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godot/thirdparty/astcenc/astcenc_pick_best_endpoint_format.cpp
Peter Harris 75ce42d463 Update astcenc to the upstream 5.3.0 release 
This is mostly a maintenance update that brings the compressor inline
with the recently published Khronos Data Format Specification 1.4
release which clarified some ambiguity in the specification. This update
also gives minor codec optimizations, bug fixes, and image quality
improvements.

The biggest improvement for Godot is that builds using MSVC cl.exe will
now correctly default to the SSE2-optimized backend rather than the
reference C backend. This makes compression more than 3 times faster.
Builds using other compilers (GCC, LLVM/Clang) were not impacted by the
underlying issue, and see no performance uplift.
2025-03-21 16:02:50 -07:00

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// SPDX-License-Identifier: Apache-2.0
// ----------------------------------------------------------------------------
// Copyright 2011-2025 Arm Limited
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// ----------------------------------------------------------------------------
#if !defined(ASTCENC_DECOMPRESS_ONLY)
/**
* @brief Functions for finding best endpoint format.
*
* We assume there are two independent sources of error in any given partition:
*
* - Encoding choice errors
* - Quantization errors
*
* Encoding choice errors are caused by encoder decisions. For example:
*
* - Using luminance instead of separate RGB components.
* - Using a constant 1.0 alpha instead of storing an alpha component.
* - Using RGB+scale instead of storing two full RGB endpoints.
*
* Quantization errors occur due to the limited precision we use for storage. These errors generally
* scale with quantization level, but are not actually independent of color encoding. In particular:
*
* - If we can use offset encoding then quantization error is halved.
* - If we can use blue-contraction then quantization error for RG is halved.
* - If we use HDR endpoints the quantization error is higher.
*
* Apart from these effects, we assume the error is proportional to the quantization step size.
*/
#include "astcenc_internal.h"
#include "astcenc_vecmathlib.h"
#include <assert.h>
/**
* @brief Compute the errors of the endpoint line options for one partition.
*
* Uncorrelated data assumes storing completely independent RGBA channels for each endpoint. Same
* chroma data assumes storing RGBA endpoints which pass though the origin (LDR only). RGBL data
* assumes storing RGB + lumashift (HDR only). Luminance error assumes storing RGB channels as a
* single value.
*
*
* @param pi The partition info data.
* @param partition_index The partition index to compule the error for.
* @param blk The image block.
* @param uncor_pline The endpoint line assuming uncorrelated endpoints.
* @param[out] uncor_err The computed error for the uncorrelated endpoint line.
* @param samec_pline The endpoint line assuming the same chroma for both endpoints.
* @param[out] samec_err The computed error for the uncorrelated endpoint line.
* @param rgbl_pline The endpoint line assuming RGB + lumashift data.
* @param[out] rgbl_err The computed error for the RGB + lumashift endpoint line.
* @param l_pline The endpoint line assuming luminance data.
* @param[out] l_err The computed error for the luminance endpoint line.
* @param[out] a_drop_err The computed error for dropping the alpha component.
*/
static void compute_error_squared_rgb_single_partition(
const partition_info& pi,
int partition_index,
const image_block& blk,
const processed_line3& uncor_pline,
float& uncor_err,
const processed_line3& samec_pline,
float& samec_err,
const processed_line3& rgbl_pline,
float& rgbl_err,
const processed_line3& l_pline,
float& l_err,
float& a_drop_err
) {
vfloat4 ews = blk.channel_weight;
unsigned int texel_count = pi.partition_texel_count[partition_index];
const uint8_t* texel_indexes = pi.texels_of_partition[partition_index];
promise(texel_count > 0);
vfloatacc a_drop_errv = vfloatacc::zero();
vfloat default_a(blk.get_default_alpha());
vfloatacc uncor_errv = vfloatacc::zero();
vfloat uncor_bs0(uncor_pline.bs.lane<0>());
vfloat uncor_bs1(uncor_pline.bs.lane<1>());
vfloat uncor_bs2(uncor_pline.bs.lane<2>());
vfloat uncor_amod0(uncor_pline.amod.lane<0>());
vfloat uncor_amod1(uncor_pline.amod.lane<1>());
vfloat uncor_amod2(uncor_pline.amod.lane<2>());
vfloatacc samec_errv = vfloatacc::zero();
vfloat samec_bs0(samec_pline.bs.lane<0>());
vfloat samec_bs1(samec_pline.bs.lane<1>());
vfloat samec_bs2(samec_pline.bs.lane<2>());
vfloatacc rgbl_errv = vfloatacc::zero();
vfloat rgbl_bs0(rgbl_pline.bs.lane<0>());
vfloat rgbl_bs1(rgbl_pline.bs.lane<1>());
vfloat rgbl_bs2(rgbl_pline.bs.lane<2>());
vfloat rgbl_amod0(rgbl_pline.amod.lane<0>());
vfloat rgbl_amod1(rgbl_pline.amod.lane<1>());
vfloat rgbl_amod2(rgbl_pline.amod.lane<2>());
vfloatacc l_errv = vfloatacc::zero();
vfloat l_bs0(l_pline.bs.lane<0>());
vfloat l_bs1(l_pline.bs.lane<1>());
vfloat l_bs2(l_pline.bs.lane<2>());
vint lane_ids = vint::lane_id();
for (unsigned int i = 0; i < texel_count; i += ASTCENC_SIMD_WIDTH)
{
const uint8_t* tix = texel_indexes + i;
vmask mask = lane_ids < vint(texel_count);
lane_ids += vint(ASTCENC_SIMD_WIDTH);
