Class: SPCore::HybridResampling
- Inherits:
-
Object
- Object
- SPCore::HybridResampling
- Defined in:
- lib/spcore/resampling/hybrid_resampling.rb
Overview
for downsampling.
Class Method Summary collapse
Class Method Details
.resample(input, sample_rate, upsample_factor, downsample_factor, filter_order) ⇒ Object
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 |
# File 'lib/spcore/resampling/hybrid_resampling.rb', line 5 def self.resample input, sample_rate, upsample_factor, downsample_factor, filter_order raise ArgumentError, "input.size is less than four" unless input.size >= 4 raise ArgumentError, "upsample_factor is not greater than 1" unless upsample_factor > 1 raise ArgumentError, "downsample_factor is not a Fixnum" unless downsample_factor.is_a?(Fixnum) raise ArgumentError, "downsample_factor is not greater than 1" unless downsample_factor > 1 raise ArgumentError, "sample_rate is not greater than 0" unless sample_rate > 0 upsampled = PolynomialResampling.upsample input, upsample_factor needed_samples = upsampled.size % downsample_factor if needed_samples == 0 upsampled += Array.new(needed_samples, 0.0) end target_rate = sample_rate * upsample_factor / downsample_factor cutoff = (target_rate < sample_rate) ? (target_rate / 2.0) : (sample_rate / 2.0) filter = SincFilter.new( :sample_rate => (sample_rate * upsample_factor), :order => filter_order, :cutoff_freq => cutoff, :window_class => NuttallWindow ) filtered = filter.lowpass(upsampled) return Array.new(filtered.size / downsample_factor){ |i| filtered[i * downsample_factor] } end |