X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=resample_effect.cpp;h=9c8caf3bb77ed58bf2d143dcc2b3b837b81a001c;hp=f4808c4560437288a327156f10a2f0e794e1f991;hb=34776d3ed2565ee834405e575bf3bfc7f7933e36;hpb=c62391987241f1482a99b6f6417fbec1d0ef2344 diff --git a/resample_effect.cpp b/resample_effect.cpp index f4808c4..9c8caf3 100644 --- a/resample_effect.cpp +++ b/resample_effect.cpp @@ -1,4 +1,6 @@ // Three-lobed Lanczos, the most common choice. +// Note that if you change this, the accuracy for LANCZOS_TABLE_SIZE +// needs to be recomputed. #define LANCZOS_RADIUS 3.0 #include @@ -7,6 +9,9 @@ #include #include #include +#include +#include +#include #include "effect_chain.h" #include "effect_util.h" @@ -15,6 +20,7 @@ #include "resample_effect.h" #include "util.h" +using namespace Eigen; using namespace std; namespace movit { @@ -36,15 +42,67 @@ float sinc(float x) } } -float lanczos_weight(float x, float a) +float lanczos_weight(float x) { - if (fabs(x) > a) { + if (fabs(x) > LANCZOS_RADIUS) { return 0.0f; } else { - return sinc(M_PI * x) * sinc(M_PI * x / a); + return sinc(M_PI * x) * sinc((M_PI / LANCZOS_RADIUS) * x); } } +// The weight function can be expensive to compute over and over again +// (which will happen during e.g. a zoom), but it is also easy to interpolate +// linearly. We compute the right half of the function (in the range of +// 0..LANCZOS_RADIUS), with two guard elements for easier interpolation, and +// linearly interpolate to get our function. +// +// We want to scale the table so that the maximum error is always smaller +// than 1e-6. As per http://www-solar.mcs.st-andrews.ac.uk/~clare/Lectures/num-analysis/Numan_chap3.pdf, +// the error for interpolating a function linearly between points [a,b] is +// +// e = 1/2 (x-a)(x-b) f''(u_x) +// +// for some point u_x in [a,b] (where f(x) is our Lanczos function; we're +// assuming LANCZOS_RADIUS=3 from here on). Obviously this is bounded by +// f''(x) over the entire range. Numeric optimization shows the maximum of +// |f''(x)| to be in x=1.09369819474562880, with the value 2.40067758733152381. +// So if the steps between consecutive values are called d, we get +// +// |e| <= 1/2 (d/2)^2 2.4007 +// |e| <= 0.1367 d^2 +// +// Solve for e = 1e-6 yields a step size of 0.0027, which to cover the range +// 0..3 needs 1109 steps. We round up to the next power of two, just to be sure. +// +// You need to call lanczos_table_init_done before the first call to +// lanczos_weight_cached. +#define LANCZOS_TABLE_SIZE 2048 +bool lanczos_table_init_done = false; +float lanczos_table[LANCZOS_TABLE_SIZE + 2]; + +void init_lanczos_table() +{ + for (unsigned i = 0; i < LANCZOS_TABLE_SIZE + 2; ++i) { + lanczos_table[i] = lanczos_weight(float(i) * (LANCZOS_RADIUS / LANCZOS_TABLE_SIZE)); + } + lanczos_table_init_done = true; +} + +float lanczos_weight_cached(float x) +{ + x = fabs(x); + if (x > LANCZOS_RADIUS) { + return 0.0f; + } + float table_pos = x * (LANCZOS_TABLE_SIZE / LANCZOS_RADIUS); + int table_pos_int = int(table_pos); // Truncate towards zero. + float table_pos_frac = table_pos - table_pos_int; + assert(table_pos < LANCZOS_TABLE_SIZE + 2); + return lanczos_table[table_pos_int] + + table_pos_frac * (lanczos_table[table_pos_int + 1] - lanczos_table[table_pos_int]); +} + // Euclid's algorithm, from Wikipedia. unsigned gcd(unsigned a, unsigned b) { @@ -57,9 +115,24 @@ unsigned gcd(unsigned a, unsigned b) } template -unsigned combine_samples(const Tap *src, Tap *dst, unsigned src_size, unsigned num_src_samples, unsigned max_samples_saved) +unsigned combine_samples(const Tap *src, Tap *dst, float num_subtexels, float inv_num_subtexels, unsigned num_src_samples, unsigned max_samples_saved) { + // Cut off near-zero values at both sides. unsigned num_samples_saved = 0; + while (num_samples_saved < max_samples_saved && + num_src_samples > 0 && + fabs(src[0].weight) < 1e-6) { + ++src; + --num_src_samples; + ++num_samples_saved; + } + while (num_samples_saved < max_samples_saved && + num_src_samples > 0 && + fabs(src[num_src_samples - 1].weight) < 1e-6) { + --num_src_samples; + ++num_samples_saved; + } + for (unsigned i = 0, j = 0; i < num_src_samples; ++i, ++j) { // Copy the sample