// Compute the error that arises from just ditching alpha
vfloat data_a = gatherf_byte_inds<vfloat>(blk.data_a, tix);
vfloat alpha_diff = data_a - default_a;
alpha_diff = alpha_diff * alpha_diff;
haccumulate(a_drop_errv, alpha_diff, mask);
vfloat data_r = gatherf_byte_inds<vfloat>(blk.data_r, tix);
vfloat data_g = gatherf_byte_inds<vfloat>(blk.data_g, tix);
vfloat data_b = gatherf_byte_inds<vfloat>(blk.data_b, tix);
// Compute uncorrelated error
vfloat param = data_r * uncor_bs0
+ data_g * uncor_bs1
+ data_b * uncor_bs2;
vfloat dist0 = (uncor_amod0 + param * uncor_bs0) - data_r;
vfloat dist1 = (uncor_amod1 + param * uncor_bs1) - data_g;
vfloat dist2 = (uncor_amod2 + param * uncor_bs2) - data_b;
vfloat error = dist0 * dist0 * ews.lane<0>()
+ dist1 * dist1 * ews.lane<1>()
+ dist2 * dist2 * ews.lane<2>();
haccumulate(uncor_errv, error, mask);
// Compute same chroma error - no "amod", its always zero
param = data_r * samec_bs0
+ data_g * samec_bs1
+ data_b * samec_bs2;
dist0 = (param * samec_bs0) - data_r;
dist1 = (param * samec_bs1) - data_g;
dist2 = (param * samec_bs2) - data_b;
error = dist0 * dist0 * ews.lane<0>()
+ dist1 * dist1 * ews.lane<1>()
+ dist2 * dist2 * ews.lane<2>();
haccumulate(samec_errv, error, mask);
// Compute rgbl error
param = data_r * rgbl_bs0
+ data_g * rgbl_bs1
+ data_b * rgbl_bs2;
dist0 = (rgbl_amod0 + param * rgbl_bs0) - data_r;
dist1 = (rgbl_amod1 + param * rgbl_bs1) - data_g;
dist2 = (rgbl_amod2 + param * rgbl_bs2) - data_b;
error = dist0 * dist0 * ews.lane<0>()
+ dist1 * dist1 * ews.lane<1>()
+ dist2 * dist2 * ews.lane<2>();
haccumulate(rgbl_errv, error, mask);
// Compute luma error - no "amod", its always zero
param = data_r * l_bs0
+ data_g * l_bs1
+ data_b * l_bs2;
dist0 = (param * l_bs0) - data_r;
dist1 = (param * l_bs1) - data_g;
dist2 = (param * l_bs2) - data_b;
error = dist0 * dist0 * ews.lane<0>()
+ dist1 * dist1 * ews.lane<1>()
+ dist2 * dist2 * ews.lane<2>();
haccumulate(l_errv, error, mask);
}
a_drop_err = hadd_s(a_drop_errv) * ews.lane<3>();
uncor_err = hadd_s(uncor_errv);
samec_err = hadd_s(samec_errv);
rgbl_err = hadd_s(rgbl_errv);
l_err = hadd_s(l_errv);
}
/**
* @brief For a given set of input colors and partitioning determine endpoint encode errors.
*
* This function determines the color error that results from RGB-scale encoding (LDR only),
* RGB-lumashift encoding (HDR only), luminance-encoding, and alpha drop. Also determines whether
* the endpoints are eligible for offset encoding or blue-contraction
*
* @param blk The image block.
* @param pi The partition info data.
* @param ep The idealized endpoints.
* @param[out] eci The resulting encoding choice error metrics.
*/
static void compute_encoding_choice_errors(
const image_block& blk,
const partition_info& pi,
const endpoints& ep,
encoding_choice_errors eci[BLOCK_MAX_PARTITIONS])
{
int partition_count = pi.partition_count;
promise(partition_count > 0);
partition_metrics pms[BLOCK_MAX_PARTITIONS];
compute_avgs_and_dirs_3_comp_rgb(pi, blk, pms);
for (int i = 0; i < partition_count; i++)
{
partition_metrics& pm = pms[i];
line3 uncor_rgb_lines;
line3 samec_rgb_lines; // for LDR-RGB-scale
line3 rgb_luma_lines; // for HDR-RGB-scale
processed_line3 uncor_rgb_plines;
processed_line3 samec_rgb_plines;
processed_line3 rgb_luma_plines;
processed_line3 luminance_plines;
float uncorr_rgb_error;
float samechroma_rgb_error;
float rgb_luma_error;
float luminance_rgb_error;
float alpha_drop_error;
uncor_rgb_lines.a = pm.avg;
uncor_rgb_lines.b = normalize_safe(pm.dir, unit3());
samec_rgb_lines.a = vfloat4::zero();
samec_rgb_lines.b = normalize_safe(pm.avg, unit3());
rgb_luma_lines.a = pm.avg;
rgb_luma_lines.b = unit3();
uncor_rgb_plines.amod = uncor_rgb_lines.a - uncor_rgb_lines.b * dot3(uncor_rgb_lines.a, uncor_rgb_lines.b);
uncor_rgb_plines.bs = uncor_rgb_lines.b;
// Same chroma always goes though zero, so this is simpler than the others
samec_rgb_plines.amod = vfloat4::zero();
samec_rgb_plines.bs = samec_rgb_lines.b;
rgb_luma_plines.amod = rgb_luma_lines.a - rgb_luma_lines.b * dot3(rgb_luma_lines.a, rgb_luma_lines.b);
rgb_luma_plines.bs = rgb_luma_lines.b;
// Luminance always goes though zero, so this is simpler than the others
luminance_plines.amod = vfloat4::zero();
luminance_plines.bs = unit3();
compute_error_squared_rgb_single_partition(
pi, i, blk,
uncor_rgb_plines, uncorr_rgb_error,
samec_rgb_plines, samechroma_rgb_error,
rgb_luma_plines, rgb_luma_error,
luminance_plines, luminance_rgb_error,
alpha_drop_error);
// Determine if we can offset encode RGB lanes
vfloat4 endpt0 = ep.endpt0[i];
vfloat4 endpt1 = ep.endpt1[i];
vfloat4 endpt_diff = abs(endpt1 - endpt0);
vmask4 endpt_can_offset = endpt_diff < vfloat4(0.12f * 65535.0f);
bool can_offset_encode = (mask(endpt_can_offset) & 0x7) == 0x7;
// Store out the settings
eci[i].rgb_scale_error = (samechroma_rgb_error - uncorr_rgb_error) * 0.7f; // empirical
eci[i].rgb_luma_error = (rgb_luma_error - uncorr_rgb_error) * 1.5f; // wild guess
eci[i].luminance_error = (luminance_rgb_error - uncorr_rgb_error) * 3.0f; // empirical
eci[i].alpha_drop_error = alpha_drop_error * 3.0f;
eci[i].can_offset_encode = can_offset_encode;
eci[i].can_blue_contract = !blk.is_luminance();
}
}
/**
* @brief For a given partition compute the error for every endpoint integer count and quant level.
