// SPDX-License-Identifier: Apache-2.0 // ---------------------------------------------------------------------------- // Copyright 2011-2022 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 /** * @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) { vint 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(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(blk.data_r, tix); vfloat data_g = gatherf(blk.data_g, tix); vfloat data_b = gatherf(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(partition_size); float alpha_range_error = sum_range_error.lane<3>() * error_weight.lane<3>() * 0.5f * static_cast(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(bf); int c = static_cast(cf); int d = static_cast(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(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(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(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(partition_size); float base_quant_error_a = error_weight.lane<3>() * static_cast(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(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(ql); best_quant_level_mod = static_cast(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(ql); best_quant_level_mod = static_cast(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(ql); best_quant_level_mod = static_cast(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(blk.rgb_lns[0]); bool encode_hdr_alpha = static_cast(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); unsigned int 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 unsigned int 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); start_block_mode = round_down_to_simd_multiple_vla(start_block_mode); vint lane_ids = vint::lane_id() + vint(start_block_mode); for (unsigned int j = start_block_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); vbest_error_index = hmin(vbest_error_index); int best_error_index = vbest_error_index.lane<0>(); 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(best_quant_levels[best_error_weights[i]]); quant_level_mod[i] = static_cast(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