Function SampleAverageLuma

tests/FFmpegReader.cpp:37–60

namespace {

double SampleAverageLuma(const std::shared_ptr<Frame>& frame, int sample_grid = 4) {
	const int width = frame->GetWidth();
	const int height = frame->GetHeight();
	if (width <= 0 || height <= 0) {
		return 0.0;
	}

	int64_t luma_sum = 0;
	int64_t sample_count = 0;
	for (int y = 0; y < sample_grid; ++y) {
		const int row = std::min(height - 1, (y * height) / sample_grid);
		const unsigned char* pixels = frame->GetPixels(row);
		for (int x = 0; x < sample_grid; ++x) {
			const int col = std::min(width - 1, (x * width) / sample_grid);
			const int pixel_index = col * 4;
			luma_sum += (pixels[pixel_index] + pixels[pixel_index + 1] + pixels[pixel_index + 2]) / 3;
			++sample_count;
		}
	}

	return sample_count > 0
		? static_cast<double>(luma_sum) / static_cast<double>(sample_count)
		: 0.0;
}

struct HardwareDecoderSettingsGuard {
	int decoder = 0;