*
* @param encode_hdr_rgb @c true if using HDR for RGB, @c false for LDR.
* @param encode_hdr_alpha @c true if using HDR for alpha, @c false for LDR.
* @param partition_index The partition index.
* @param pi The partition info.
* @param eci The encoding choice error metrics.
* @param ep The idealized endpoints.
* @param error_weight The resulting encoding choice error metrics.
* @param[out] best_error The best error for each integer count and quant level.
* @param[out] format_of_choice The preferred endpoint format for each integer count and quant level.
*/
static void compute_color_error_for_every_integer_count_and_quant_level(
bool encode_hdr_rgb,
bool encode_hdr_alpha,
int partition_index,
const partition_info& pi,
const encoding_choice_errors& eci,
const endpoints& ep,
vfloat4 error_weight,
float best_error[21][4],
uint8_t format_of_choice[21][4]
) {
int partition_size = pi.partition_texel_count[partition_index];
static const float baseline_quant_error[21 - QUANT_6] {
(65536.0f * 65536.0f / 18.0f) / (5 * 5),
(65536.0f * 65536.0f / 18.0f) / (7 * 7),
(65536.0f * 65536.0f / 18.0f) / (9 * 9),
(65536.0f * 65536.0f / 18.0f) / (11 * 11),
(65536.0f * 65536.0f / 18.0f) / (15 * 15),
(65536.0f * 65536.0f / 18.0f) / (19 * 19),
(65536.0f * 65536.0f / 18.0f) / (23 * 23),
(65536.0f * 65536.0f / 18.0f) / (31 * 31),
(65536.0f * 65536.0f / 18.0f) / (39 * 39),
(65536.0f * 65536.0f / 18.0f) / (47 * 47),
(65536.0f * 65536.0f / 18.0f) / (63 * 63),
(65536.0f * 65536.0f / 18.0f) / (79 * 79),
(65536.0f * 65536.0f / 18.0f) / (95 * 95),
(65536.0f * 65536.0f / 18.0f) / (127 * 127),
(65536.0f * 65536.0f / 18.0f) / (159 * 159),
(65536.0f * 65536.0f / 18.0f) / (191 * 191),
(65536.0f * 65536.0f / 18.0f) / (255 * 255)
};
vfloat4 ep0 = ep.endpt0[partition_index];
vfloat4 ep1 = ep.endpt1[partition_index];
float ep1_min = hmin_rgb_s(ep1);
ep1_min = astc::max(ep1_min, 0.0f);
float error_weight_rgbsum = hadd_rgb_s(error_weight);
float range_upper_limit_rgb = encode_hdr_rgb ? 61440.0f : 65535.0f;
float range_upper_limit_alpha = encode_hdr_alpha ? 61440.0f : 65535.0f;
// It is possible to get endpoint colors significantly outside [0,upper-limit] even if the
// input data are safely contained in [0,upper-limit]; we need to add an error term for this
vfloat4 offset(range_upper_limit_rgb, range_upper_limit_rgb, range_upper_limit_rgb, range_upper_limit_alpha);
vfloat4 ep0_range_error_high = max(ep0 - offset, 0.0f);
vfloat4 ep1_range_error_high = max(ep1 - offset, 0.0f);
vfloat4 ep0_range_error_low = min(ep0, 0.0f);
vfloat4 ep1_range_error_low = min(ep1, 0.0f);
vfloat4 sum_range_error =
(ep0_range_error_low * ep0_range_error_low) +
(ep1_range_error_low * ep1_range_error_low) +
(ep0_range_error_high * ep0_range_error_high) +
(ep1_range_error_high * ep1_range_error_high);
float rgb_range_error = dot3_s(sum_range_error, error_weight)
* 0.5f * static_cast<float>(partition_size);
float alpha_range_error = sum_range_error.lane<3>() * error_weight.lane<3>()
* 0.5f * static_cast<float>(partition_size);
if (encode_hdr_rgb)
{
// Collect some statistics
float af, cf;
if (ep1.lane<0>() > ep1.lane<1>() && ep1.lane<0>() > ep1.lane<2>())
{
af = ep1.lane<0>();
cf = ep1.lane<0>() - ep0.lane<0>();
}
else if (ep1.lane<1>() > ep1.lane<2>())
{
af = ep1.lane<1>();
cf = ep1.lane<1>() - ep0.lane<1>();
}
else
{
af = ep1.lane<2>();
cf = ep1.lane<2>() - ep0.lane<2>();
}
// Estimate of color-component spread in high endpoint color
float bf = af - ep1_min;
vfloat4 prd = (ep1 - vfloat4(cf)).swz<0, 1, 2>();
vfloat4 pdif = prd - ep0.swz<0, 1, 2>();
// Estimate of color-component spread in low endpoint color
float df = hmax_s(abs(pdif));
int b = static_cast<int>(bf);
int c = static_cast<int>(cf);
int d = static_cast<int>(df);
// Determine which one of the 6 submodes is likely to be used in case of an RGBO-mode
int rgbo_mode = 5; // 7 bits per component
// mode 4: 8 7 6
if (b < 32768 && c < 16384)
{
rgbo_mode = 4;
}
// mode 3: 9 6 7
if (b < 8192 && c < 16384)
{
rgbo_mode = 3;
}
// mode 2: 10 5 8
if (b < 2048 && c < 16384)
{
rgbo_mode = 2;
}
// mode 1: 11 6 5
if (b < 2048 && c < 1024)
{
rgbo_mode = 1;
}
// mode 0: 11 5 7
if (b < 1024 && c < 4096)
{
rgbo_mode = 0;
}
// Determine which one of the 9 submodes is likely to be used in case of an RGB-mode.
