X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=resample_effect.cpp;h=50b7c6bc5c4730fc6bb25cd18c96a446c8f02986;hp=c0e82f1cb7c757088e2036b78a8d2ea1a34637c2;hb=refs%2Fheads%2Fepoxy;hpb=fb92a4e217a92ecf83b7812cc6933f6f3048b752 diff --git a/resample_effect.cpp b/resample_effect.cpp index c0e82f1..50b7c6b 100644 --- a/resample_effect.cpp +++ b/resample_effect.cpp @@ -1,13 +1,22 @@ // Three-lobed Lanczos, the most common choice. #define LANCZOS_RADIUS 3.0 -#include +#include #include +#include +#include +#include +#include -#include "resample_effect.h" #include "effect_chain.h" +#include "effect_util.h" +#include "fp16.h" +#include "resample_effect.h" #include "util.h" -#include "opengl.h" + +using namespace std; + +namespace movit { namespace { @@ -29,6 +38,72 @@ float lanczos_weight(float x, float a) } } +// Euclid's algorithm, from Wikipedia. +unsigned gcd(unsigned a, unsigned b) +{ + while (b != 0) { + unsigned t = b; + b = a % b; + a = t; + } + return a; +} + +unsigned combine_samples(float *src, float *dst, unsigned num_src_samples, unsigned max_samples_saved) +{ + unsigned num_samples_saved = 0; + 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) { + dst[j * 2 + 0] = src[i * 2 + 0]; + dst[j * 2 + 1] = src[i * 2 + 1]; + } + + if (i == num_src_samples - 1) { + // Last sample; cannot combine. + continue; + } + assert(num_samples_saved <= max_samples_saved); + if (num_samples_saved == max_samples_saved) { + // We could maybe save more here, but other rows can't, so don't bother. + continue; + } + + float w1 = src[i * 2 + 0]; + float w2 = src[(i + 1) * 2 + 0]; + if (w1 * w2 < 0.0f) { + // Differing signs; cannot combine. + continue; + } + + float pos1 = src[i * 2 + 1]; + float pos2 = src[(i + 1) * 2 + 1]; + assert(pos2 > pos1); + + float offset, total_weight, sum_sq_error; + combine_two_samples(w1, w2, &offset, &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, + // but since the artifacts are not really random, they can get quite + // visible. On the other hand, going to 0.25f, I can see no change at + // all with 8-bit output, so it would not seem to be worth it.) + if (sum_sq_error > 0.5f / (256.0f * 256.0f)) { + continue; + } + + // OK, we can combine this and the next sample. + if (dst != NULL) { + dst[j * 2 + 0] = total_weight; + dst[j * 2 + 1] = pos1 + offset * (pos2 - pos1); + } + + ++i; // Skip the next sample. + ++num_samples_saved; + } + return num_samples_saved; +} + } // namespace ResampleEffect::ResampleEffect() @@ -40,9 +115,9 @@ ResampleEffect::ResampleEffect() // The first blur pass will forward resolution information to us. hpass = new SingleResamplePassEffect(this); - hpass->set_int("direction", SingleResamplePassEffect::HORIZONTAL); + CHECK(hpass->set_int("direction", SingleResamplePassEffect::HORIZONTAL)); vpass = new SingleResamplePassEffect(NULL); - vpass->set_int("direction", SingleResamplePassEffect::VERTICAL); + CHECK(vpass->set_int("direction", SingleResamplePassEffect::VERTICAL)); update_size(); } @@ -68,7 +143,7 @@ void ResampleEffect::inform_input_size(unsigned input_num, unsigned width, unsig input_height = height; update_size(); } - + void ResampleEffect::update_size() { bool ok = true; @@ -85,7 +160,7 @@ void ResampleEffect::update_size() assert(ok); } -bool ResampleEffect::set_float(const std::string &key, float value) { +bool ResampleEffect::set_float(const string &key, float value) { if (key == "width") { output_width = value; update_size(); @@ -123,7 +198,7 @@ SingleResamplePassEffect::~SingleResamplePassEffect() glDeleteTextures(1, &texnum); } -std::string SingleResamplePassEffect::output_fragment_shader() +string SingleResamplePassEffect::output_fragment_shader() { char buf[256]; sprintf(buf, "#define DIRECTION_VERTICAL %d\n", (direction == VERTICAL)); @@ -141,11 +216,8 @@ std::string SingleResamplePassEffect::output_fragment_shader() // so out[0] will read from parameters = <0,0>, <1,0>, <2,0> and so on. // // For horizontal scaling, we fill in the exact same texture; -// the shader just interprets is differently. -// -// TODO: Support optimization of wrapping the sample texture. -// TODO: Support optimization using free linear sampling, like in BlurEffect. -void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) +// the shader just interprets it differently. +void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num) { unsigned src_size, dst_size; if (direction == SingleResamplePassEffect::HORIZONTAL) { @@ -160,6 +232,15 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std assert(false); } + // For many resamplings (e.g. 640 -> 1280), we will end up with the same + // set of samples over and over again in a loop. Thus, we can compute only + // the first such loop, and then ask the card to repeat the texture for us. + // This is both easier on the texture cache and lowers our CPU cost for + // generating the kernel somewhat. + num_loops = gcd(src_size, dst_size); + slice_height = 1.0f / num_loops; + unsigned dst_samples = dst_size / num_loops; + // Sample the kernel in the right place. A diagram with a triangular kernel // (corresponding to linear filtering, and