr[1] - dataptr[6];
      tmp2 = dataptr[2] + dataptr[5];
      tmp5 = dataptr[2] - dataptr[5];
      tmp3 = dataptr[3] + dataptr[4];
      tmp4 = dataptr[3] - dataptr[4];
  
      /* Even part */
  
      tmp10 = tmp0 + tmp3;        /* phase 2 */
      tmp13 = tmp0 - tmp3;
      tmp11 = tmp1 + tmp2;
      tmp12 = tmp1 - tmp2;
  
      dataptr[0] = tmp10 + tmp11; /* phase 3 */
      dataptr[4] = tmp10 - tmp11;
  
      z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
      dataptr[2] = tmp13 + z1;    /* phase 5 */
      dataptr[6] = tmp13 - z1;
  
      /* Odd part */
  
      tmp10 = tmp4 + tmp5;        /* phase 2 */
      tmp11 = tmp5 + tmp6;
      tmp12 = tmp6 + tmp7;
  
      /* The rotator is modified from fig 4-8 to avoid extra negations. */
      z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
      z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5;    /* c2-c6 */
      z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5;    /* c2+c6 */
      z3 = MULTIPLY(tmp11, FIX_0_707106781);         /* c4 */
  
      z11 = tmp7 + z3;            /* phase 5 */
      z13 = tmp7 - z3;
  
      dataptr[5] = z13 + z2;      /* phase 6 */
      dataptr[3] = z13 - z2;
      dataptr[1] = z11 + z4;
      dataptr[7] = z11 - z4;
  
      dataptr += DCTSIZE;         /* advance pointer to next row */
    }
  }
  
  /*
   * Perform the forward DCT on one block of samples.
   */
  
  GLOBAL(void)
  ff_fdct_ifast (int16_t * data)
  {
    int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
    int tmp10, tmp11, tmp12, tmp13;
    int z1, z2, z3, z4, z5, z11, z13;
    int16_t *dataptr;
    int ctr;
  
    row_fdct(data);
  
    /* Pass 2: process columns. */
  
    dataptr = data;
    for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
      tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
      tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
      tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
      tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
      tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
      tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
      tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
      tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
  
      /* Even part */
  
      tmp10 = tmp0 + tmp3;        /* phase 2 */
      tmp13 = tmp0 - tmp3;
      tmp11 = tmp1 + tmp2;
      tmp12 = tmp1 - tmp2;
  
      dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
      dataptr[DCTSIZE*4] = tmp10 - tmp11;
  
      z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
      dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
      dataptr[DCTSIZE*6] = tmp13 - z1;
  
      /* Odd part */
  
      tmp10 = tmp4 + tmp5;        /* phase 2 */
      tmp11 = tmp5 + tmp6;
      tmp12 = tmp6 + tmp7;
  
      /* The rotator is modified from fig 4-8 to avoid extra negations. */
      z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
      z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
      z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
      z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */
  
      z11 = tmp7 + z3;            /* phase 5 */
      z13 = tmp7 - z3;
  
      dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
      dataptr[DCTSIZE*3] = z13 - z2;
      dataptr[DCTSIZE*1] = z11 + z4;
      dataptr[DCTSIZE*7] = z11 - z4;
  
      dataptr++;                  /* advance pointer to next column */
    }
  }
  
  /*
   * Perform the forward 2-4-8 DCT on one block of samples.
   */
  
  GLOBAL(void)
  ff_fdct_ifast248 (int16_t * data)
  {
    int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
    int tmp10, tmp11, tmp12, tmp13;
    int z1;
    int16_t *dataptr;
    int ctr;
  
    row_fdct(data);
  
    /* Pass 2: process columns. */
  
    dataptr = data;
    for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
      tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1];
      tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3];
      tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5];
      tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7];
      tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1];
      tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3];
      tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5];
      tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7];
  
      /* Even part */
  
      tmp10 = tmp0 + tmp3;
      tmp11 = tmp1 + tmp2;
      tmp12 = tmp1 - tmp2;
      tmp13 = tmp0 - tmp3;
  
      dataptr[DCTSIZE*0] = tmp10 + tmp11;
      dataptr[DCTSIZE*4] = tmp10 - tmp11;
  
      z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781);
      dataptr[DCTSIZE*2] = tmp13 + z1;
      dataptr[DCTSIZE*6] = tmp13 - z1;
  
      tmp10 = tmp4 + tmp7;
      tmp11 = tmp5 + tmp6;
      tmp12 = tmp5 - tmp6;
      tmp13 = tmp4 - tmp7;
  
      dataptr[DCTSIZE*1] = tmp10 + tmp11;
      dataptr[DCTSIZE*5] = tmp10 - tmp11;
  
      z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781);
      dataptr[DCTSIZE*3] = tmp13 + z1;
      dataptr[DCTSIZE*7] = tmp13 - z1;
  
      dataptr++;                        /* advance pointer to next column */
    }
  }
  
  
  #undef GLOBAL
  #undef CONST_BITS
  #undef DESCALE
  #undef FIX_0_541196100
  #undef FIX_1_306562965
  