int rgb_mode = 8; // 8 bits per component, except 7 bits for blue
// mode 0: 9 7 6 7
if (b < 16384 && c < 8192 && d < 8192)
{
rgb_mode = 0;
}
// mode 1: 9 8 6 6
if (b < 32768 && c < 8192 && d < 4096)
{
rgb_mode = 1;
}
// mode 2: 10 6 7 7
if (b < 4096 && c < 8192 && d < 4096)
{
rgb_mode = 2;
}
// mode 3: 10 7 7 6
if (b < 8192 && c < 8192 && d < 2048)
{
rgb_mode = 3;
}
// mode 4: 11 8 6 5
if (b < 8192 && c < 2048 && d < 512)
{
rgb_mode = 4;
}
// mode 5: 11 6 8 6
if (b < 2048 && c < 8192 && d < 1024)
{
rgb_mode = 5;
}
// mode 6: 12 7 7 5
if (b < 2048 && c < 2048 && d < 256)
{
rgb_mode = 6;
}
// mode 7: 12 6 7 6
if (b < 1024 && c < 2048 && d < 512)
{
rgb_mode = 7;
}
static const float rgbo_error_scales[6] { 4.0f, 4.0f, 16.0f, 64.0f, 256.0f, 1024.0f };
static const float rgb_error_scales[9] { 64.0f, 64.0f, 16.0f, 16.0f, 4.0f, 4.0f, 1.0f, 1.0f, 384.0f };
float mode7mult = rgbo_error_scales[rgbo_mode] * 0.0015f; // Empirically determined ....
float mode11mult = rgb_error_scales[rgb_mode] * 0.010f; // Empirically determined ....
float lum_high = hadd_rgb_s(ep1) * (1.0f / 3.0f);
float lum_low = hadd_rgb_s(ep0) * (1.0f / 3.0f);
float lumdif = lum_high - lum_low;
float mode23mult = lumdif < 960 ? 4.0f : lumdif < 3968 ? 16.0f : 128.0f;
mode23mult *= 0.0005f; // Empirically determined ....
// Pick among the available HDR endpoint modes
for (int i = QUANT_2; i < QUANT_16; i++)
{
best_error[i][3] = ERROR_CALC_DEFAULT;
best_error[i][2] = ERROR_CALC_DEFAULT;
best_error[i][1] = ERROR_CALC_DEFAULT;
best_error[i][0] = ERROR_CALC_DEFAULT;
format_of_choice[i][3] = static_cast<uint8_t>(encode_hdr_alpha ? FMT_HDR_RGBA : FMT_HDR_RGB_LDR_ALPHA);
format_of_choice[i][2] = FMT_HDR_RGB;
format_of_choice[i][1] = FMT_HDR_RGB_SCALE;
format_of_choice[i][0] = FMT_HDR_LUMINANCE_LARGE_RANGE;
}
for (int i = QUANT_16; i <= QUANT_256; i++)
{
// The base_quant_error should depend on the scale-factor that would be used during
// actual encode of the color value
float base_quant_error = baseline_quant_error[i - QUANT_6] * static_cast<float>(partition_size);
float rgb_quantization_error = error_weight_rgbsum * base_quant_error * 2.0f;
float alpha_quantization_error = error_weight.lane<3>() * base_quant_error * 2.0f;
float rgba_quantization_error = rgb_quantization_error + alpha_quantization_error;
// For 8 integers, we have two encodings: one with HDR A and another one with LDR A
float full_hdr_rgba_error = rgba_quantization_error + rgb_range_error + alpha_range_error;
best_error[i][3] = full_hdr_rgba_error;
format_of_choice[i][3] = static_cast<uint8_t>(encode_hdr_alpha ? FMT_HDR_RGBA : FMT_HDR_RGB_LDR_ALPHA);
// For 6 integers, we have one HDR-RGB encoding
float full_hdr_rgb_error = (rgb_quantization_error * mode11mult) + rgb_range_error + eci.alpha_drop_error;
best_error[i][2] = full_hdr_rgb_error;
format_of_choice[i][2] = FMT_HDR_RGB;
// For 4 integers, we have one HDR-RGB-Scale encoding
float hdr_rgb_scale_error = (rgb_quantization_error * mode7mult) + rgb_range_error + eci.alpha_drop_error + eci.rgb_luma_error;
best_error[i][1] = hdr_rgb_scale_error;
format_of_choice[i][1] = FMT_HDR_RGB_SCALE;
// For 2 integers, we assume luminance-with-large-range
float hdr_luminance_error = (rgb_quantization_error * mode23mult) + rgb_range_error + eci.alpha_drop_error + eci.luminance_error;
best_error[i][0] = hdr_luminance_error;
format_of_choice[i][0] = FMT_HDR_LUMINANCE_LARGE_RANGE;
}
}
else
{
for (int i = QUANT_2; i < QUANT_6; i++)
{
best_error[i][3] = ERROR_CALC_DEFAULT;
best_error[i][2] = ERROR_CALC_DEFAULT;
best_error[i][1] = ERROR_CALC_DEFAULT;
best_error[i][0] = ERROR_CALC_DEFAULT;
format_of_choice[i][3] = FMT_RGBA;
format_of_choice[i][2] = FMT_RGB;
format_of_choice[i][1] = FMT_RGB_SCALE;
format_of_choice[i][0] = FMT_LUMINANCE;
}
float base_quant_error_rgb = error_weight_rgbsum * static_cast<float>(partition_size);
float base_quant_error_a = error_weight.lane<3>() * static_cast<float>(partition_size);
float base_quant_error_rgba = base_quant_error_rgb + base_quant_error_a;
float error_scale_bc_rgba = eci.can_blue_contract ? 0.625f : 1.0f;
float error_scale_oe_rgba = eci.can_offset_encode ? 0.5f : 1.0f;
float error_scale_bc_rgb = eci.can_blue_contract ? 0.5f : 1.0f;
float error_scale_oe_rgb = eci.can_offset_encode ? 0.25f : 1.0f;
// Pick among the available LDR endpoint modes
for (int i = QUANT_6; i <= QUANT_256; i++)
{
// Offset encoding not possible at higher quant levels
if (i >= QUANT_192)
{
error_scale_oe_rgba = 1.0f;
error_scale_oe_rgb = 1.0f;
}
float base_quant_error = baseline_quant_error[i - QUANT_6];
float quant_error_rgb = base_quant_error_rgb * base_quant_error;
float quant_error_rgba = base_quant_error_rgba * base_quant_error;
// 8 integers can encode as RGBA+RGBA
float full_ldr_rgba_error = quant_error_rgba
* error_scale_bc_rgba
* error_scale_oe_rgba
+ rgb_range_error
+ alpha_range_error;
best_error[i][3] = full_ldr_rgba_error;
format_of_choice[i][3] = FMT_RGBA;
// 6 integers can encode as RGB+RGB or RGBS+AA
float full_ldr_rgb_error = quant_error_rgb
* error_scale_bc_rgb
* error_scale_oe_rgb
+ rgb_range_error
+ eci.alpha_drop_error;
float rgbs_alpha_error = quant_error_rgba
+ eci.rgb_scale_error
+ rgb_range_error
+ alpha_range_error;
if (rgbs_alpha_error < full_ldr_rgb_error)
{
best_error[i][2] = rgbs_alpha_error;
format_of_choice[i][2] = FMT_RGB_SCALE_ALPHA;
}
else
{
best_error[i][2] = full_ldr_rgb_error;
format_of_choice[i][2] = FMT_RGB;
}
// 4 integers can encode as RGBS or LA+LA
float ldr_rgbs_error = quant_error_rgb
+ rgb_range_error
+ eci.alpha_drop_error
+ eci.rgb_scale_error;
float lum_alpha_error = quant_error_rgba
+ rgb_range_error
+ alpha_range_error
+ eci.luminance_error;
if (ldr_rgbs_error < lum_alpha_error)
{
best_error[i][1] = ldr_rgbs_error;
format_of_choice[i][1] = FMT_RGB_SCALE;
}
else
{
best_error[i][1] = lum_alpha_error;
format_of_choice[i][1] = FMT_LUMINANCE_ALPHA;
}
// 2 integers can encode as L+L
float luminance_error = quant_error_rgb
+ rgb_range_error
+ eci.alpha_drop_error
+ eci.luminance_error;
best_error[i][0] = luminance_error;
format_of_choice[i][0] = FMT_LUMINANCE;
}
}
}
/**
* @brief For one partition compute the best format and quantization for a given bit count.