directly; it will be overwritten later if we can combine. if (dst != NULL) { @@ -88,9 +161,9 @@ unsigned combine_samples(const Tap *src, Tap *dst, unsigned sr float pos2 = src[i + 1].pos; assert(pos2 > pos1); - fp16_int_t pos, total_weight; + DestFloat pos, total_weight; float sum_sq_error; - combine_two_samples(w1, w2, pos1, pos2, src_size, &pos, &total_weight, &sum_sq_error); + combine_two_samples(w1, w2, pos1, pos2, num_subtexels, inv_num_subtexels, &pos, &total_weight, &sum_sq_error); // If the interpolation error is larger than that of about sqrt(2) of // a level at 8-bit precision, don't combine. (You'd think 1.0 was enough, @@ -113,6 +186,23 @@ unsigned combine_samples(const Tap *src, Tap *dst, unsigned sr return num_samples_saved; } +// Normalize so that the sum becomes one. Note that we do it twice; +// this sometimes helps a tiny little bit when we have many samples. +template +void normalize_sum(Tap* vals, unsigned num) +{ + for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) { + float sum = 0.0; + for (unsigned i = 0; i < num; ++i) { + sum += to_fp32(vals[i].weight); + } + float inv_sum = 1.0 / sum; + for (unsigned i = 0; i < num; ++i) { + vals[i].weight = from_fp32(to_fp32(vals[i].weight) * inv_sum); + } + } +} + // Make use of the bilinear filtering in the GPU to reduce the number of samples // we need to make. This is a bit more complex than BlurEffect since we cannot combine // two neighboring samples if their weights have differing signs, so we first need to @@ -124,36 +214,29 @@ unsigned combine_samples(const Tap *src, Tap *dst, unsigned sr template unsigned combine_many_samples(const Tap *weights, unsigned src_size, unsigned src_samples, unsigned dst_samples, Tap **bilinear_weights) { - int src_bilinear_samples = 0; - for (unsigned y = 0; y < dst_samples; ++y) { - unsigned num_samples_saved = combine_samples(weights + y * src_samples, NULL, src_size, src_samples, UINT_MAX); - src_bilinear_samples = max(src_bilinear_samples, src_samples - num_samples_saved); + float num_subtexels = src_size / movit_texel_subpixel_precision; + float inv_num_subtexels = movit_texel_subpixel_precision / src_size; + + unsigned max_samples_saved = UINT_MAX; + for (unsigned y = 0; y < dst_samples && max_samples_saved > 0; ++y) { + unsigned num_samples_saved = combine_samples(weights + y * src_samples, NULL, num_subtexels, inv_num_subtexels, src_samples, max_samples_saved); + max_samples_saved = min(max_samples_saved, num_samples_saved); } // Now that we know the right width, actually combine the samples. + unsigned src_bilinear_samples = src_samples - max_samples_saved; *bilinear_weights = new Tap[dst_samples * src_bilinear_samples]; for (unsigned y = 0; y < dst_samples; ++y) { Tap *bilinear_weights_ptr = *bilinear_weights + y * src_bilinear_samples; unsigned num_samples_saved = combine_samples( weights + y * src_samples, bilinear_weights_ptr, - src_size, + num_subtexels, + inv_num_subtexels, src_samples, - src_samples - src_bilinear_samples); - assert(int(src_samples) - int(num_samples_saved) == src_bilinear_samples); - - // Normalize so that the sum becomes one. Note that we do it twice; - // this sometimes helps a tiny little bit when we have many samples. - for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) { - double sum = 0.0; - for (int i = 0; i < src_bilinear_samples; ++i) { - sum += to_fp64(bilinear_weights_ptr[i].weight); - } - for (int i = 0; i < src_bilinear_samples; ++i) { - bilinear_weights_ptr[i].weight = from_fp64( - to_fp64(bilinear_weights_ptr[i].weight) / sum); - } - } + max_samples_saved); + assert(num_samples_saved == max_samples_saved); + normalize_sum(bilinear_weights_ptr, src_bilinear_samples); } return src_bilinear_samples; } @@ -172,10 +255,10 @@ double compute_sum_sq_error(const Tap* weights, unsigned num_weights, // Find the effective range of the bilinear-optimized kernel. // Due to rounding of the positions, this is not necessarily the same // as the intended range (ie., the range of the original weights). - int lower_pos = int(floor(to_fp64(bilinear_weights[0].pos) * size - 0.5)); - int upper_pos = int(ceil(to_fp64(bilinear_weights[num_bilinear_weights - 1].pos) * size - 0.5)) + 2; + int lower_pos = int(floor(to_fp32(bilinear_weights[0].pos) * size - 0.5)); + int upper_pos = int(ceil(to_fp32(bilinear_weights[num_bilinear_weights - 1].pos) * size - 0.5)) + 2; lower_pos = min(lower_pos, lrintf(weights[0].pos * size - 0.5)); - upper_pos = max(upper_pos, lrintf(weights[num_weights - 1].pos * size - 0.5)); + upper_pos = max(upper_pos, lrintf(weights[num_weights - 1].pos * size - 0.5) + 1); float* effective_weights = new float[upper_pos - lower_pos]; for (int i = 0; i < upper_pos - lower_pos; ++i) { @@ -184,7 +267,7 @@ double compute_sum_sq_error(const Tap* weights, unsigned num_weights, // Now find the effective weights that result from this sampling. for (unsigned i = 0; i < num_bilinear_weights; ++i) { - const float pixel_pos = to_fp64(bilinear_weights[i].pos) * size - 0.5f; + const float pixel_pos = to_fp32(bilinear_weights[i].pos) * size - 0.5f; const int x0 = int(floor(pixel_pos)) - lower_pos; const int x1 = x0 + 1; const float f = lrintf((pixel_pos - (x0 + lower_pos)) / movit_texel_subpixel_precision) * movit_texel_subpixel_precision; @@ -194,8 +277,8 @@ double compute_sum_sq_error(const Tap* weights, unsigned num_weights, assert(x0 < upper_pos - lower_pos); assert(x1 < upper_pos - lower_pos); - effective_weights[x0] += to_fp64(bilinear_weights[i].weight) * (1.0 - f); - effective_weights[x1] += to_fp64(bilinear_weights[i].weight) * f; + effective_weights[x0] += to_fp32(bilinear_weights[i].weight) * (1.0 - f); + effective_weights[x1] += to_fp32(bilinear_weights[i].weight) * f; } // Subtract the desired weights to get the error. @@ -357,7 +440,8 @@ SingleResamplePassEffect::SingleResamplePassEffect(ResampleEffect *parent) last_output_width(-1), last_output_height(-1), last_offset(0.0 / 0.0), // NaN. - last_zoom(0.0 / 0.0) // NaN. + last_zoom(0.0 / 0.0), // NaN. + last_texture_width(-1), last_texture_height(-1) { register_int("direction", (int *)&direction); register_int("input_width", &input_width); @@ -366,8 +450,21 @@ SingleResamplePassEffect::SingleResamplePassEffect(ResampleEffect *parent) register_int("output_height", &output_height); register_float("offset", &offset); register_float("zoom", &zoom); + register_uniform_sampler2d("sample_tex", &uniform_sample_tex); + register_uniform_int("num_samples", &uniform_num_samples); + register_uniform_float("num_loops", &uniform_num_loops); + register_uniform_float("slice_height", &uniform_slice_height); + register_uniform_float("sample_x_scale", &uniform_sample_x_scale); + register_uniform_float("sample_x_offset", &uniform_sample_x_offset); + register_uniform_float("whole_pixel_offset", &uniform_whole_pixel_offset); glGenTextures(1, &texnum); + + if (!lanczos_table_init_done) { + // Could in theory race between two threads if we are unlucky, + // but that is harmless, since they'll write the same data. + init_lanczos_table(); + } } SingleResamplePassEffect::~SingleResamplePassEffect() @@ -494,7 +591,7 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str // Now sample pixels on each side around that point. for (int i = 0; i < src_samples; ++i) { int src_y = base_src_y + i - int_radius; - float weight = lanczos_weight(radius_scaling_factor * (src_y - center_src_y - subpixel_offset), LANCZOS_RADIUS); + float weight = lanczos_weight_cached(radius_scaling_factor * (src_y - center_src_y - subpixel_offset)); weights[y * src_samples + i].weight = weight * radius_scaling_factor; weights[y * src_samples + i].pos = (src_y + 0.5) / float(src_size); } @@ -502,6 +599,9 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str // Now make use of the bilinear filtering in the GPU to reduce the number of samples // we need to make. Try fp16 first; if it's not accurate enough, we go to fp32. + // Our tolerance level for total error is a bit higher than the one for invididual + // samples, since one would assume overall errors in the shape don't matter as much. + const float max_error = 2.0f / (255.0f * 255.0f); Tap *bilinear_weights_fp16; src_bilinear_samples = combine_many_samples(weights, src_size, src_samples, dst_samples, &bilinear_weights_fp16); Tap *bilinear_weights_fp32 = NULL; @@ -513,11 +613,12 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str bilinear_weights_fp16 + y * src_bilinear_samples, src_bilinear_samples, src_size); max_sum_sq_error_fp16 = std::max(max_sum_sq_error_fp16, sum_sq_error_fp16); + if (max_sum_sq_error_fp16 > max_error) { + break; + } } - // Our tolerance level for total error is a bit higher than the one for invididual - // samples, since one would assume overall errors in the shape don't matter as much. - if (max_sum_sq_error_fp16 > 2.0f / (255.0f * 255.0f)) { + if (max_sum_sq_error_fp16 > max_error) { fallback_to_fp32 = true; src_bilinear_samples = combine_many_samples(weights, src_size, src_samples, dst_samples, &bilinear_weights_fp32); } @@ -527,16 +628,39 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const str check_error(); glBindTexture(GL_TEXTURE_2D, texnum); check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); - check_error(); + if (last_texture_width == -1) { + // Need to set this state the first time. + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); + check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); + check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); + check_error(); + } + + GLenum type, internal_format; + void *pixels; if (fallback_to_fp32) { - glTexImage2D(GL_TEXTURE_2D, 0, GL_RG32F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_FLOAT, bilinear_weights_fp32); + type = GL_FLOAT; + internal_format = GL_RG32F; + pixels = bilinear_weights_fp32; } else { - glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_HALF_FLOAT, bilinear_weights_fp16); + type = GL_HALF_FLOAT; + internal_format = GL_RG16F; + pixels = bilinear_weights_fp16; + } + + if (int(src_bilinear_samples) == last_texture_width && + int(dst_samples) == last_texture_height && + internal_format == last_texture_internal_format) { + // Texture dimensions and type are unchanged; it is more efficient + // to just update it rather than making an entirely new texture. + glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, src_bilinear_samples, dst_samples, GL_RG, type, pixels); + } else { + glTexImage2D(GL_TEXTURE_2D, 0, internal_format, src_bilinear_samples, dst_samples, 0, GL_RG, type, pixels); + last_texture_width = src_bilinear_samples; + last_texture_height = dst_samples; + last_texture_internal_format = internal_format; } check_error(); @@ -574,31 +698,31 @@ void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const strin glBindTexture(GL_TEXTURE_2D, texnum); check_error(); - set_uniform_int(glsl_program_num, prefix, "sample_tex", *sampler_num); + uniform_sample_tex = *sampler_num; ++*sampler_num; - set_uniform_int(glsl_program_num, prefix, "num_samples", src_bilinear_samples); - set_uniform_float(glsl_program_num, prefix, "num_loops", num_loops); - set_uniform_float(glsl_program_num, prefix, "slice_height", slice_height); + uniform_num_samples = src_bilinear_samples; + uniform_num_loops = num_loops; + uniform_slice_height = slice_height; // Instructions for how to convert integer sample numbers to positions in the weight texture. - set_uniform_float(glsl_program_num, prefix, "sample_x_scale", 1.0f / src_bilinear_samples); - set_uniform_float(glsl_program_num, prefix, "sample_x_offset", 0.5f / src_bilinear_samples); + uniform_sample_x_scale = 1.0f / src_bilinear_samples; + uniform_sample_x_offset = 0.5f / src_bilinear_samples; - float whole_pixel_offset; if (direction == SingleResamplePassEffect::VERTICAL) { - whole_pixel_offset = lrintf(offset) / float(input_height); + uniform_whole_pixel_offset = lrintf(offset) / float(input_height); } else { - whole_pixel_offset = lrintf(offset) / float(input_width); + uniform_whole_pixel_offset = lrintf(offset) / float(input_width); } - set_uniform_float(glsl_program_num, prefix, "whole_pixel_offset", whole_pixel_offset); // We specifically do not want mipmaps on the input texture; // they break minification. Node *self = chain->find_node_for_effect(this); - glActiveTexture(chain->get_input_sampler(self, 0)); - check_error(); - glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); - check_error(); + if (chain->has_input_sampler(self, 0)) { + glActiveTexture(chain->get_input_sampler(self, 0)); + check_error(); + glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); + check_error(); + } } } // namespace movit