vpx/vp9/common/vp9_scale.c

/*
 *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "./vp9_rtcd.h"
#include "vp9/common/vp9_scale.h"

static int scaled_x(int val, const struct scale_factors *scale) {
  return val * scale->x_scale_fp >> VP9_REF_SCALE_SHIFT;
}

static int scaled_y(int val, const struct scale_factors *scale) {
  return val * scale->y_scale_fp >> VP9_REF_SCALE_SHIFT;
}

static int unscaled_value(int val, const struct scale_factors *scale) {
  (void) scale;
  return val;
}

static MV32 scaled_mv(const MV *mv, const struct scale_factors *scale) {
  const MV32 res = {
    (mv->row * scale->y_scale_fp >> VP9_REF_SCALE_SHIFT) + scale->y_offset_q4,
    (mv->col * scale->x_scale_fp >> VP9_REF_SCALE_SHIFT) + scale->x_offset_q4
  };
  return res;
}

static MV32 unscaled_mv(const MV *mv, const struct scale_factors *scale) {
  const MV32 res = {
    mv->row,
    mv->col
  };
  return res;
}

static void set_offsets_with_scaling(struct scale_factors *scale,
                                     int row, int col) {
  const int x_q4 = 16 * col;
  const int y_q4 = 16 * row;

  scale->x_offset_q4 = (x_q4 * scale->x_scale_fp >> VP9_REF_SCALE_SHIFT) & 0xF;
  scale->y_offset_q4 = (y_q4 * scale->y_scale_fp >> VP9_REF_SCALE_SHIFT) & 0xF;
}

static void set_offsets_without_scaling(struct scale_factors *scale,
                                        int row, int col) {
  scale->x_offset_q4 = 0;
  scale->y_offset_q4 = 0;
}

static int get_fixed_point_scale_factor(int other_size, int this_size) {
  // Calculate scaling factor once for each reference frame
  // and use fixed point scaling factors in decoding and encoding routines.
  // Hardware implementations can calculate scale factor in device driver
  // and use multiplication and shifting on hardware instead of division.
  return (other_size << VP9_REF_SCALE_SHIFT) / this_size;
}

void vp9_setup_scale_factors_for_frame(struct scale_factors *scale,
                                       int other_w, int other_h,
                                       int this_w, int this_h) {
  scale->x_scale_fp = get_fixed_point_scale_factor(other_w, this_w);
  scale->x_offset_q4 = 0;  // calculated per-mb
  scale->x_step_q4 = (16 * scale->x_scale_fp >> VP9_REF_SCALE_SHIFT);

  scale->y_scale_fp = get_fixed_point_scale_factor(other_h, this_h);
  scale->y_offset_q4 = 0;  // calculated per-mb
  scale->y_step_q4 = (16 * scale->y_scale_fp >> VP9_REF_SCALE_SHIFT);

  if (other_w == this_w && other_h == this_h) {
    scale->scale_value_x = unscaled_value;
    scale->scale_value_y = unscaled_value;
    scale->set_scaled_offsets = set_offsets_without_scaling;
    scale->scale_mv = unscaled_mv;
  } else {
    scale->scale_value_x = scaled_x;
    scale->scale_value_y = scaled_y;
    scale->set_scaled_offsets = set_offsets_with_scaling;
    scale->scale_mv = scaled_mv;
  }

  // TODO(agrange): Investigate the best choice of functions to use here
  // for EIGHTTAP_SMOOTH. Since it is not interpolating, need to choose what
  // to do at full-pel offsets. The current selection, where the filter is
  // applied in one direction only, and not at all for 0,0, seems to give the
  // best quality, but it may be worth trying an additional mode that does
  // do the filtering on full-pel.
  if (scale->x_step_q4 == 16) {
    if (scale->y_step_q4 == 16) {
      // No scaling in either direction.
      scale->predict[0][0][0] = vp9_convolve_copy;
      scale->predict[0][0][1] = vp9_convolve_avg;
      scale->predict[0][1][0] = vp9_convolve8_vert;
      scale->predict[0][1][1] = vp9_convolve8_avg_vert;
      scale->predict[1][0][0] = vp9_convolve8_horiz;
      scale->predict[1][0][1] = vp9_convolve8_avg_horiz;
    } else {
      // No scaling in x direction. Must always scale in the y direction.
      scale->predict[0][0][0] = vp9_convolve8_vert;
      scale->predict[0][0][1] = vp9_convolve8_avg_vert;
      scale->predict[0][1][0] = vp9_convolve8_vert;
      scale->predict[0][1][1] = vp9_convolve8_avg_vert;
      scale->predict[1][0][0] = vp9_convolve8;
      scale->predict[1][0][1] = vp9_convolve8_avg;
    }
  } else {
    if (scale->y_step_q4 == 16) {
      // No scaling in the y direction. Must always scale in the x direction.
      scale->predict[0][0][0] = vp9_convolve8_horiz;
      scale->predict[0][0][1] = vp9_convolve8_avg_horiz;
      scale->predict[0][1][0] = vp9_convolve8;
      scale->predict[0][1][1] = vp9_convolve8_avg;
      scale->predict[1][0][0] = vp9_convolve8_horiz;
      scale->predict[1][0][1] = vp9_convolve8_avg_horiz;
    } else {
      // Must always scale in both directions.
      scale->predict[0][0][0] = vp9_convolve8;
      scale->predict[0][0][1] = vp9_convolve8_avg;
      scale->predict[0][1][0] = vp9_convolve8;
      scale->predict[0][1][1] = vp9_convolve8_avg;
      scale->predict[1][0][0] = vp9_convolve8;
      scale->predict[1][0][1] = vp9_convolve8_avg;
    }
  }
  // 2D subpel motion always gets filtered in both directions
  scale->predict[1][1][0] = vp9_convolve8;
  scale->predict[1][1][1] = vp9_convolve8_avg;
}