*
* @param best_combined_error The best error for each quant level and integer count.
* @param best_combined_format The best format for each quant level and integer count.
* @param bits_available The number of bits available for encoding.
* @param[out] best_quant_level The output best color quant level.
* @param[out] best_format The output best color format.
*
* @return The output error for the best pairing.
*/
static float one_partition_find_best_combination_for_bitcount(
const float best_combined_error[21][4],
const uint8_t best_combined_format[21][4],
int bits_available,
uint8_t& best_quant_level,
uint8_t& best_format
) {
int best_integer_count = 0;
float best_integer_count_error = ERROR_CALC_DEFAULT;
for (int integer_count = 1; integer_count <= 4; integer_count++)
{
// Compute the quantization level for a given number of integers and a given number of bits
int quant_level = quant_mode_table[integer_count][bits_available];
// Don't have enough bits to represent a given endpoint format at all!
if (quant_level < QUANT_6)
{
continue;
}
float integer_count_error = best_combined_error[quant_level][integer_count - 1];
if (integer_count_error < best_integer_count_error)
{
best_integer_count_error = integer_count_error;
best_integer_count = integer_count - 1;
}
}
int ql = quant_mode_table[best_integer_count + 1][bits_available];
best_quant_level = static_cast<uint8_t>(ql);
best_format = FMT_LUMINANCE;
if (ql >= QUANT_6)
{
best_format = best_combined_format[ql][best_integer_count];
}
return best_integer_count_error;
}
/**
* @brief For 2 partitions compute the best format combinations for every pair of quant mode and integer count.
*
* @param best_error The best error for a single endpoint quant level and integer count.
* @param best_format The best format for a single endpoint quant level and integer count.
* @param[out] best_combined_error The best combined error pairings for the 2 partitions.
* @param[out] best_combined_format The best combined format pairings for the 2 partitions.
*/
static void two_partitions_find_best_combination_for_every_quantization_and_integer_count(
const float best_error[2][21][4], // indexed by (partition, quant-level, integer-pair-count-minus-1)
const uint8_t best_format[2][21][4],
float best_combined_error[21][7], // indexed by (quant-level, integer-pair-count-minus-2)
uint8_t best_combined_format[21][7][2]
) {
for (int i = QUANT_2; i <= QUANT_256; i++)
{
for (int j = 0; j < 7; j++)
{
best_combined_error[i][j] = ERROR_CALC_DEFAULT;
}
}
for (int quant = QUANT_6; quant <= QUANT_256; quant++)
{
for (int i = 0; i < 4; i++) // integer-count for first endpoint-pair
{
for (int j = 0; j < 4; j++) // integer-count for second endpoint-pair
{
int low2 = astc::min(i, j);
int high2 = astc::max(i, j);
if ((high2 - low2) > 1)
{
continue;
}
int intcnt = i + j;
float errorterm = astc::min(best_error[0][quant][i] + best_error[1][quant][j], 1e10f);
if (errorterm <= best_combined_error[quant][intcnt])
{
best_combined_error[quant][intcnt] = errorterm;
best_combined_format[quant][intcnt][0] = best_format[0][quant][i];
best_combined_format[quant][intcnt][1] = best_format[1][quant][j];
}
}
}
}
}
/**
* @brief For 2 partitions compute the best format and quantization for a given bit count.
*
* @param best_combined_error The best error for each quant level and integer count.
* @param best_combined_format The best format for each quant level and integer count.
* @param bits_available The number of bits available for encoding.
* @param[out] best_quant_level The output best color quant level.
* @param[out] best_quant_level_mod The output best color quant level assuming two more bits are available.
* @param[out] best_formats The output best color formats.
*
* @return The output error for the best pairing.