obviously with radius 1) // for easier ASCII art drawing: @@ -209,11 +290,11 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std // Anyhow, in this case we clearly need to look at more source pixels // to compute the destination pixel, and how many depend on the scaling factor. // Thus, the kernel width will vary with how much we scale. - float radius_scaling_factor = std::min(float(dst_size) / float(src_size), 1.0f); + float radius_scaling_factor = min(float(dst_size) / float(src_size), 1.0f); int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor); - src_samples = int_radius * 2 + 1; - float *weights = new float[dst_size * src_samples * 2]; - for (unsigned y = 0; y < dst_size; ++y) { + int src_samples = int_radius * 2 + 1; + float *weights = new float[dst_samples * src_samples * 2]; + for (unsigned y = 0; y < dst_samples; ++y) { // Find the point around which we want to sample the source image, // compensating for differing pixel centers as the scale changes. float center_src_y = (y + 0.5f) * float(src_size) / float(dst_size) - 0.5f; @@ -226,10 +307,57 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std weights[(y * src_samples + i) * 2 + 0] = weight * radius_scaling_factor; weights[(y * src_samples + i) * 2 + 1] = (src_y + 0.5) / float(src_size); } + } - // Encode as a two-component texture. Note the GL_REPEAT, which is not relevant - // right now, but will be later. + // Now 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 + // figure out the maximum number of samples. Then, we downconvert all the weights to + // that number -- we could have gone for a variable-length system, but this is simpler, + // and the gains would probably be offset by the extra cost of checking when to stop. + // + // The greedy strategy for combining samples is optimal. + src_bilinear_samples = 0; + for (unsigned y = 0; y < dst_samples; ++y) { + unsigned num_samples_saved = combine_samples(weights + (y * src_samples) * 2, NULL, src_samples, UINT_MAX); + src_bilinear_samples = max(src_bilinear_samples, src_samples - num_samples_saved); + } + + // Now that we know the right width, actually combine the samples. + float *bilinear_weights = new float[dst_samples * src_bilinear_samples * 2]; + fp16_int_t *bilinear_weights_fp16 = new fp16_int_t[dst_samples * src_bilinear_samples * 2]; + for (unsigned y = 0; y < dst_samples; ++y) { + float *bilinear_weights_ptr = bilinear_weights + (y * src_bilinear_samples) * 2; + fp16_int_t *bilinear_weights_fp16_ptr = bilinear_weights_fp16 + (y * src_bilinear_samples) * 2; + unsigned num_samples_saved = combine_samples( + weights + (y * src_samples) * 2, + bilinear_weights_ptr, + src_samples, + src_samples - src_bilinear_samples); + assert(int(src_samples) - int(num_samples_saved) == src_bilinear_samples); + + // Convert to fp16. + for (int i = 0; i < src_bilinear_samples; ++i) { + bilinear_weights_fp16_ptr[i * 2 + 0] = fp64_to_fp16(bilinear_weights_ptr[i * 2 + 0]); + bilinear_weights_fp16_ptr[i * 2 + 1] = fp64_to_fp16(bilinear_weights_ptr[i * 2 + 1]); + } + + // 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 += fp16_to_fp64(bilinear_weights_fp16_ptr[i * 2 + 0]); + } + for (int i = 0; i < src_bilinear_samples; ++i) { + bilinear_weights_fp16_ptr[i * 2 + 0] = fp64_to_fp16( + fp16_to_fp64(bilinear_weights_fp16_ptr[i * 2 + 0]) / sum); + } + } + } + + // Encode as a two-component texture. Note the GL_REPEAT. glActiveTexture(GL_TEXTURE0 + *sampler_num); check_error(); glBindTexture(GL_TEXTURE_2D, texnum); @@ -240,17 +368,23 @@ void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const std check_error(); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); check_error(); - glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_samples, dst_size, 0, GL_RG, GL_FLOAT, weights); + glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_HALF_FLOAT, bilinear_weights_fp16); check_error(); delete[] weights; - + delete[] bilinear_weights; + delete[] bilinear_weights_fp16; } -void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num) +void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num) { Effect::set_gl_state(glsl_program_num, prefix, sampler_num); + assert(input_width > 0); + assert(input_height > 0); + assert(output_width > 0); + assert(output_height > 0); + if (input_width != last_input_width || input_height != last_input_height || output_width != last_output_width || @@ -269,16 +403,21 @@ void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const std:: set_uniform_int(glsl_program_num, prefix, "sample_tex", *sampler_num); ++sampler_num; - set_uniform_int(glsl_program_num, prefix, "num_samples", src_samples); + 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); // 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_samples); - set_uniform_float(glsl_program_num, prefix, "sample_x_offset", 0.5f / src_samples); + 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); // We specifically do not want mipmaps on the input texture; // they break minification. - glActiveTexture(GL_TEXTURE0); + 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(); } + +} // namespace movit