#include "effect_chain.h"
#include "effect_util.h"
#include "fp16.h"
+#include "init.h"
#include "resample_effect.h"
#include "util.h"
}
template<class DestFloat>
-unsigned combine_samples(Tap<float> *src, Tap<DestFloat> *dst, unsigned src_size, unsigned num_src_samples, unsigned max_samples_saved)
+unsigned combine_samples(const Tap<float> *src, Tap<DestFloat> *dst, unsigned src_size, 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) {
// 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)) {
+ if (sum_sq_error > 0.5f / (255.0f * 255.0f)) {
continue;
}
return num_samples_saved;
}
+// 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.
+template<class DestFloat>
+unsigned combine_many_samples(const Tap<float> *weights, unsigned src_size, unsigned src_samples, unsigned dst_samples, Tap<DestFloat> **bilinear_weights)
+{
+ int src_bilinear_samples = 0;
+ for (unsigned y = 0; y < dst_samples; ++y) {
+ unsigned num_samples_saved = combine_samples<DestFloat>(weights + y * src_samples, NULL, src_size, src_samples, UINT_MAX);
+ src_bilinear_samples = max<int>(src_bilinear_samples, src_samples - num_samples_saved);
+ }
+
+ // Now that we know the right width, actually combine the samples.
+ *bilinear_weights = new Tap<DestFloat>[dst_samples * src_bilinear_samples];
+ for (unsigned y = 0; y < dst_samples; ++y) {
+ Tap<DestFloat> *bilinear_weights_ptr = *bilinear_weights + y * src_bilinear_samples;
+ unsigned num_samples_saved = combine_samples(
+ weights + y * src_samples,
+ bilinear_weights_ptr,
+ src_size,
+ 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<DestFloat>(
+ to_fp64(bilinear_weights_ptr[i].weight) / sum);
+ }
+ }
+ }
+ return src_bilinear_samples;
+}
+
+// Compute the sum of squared errors between the ideal weights (which are
+// assumed to fall exactly on pixel centers) and the weights that result
+// from sampling at <bilinear_weights>. The primary reason for the difference
+// is inaccuracy in the sampling positions, both due to limited precision
+// in storing them (already inherent in sending them in as fp16_int_t)
+// and in subtexel sampling precision (which we calculate in this function).
+template<class T>
+double compute_sum_sq_error(const Tap<float>* weights, unsigned num_weights,
+ const Tap<T>* bilinear_weights, unsigned num_bilinear_weights,
+ unsigned size)
+{
+ // 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;
+ lower_pos = min<int>(lower_pos, lrintf(weights[0].pos * size - 0.5));
+ upper_pos = max<int>(upper_pos, lrintf(weights[num_weights - 1].pos * size - 0.5));
+
+ float* effective_weights = new float[upper_pos - lower_pos];
+ for (int i = 0; i < upper_pos - lower_pos; ++i) {
+ effective_weights[i] = 0.0f;
+ }
+
+ // 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 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;
+
+ assert(x0 >= 0);
+ assert(x1 >= 0);
+ 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;
+ }
+
+ // Subtract the desired weights to get the error.
+ for (unsigned i = 0; i < num_weights; ++i) {
+ const int x = lrintf(weights[i].pos * size - 0.5f) - lower_pos;
+ assert(x >= 0);
+ assert(x < upper_pos - lower_pos);
+
+ effective_weights[x] -= weights[i].weight;
+ }
+
+ double sum_sq_error = 0.0;
+ for (unsigned i = 0; i < num_weights; ++i) {
+ sum_sq_error += effective_weights[i] * effective_weights[i];
+ }
+
+ delete[] effective_weights;
+ return sum_sq_error;
+}
+
} // namespace
ResampleEffect::ResampleEffect()
}
// 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;
+ // we need to make. Try fp16 first; if it's not accurate enough, we go to fp32.
+ Tap<fp16_int_t> *bilinear_weights_fp16;
+ src_bilinear_samples = combine_many_samples(weights, src_size, src_samples, dst_samples, &bilinear_weights_fp16);
+ Tap<float> *bilinear_weights_fp32 = NULL;
+ bool fallback_to_fp32 = false;
+ double max_sum_sq_error_fp16 = 0.0;
for (unsigned y = 0; y < dst_samples; ++y) {
- unsigned num_samples_saved = combine_samples<fp16_int_t>(weights + y * src_samples, NULL, src_size, src_samples, UINT_MAX);
- src_bilinear_samples = max<int>(src_bilinear_samples, src_samples - num_samples_saved);
+ double sum_sq_error_fp16 = compute_sum_sq_error(
+ weights + y * src_samples, src_samples,
+ 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);
}
- // Now that we know the right width, actually combine the samples.
- Tap<fp16_int_t> *bilinear_weights = new Tap<fp16_int_t>[dst_samples * src_bilinear_samples];
- for (unsigned y = 0; y < dst_samples; ++y) {
- Tap<fp16_int_t> *bilinear_weights_ptr = bilinear_weights + y * src_bilinear_samples;
- unsigned num_samples_saved = combine_samples(
- weights + y * src_samples,
- bilinear_weights_ptr,
- src_size,
- 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 += fp16_to_fp64(bilinear_weights_ptr[i].weight);
- }
- for (int i = 0; i < src_bilinear_samples; ++i) {
- bilinear_weights_ptr[i].weight = fp64_to_fp16(
- fp16_to_fp64(bilinear_weights_ptr[i].weight) / sum);
- }
- }
+ // 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)) {
+ fallback_to_fp32 = true;
+ src_bilinear_samples = combine_many_samples(weights, src_size, src_samples, dst_samples, &bilinear_weights_fp32);
}
// Encode as a two-component texture. Note the GL_REPEAT.
check_error();
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
check_error();
- glTexImage2D(GL_TEXTURE_2D, 0, GL_RG16F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_HALF_FLOAT, bilinear_weights);
+ if (fallback_to_fp32) {
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_RG32F, src_bilinear_samples, dst_samples, 0, GL_RG, GL_FLOAT, 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);
+ }
check_error();
delete[] weights;
- delete[] bilinear_weights;
+ delete[] bilinear_weights_fp16;
+ delete[] bilinear_weights_fp32;
}
void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
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