*/
static float two_partitions_find_best_combination_for_bitcount(
float best_combined_error[21][7],
uint8_t best_combined_format[21][7][2],
int bits_available,
uint8_t& best_quant_level,
uint8_t& best_quant_level_mod,
uint8_t* best_formats
) {
int best_integer_count = 0;
float best_integer_count_error = ERROR_CALC_DEFAULT;
for (int integer_count = 2; integer_count <= 8; integer_count++)
{
// Compute the quantization level for a given number of integers and a given number of bits
int quant_level = quant_mode_table[integer_count][bits_available];
// Don't have enough bits to represent a given endpoint format at all!
if (quant_level < QUANT_6)
{
break;
}
float integer_count_error = best_combined_error[quant_level][integer_count - 2];
if (integer_count_error < best_integer_count_error)
{
best_integer_count_error = integer_count_error;
best_integer_count = integer_count;
}
}
int ql = quant_mode_table[best_integer_count][bits_available];
int ql_mod = quant_mode_table[best_integer_count][bits_available + 2];
best_quant_level = static_cast<uint8_t>(ql);
best_quant_level_mod = static_cast<uint8_t>(ql_mod);
if (ql >= QUANT_6)
{
for (int i = 0; i < 2; i++)
{
best_formats[i] = best_combined_format[ql][best_integer_count - 2][i];
}
}
else
{
for (int i = 0; i < 2; i++)
{
best_formats[i] = FMT_LUMINANCE;
}
}
return best_integer_count_error;
}
/**
* @brief For 3 partitions compute the best format combinations for every pair of quant mode and integer count.
*
* @param best_error The best error for a single endpoint quant level and integer count.
* @param best_format The best format for a single endpoint quant level and integer count.
* @param[out] best_combined_error The best combined error pairings for the 3 partitions.
* @param[out] best_combined_format The best combined format pairings for the 3 partitions.
*/
static void three_partitions_find_best_combination_for_every_quantization_and_integer_count(
const float best_error[3][21][4], // indexed by (partition, quant-level, integer-count)
const uint8_t best_format[3][21][4],
float best_combined_error[21][10],
uint8_t best_combined_format[21][10][3]
) {
for (int i = QUANT_2; i <= QUANT_256; i++)
{
for (int j = 0; j < 10; j++)
{
best_combined_error[i][j] = ERROR_CALC_DEFAULT;
}
}
for (int quant = QUANT_6; quant <= QUANT_256; quant++)
{
for (int i = 0; i < 4; i++) // integer-count for first endpoint-pair
{
for (int j = 0; j < 4; j++) // integer-count for second endpoint-pair
{
int low2 = astc::min(i, j);
int high2 = astc::max(i, j);
if ((high2 - low2) > 1)
{
continue;
}
for (int k = 0; k < 4; k++) // integer-count for third endpoint-pair
{
int low3 = astc::min(k, low2);
int high3 = astc::max(k, high2);
if ((high3 - low3) > 1)
{
continue;
}
int intcnt = i + j + k;
float errorterm = astc::min(best_error[0][quant][i] + best_error[1][quant][j] + best_error[2][quant][k], 1e10f);
if (errorterm <= best_combined_error[quant][intcnt])
{
best_combined_error[quant][intcnt] = errorterm;
best_combined_format[quant][intcnt][0] = best_format[0][quant][i];
best_combined_format[quant][intcnt][1] = best_format[1][quant][j];
best_combined_format[quant][intcnt][2] = best_format[2][quant][k];
}
}
}
}
}
}
/**
* @brief For 3 partitions compute the best format and quantization for a given bit count.
*
* @param best_combined_error The best error for each quant level and integer count.
* @param best_combined_format The best format for each quant level and integer count.
* @param bits_available The number of bits available for encoding.
* @param[out] best_quant_level The output best color quant level.
* @param[out] best_quant_level_mod The output best color quant level assuming two more bits are available.
* @param[out] best_formats The output best color formats.
*
* @return The output error for the best pairing.
*/
static float three_partitions_find_best_combination_for_bitcount(
const float best_combined_error[21][10],
const uint8_t best_combined_format[21][10][3],
int bits_available,
uint8_t& best_quant_level,
uint8_t& best_quant_level_mod,
uint8_t* best_formats
) {
int best_integer_count = 0;
float best_integer_count_error = ERROR_CALC_DEFAULT;
for (int integer_count = 3; integer_count <= 9; integer_count++)
{
// Compute the quantization level for a given number of integers and a given number of bits
int quant_level = quant_mode_table[integer_count][bits_available];
// Don't have enough bits to represent a given endpoint format at all!
if (quant_level < QUANT_6)
{
break;
}
float integer_count_error = best_combined_error[quant_level][integer_count - 3];
if (integer_count_error < best_integer_count_error)
{
best_integer_count_error = integer_count_error;
best_integer_count = integer_count;
}
}
int ql = quant_mode_table[best_integer_count][bits_available];
int ql_mod = quant_mode_table[best_integer_count][bits_available + 5];
best_quant_level = static_cast<uint8_t>(ql);
best_quant_level_mod = static_cast<uint8_t>(ql_mod);
if (ql >= QUANT_6)
{
for (int i = 0; i < 3; i++)
{
best_formats[i] = best_combined_format[ql][best_integer_count - 3][i];
}
}
else
{
for (int i = 0; i < 3; i++)
{
best_formats[i] = FMT_LUMINANCE;
}
}
return best_integer_count_error;
}
/**
* @brief For 4 partitions compute the best format combinations for every pair of quant mode and integer count.
*
* @param best_error The best error for a single endpoint quant level and integer count.
* @param best_format The best format for a single endpoint quant level and integer count.
* @param[out] best_combined_error The best combined error pairings for the 4 partitions.
* @param[out] best_combined_format The best combined format pairings for the 4 partitions.
*/
static void four_partitions_find_best_combination_for_every_quantization_and_integer_count(
const float best_error[4][21][4], // indexed by (partition, quant-level, integer-count)
const uint8_t best_format[4][21][4],
float best_combined_error[21][13],
uint8_t best_combined_format[21][13][4]
) {
for (int i = QUANT_2; i <= QUANT_256; i++)
{
for (int j = 0; j < 13; j++)
{
best_combined_error[i][j] = ERROR_CALC_DEFAULT;
}
}
for (int quant = QUANT_6; quant <= QUANT_256; quant++)
{
for (int i = 0; i < 4; i++) // integer-count for first endpoint-pair
{
for (int j = 0; j < 4; j++) // integer-count for second endpoint-pair
{
int low2 = astc::min(i, j);
int high2 = astc::max(i, j);
if ((high2 - low2) > 1)
{
continue;
}
for (int k = 0; k < 4; k++) // integer-count for third endpoint-pair
{
int low3 = astc::min(k, low2);
int high3 = astc::max(k, high2);
if ((high3 - low3) > 1)
{
continue;
}
for (int l = 0; l < 4; l++) // integer-count for fourth endpoint-pair
{
int low4 = astc::min(l, low3);
int high4 = astc::max(l, high3);
if ((high4 - low4) > 1)
{
continue;
}
int intcnt = i + j + k + l;
float errorterm = astc::min(best_error[0][quant][i] + best_error[1][quant][j] + best_error[2][quant][k] + best_error[3][quant][l], 1e10f);
if (errorterm <= best_combined_error[quant][intcnt])
{
best_combined_error[quant][intcnt] = errorterm;
best_combined_format[quant][intcnt][0] = best_format[0][quant][i];
best_combined_format[quant][intcnt][1] = best_format[1][quant][j];
best_combined_format[quant][intcnt][2] = best_format[2][quant][k];
best_combined_format[quant][intcnt][3] = best_format[3][quant][l];
}
}
}
}
}
}
}
/**
* @brief For 4 partitions compute the best format and quantization for a given bit count.
*
* @param best_combined_error The best error for each quant level and integer count.
* @param best_combined_format The best format for each quant level and integer count.
* @param bits_available The number of bits available for encoding.
* @param[out] best_quant_level The output best color quant level.
* @param[out] best_quant_level_mod The output best color quant level assuming two more bits are available.
* @param[out] best_formats The output best color formats.
*
* @return best_error The output error for the best pairing.
*/
static float four_partitions_find_best_combination_for_bitcount(
const float best_combined_error[21][13],
const uint8_t best_combined_format[21][13][4],
int bits_available,
uint8_t& best_quant_level,
uint8_t& best_quant_level_mod,
uint8_t* best_formats
) {
int best_integer_count = 0;
float best_integer_count_error = ERROR_CALC_DEFAULT;
for (int integer_count = 4; integer_count <= 9; integer_count++)
{
// Compute the quantization level for a given number of integers and a given number of bits
int quant_level = quant_mode_table[integer_count][bits_available];
// Don't have enough bits to represent a given endpoint format at all!
if (quant_level < QUANT_6)
{
break;
}
float integer_count_error = best_combined_error[quant_level][integer_count - 4];
if (integer_count_error < best_integer_count_error)
{
best_integer_count_error = integer_count_error;
best_integer_count = integer_count;
}
}
int ql = quant_mode_table[best_integer_count][bits_available];
int ql_mod = quant_mode_table[best_integer_count][bits_available + 8];
best_quant_level = static_cast<uint8_t>(ql);
best_quant_level_mod = static_cast<uint8_t>(ql_mod);
if (ql >= QUANT_6)
{
for (int i = 0; i < 4; i++)
{
best_formats[i] = best_combined_format[ql][best_integer_count - 4][i];
}
}
else
{
for (int i = 0; i < 4; i++)
{
best_formats[i] = FMT_LUMINANCE;
}
}
return best_integer_count_error;
}
/* See header for documentation. */
unsigned int compute_ideal_endpoint_formats(
const partition_info& pi,
const image_block& blk,
const endpoints& ep,
// bitcounts and errors computed for the various quantization methods
const int8_t* qwt_bitcounts,
const float* qwt_errors,
unsigned int tune_candidate_limit,
unsigned int start_block_mode,
unsigned int end_block_mode,
// output data
uint8_t partition_format_specifiers[TUNE_MAX_TRIAL_CANDIDATES][BLOCK_MAX_PARTITIONS],
int block_mode[TUNE_MAX_TRIAL_CANDIDATES],
quant_method quant_level[TUNE_MAX_TRIAL_CANDIDATES],
quant_method quant_level_mod[TUNE_MAX_TRIAL_CANDIDATES],
compression_working_buffers& tmpbuf
) {
int partition_count = pi.partition_count;
promise(partition_count > 0);
bool encode_hdr_rgb = static_cast<bool>(blk.rgb_lns[0]);
bool encode_hdr_alpha = static_cast<bool>(blk.alpha_lns[0]);
// Compute the errors that result from various encoding choices (such as using luminance instead
// of RGB, discarding Alpha, using RGB-scale in place of two separate RGB endpoints and so on)
encoding_choice_errors eci[BLOCK_MAX_PARTITIONS];
compute_encoding_choice_errors(blk, pi, ep, eci);
float best_error[BLOCK_MAX_PARTITIONS][21][4];
uint8_t format_of_choice[BLOCK_MAX_PARTITIONS][21][4];
for (int i = 0; i < partition_count; i++)
{
compute_color_error_for_every_integer_count_and_quant_level(
encode_hdr_rgb, encode_hdr_alpha, i,
pi, eci[i], ep, blk.channel_weight, best_error[i],
format_of_choice[i]);
}
float* errors_of_best_combination = tmpbuf.errors_of_best_combination;
uint8_t* best_quant_levels = tmpbuf.best_quant_levels;
uint8_t* best_quant_levels_mod = tmpbuf.best_quant_levels_mod;
uint8_t (&best_ep_formats)[WEIGHTS_MAX_BLOCK_MODES][BLOCK_MAX_PARTITIONS] = tmpbuf.best_ep_formats;
// Ensure that the first iteration understep contains data that will never be picked
vfloat clear_error(ERROR_CALC_DEFAULT);
vint clear_quant(0);
size_t packed_start_block_mode = round_down_to_simd_multiple_vla(start_block_mode);
storea(clear_error, errors_of_best_combination + packed_start_block_mode);
store_nbytes(clear_quant, best_quant_levels + packed_start_block_mode);
store_nbytes(clear_quant, best_quant_levels_mod + packed_start_block_mode);
// Ensure that last iteration overstep contains data that will never be picked
size_t packed_end_block_mode = round_down_to_simd_multiple_vla(end_block_mode - 1);
storea(clear_error, errors_of_best_combination + packed_end_block_mode);
store_nbytes(clear_quant, best_quant_levels + packed_end_block_mode);
store_nbytes(clear_quant, best_quant_levels_mod + packed_end_block_mode);
// Track a scalar best to avoid expensive search at least once ...
float error_of_best_combination = ERROR_CALC_DEFAULT;
int index_of_best_combination = -1;
// The block contains 1 partition
if (partition_count == 1)
{
for (unsigned int i = start_block_mode; i < end_block_mode; i++)
{
if (qwt_errors[i] >= ERROR_CALC_DEFAULT)
{
errors_of_best_combination[i] = ERROR_CALC_DEFAULT;
continue;
}
float error_of_best = one_partition_find_best_combination_for_bitcount(
best_error[0], format_of_choice[0], qwt_bitcounts[i],
best_quant_levels[i], best_ep_formats[i][0]);
float total_error = error_of_best + qwt_errors[i];
errors_of_best_combination[i] = total_error;
best_quant_levels_mod[i] = best_quant_levels[i];
if (total_error < error_of_best_combination)
{
error_of_best_combination = total_error;
index_of_best_combination = i;
}
}
}
// The block contains 2 partitions
else if (partition_count == 2)
{
float combined_best_error[21][7];
uint8_t formats_of_choice[21][7][2];
two_partitions_find_best_combination_for_every_quantization_and_integer_count(
best_error, format_of_choice, combined_best_error, formats_of_choice);
assert(start_block_mode == 0);
for (unsigned int i = 0; i < end_block_mode; i++)
{
if (qwt_errors[i] >= ERROR_CALC_DEFAULT)
{
errors_of_best_combination[i] = ERROR_CALC_DEFAULT;
continue;
}
float error_of_best = two_partitions_find_best_combination_for_bitcount(
combined_best_error, formats_of_choice, qwt_bitcounts[i],
best_quant_levels[i], best_quant_levels_mod[i],
best_ep_formats[i]);
float total_error = error_of_best + qwt_errors[i];
errors_of_best_combination[i] = total_error;
if (total_error < error_of_best_combination)
{
error_of_best_combination = total_error;
index_of_best_combination = i;
}
}
}
// The block contains 3 partitions
else if (partition_count == 3)
{
float combined_best_error[21][10];
uint8_t formats_of_choice[21][10][3];
three_partitions_find_best_combination_for_every_quantization_and_integer_count(
best_error, format_of_choice, combined_best_error, formats_of_choice);
assert(start_block_mode == 0);
for (unsigned int i = 0; i < end_block_mode; i++)
{
if (qwt_errors[i] >= ERROR_CALC_DEFAULT)
{
errors_of_best_combination[i] = ERROR_CALC_DEFAULT;
continue;
}
float error_of_best = three_partitions_find_best_combination_for_bitcount(
combined_best_error, formats_of_choice, qwt_bitcounts[i],
best_quant_levels[i], best_quant_levels_mod[i],
best_ep_formats[i]);
float total_error = error_of_best + qwt_errors[i];
errors_of_best_combination[i] = total_error;
if (total_error < error_of_best_combination)
{
error_of_best_combination = total_error;
index_of_best_combination = i;
}
}
}
// The block contains 4 partitions
else // if (partition_count == 4)
{
assert(partition_count == 4);
float combined_best_error[21][13];
uint8_t formats_of_choice[21][13][4];
four_partitions_find_best_combination_for_every_quantization_and_integer_count(
best_error, format_of_choice, combined_best_error, formats_of_choice);
assert(start_block_mode == 0);
for (unsigned int i = 0; i < end_block_mode; i++)
{
if (qwt_errors[i] >= ERROR_CALC_DEFAULT)
{
errors_of_best_combination[i] = ERROR_CALC_DEFAULT;
continue;
}
float error_of_best = four_partitions_find_best_combination_for_bitcount(
combined_best_error, formats_of_choice, qwt_bitcounts[i],
best_quant_levels[i], best_quant_levels_mod[i],
best_ep_formats[i]);
float total_error = error_of_best + qwt_errors[i];
errors_of_best_combination[i] = total_error;
if (total_error < error_of_best_combination)
{
error_of_best_combination = total_error;
index_of_best_combination = i;
}
}
}
int best_error_weights[TUNE_MAX_TRIAL_CANDIDATES];
// Fast path the first result and avoid the list search for trial 0
best_error_weights[0] = index_of_best_combination;
if (index_of_best_combination >= 0)
{
errors_of_best_combination[index_of_best_combination] = ERROR_CALC_DEFAULT;
}
// Search the remaining results and pick the best candidate modes for trial 1+
for (unsigned int i = 1; i < tune_candidate_limit; i++)
{
vint vbest_error_index(-1);
vfloat vbest_ep_error(ERROR_CALC_DEFAULT);
// TODO: This should use size_t for the inputs of start/end_block_mode
// to avoid some of this type conversion, but that propagates and will
// need a bigger PR to fix
size_t start_mode = round_down_to_simd_multiple_vla(start_block_mode);
vint lane_ids = vint::lane_id() + vint_from_size(start_mode);
for (size_t j = start_mode; j < end_block_mode; j += ASTCENC_SIMD_WIDTH)
{
vfloat err = vfloat(errors_of_best_combination + j);
vmask mask = err < vbest_ep_error;
vbest_ep_error = select(vbest_ep_error, err, mask);
vbest_error_index = select(vbest_error_index, lane_ids, mask);
lane_ids += vint(ASTCENC_SIMD_WIDTH);
}
// Pick best mode from the SIMD result, using lowest matching index to ensure invariance
vmask lanes_min_error = vbest_ep_error == hmin(vbest_ep_error);
vbest_error_index = select(vint(0x7FFFFFFF), vbest_error_index, lanes_min_error);
int best_error_index = hmin_s(vbest_error_index);
best_error_weights[i] = best_error_index;
// Max the error for this candidate so we don't pick it again
if (best_error_index >= 0)
{
errors_of_best_combination[best_error_index] = ERROR_CALC_DEFAULT;
}
// Early-out if no more candidates are valid
else
{
break;
}
}
for (unsigned int i = 0; i < tune_candidate_limit; i++)
{
if (best_error_weights[i] < 0)
{
return i;
}
block_mode[i] = best_error_weights[i];
quant_level[i] = static_cast<quant_method>(best_quant_levels[best_error_weights[i]]);
quant_level_mod[i] = static_cast<quant_method>(best_quant_levels_mod[best_error_weights[i]]);
assert(quant_level[i] >= QUANT_6 && quant_level[i] <= QUANT_256);
assert(quant_level_mod[i] >= QUANT_6 && quant_level_mod[i] <= QUANT_256);
for (int j = 0; j < partition_count; j++)
{
partition_format_specifiers[i][j] = best_ep_formats[best_error_weights[i]][j];
}
}
return tune_candidate_limit;
}
#endif
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