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Add anti-alias filtering just in case

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Cap the output bandwidth to 92%.
Even at 48kHz it still translates to 100% source bandwidth.
This just provides a little bit of anti-alias filtering.
There is more then likely nothing there to filter,
but it doesn't hurt or cost us anything to make sure.
This commit is contained in:
JasonLG1979 2023-07-02 17:59:11 -05:00
parent 74e3f938da
commit 87bbd539b7
1 changed files with 11 additions and 1 deletions
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12
playback/src/config.rs
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@ -19,11 +19,20 @@ const HZ96000_SAMPLES_PER_SECOND: f64 = 96_000.0 * 2.0;
// which translates to much better interpolation.
const HZ48000_INTERPOLATION_OUTPUT_SIZE: usize =
(RESAMPLER_INPUT_SIZE as f64 * (1.0 / HZ48000_RESAMPLE_FACTOR_RECIPROCAL)) as usize;
const HZ88200_INTERPOLATION_OUTPUT_SIZE: usize =
(RESAMPLER_INPUT_SIZE as f64 * (1.0 / HZ88200_RESAMPLE_FACTOR_RECIPROCAL)) as usize;
const HZ96000_INTERPOLATION_OUTPUT_SIZE: usize =
(RESAMPLER_INPUT_SIZE as f64 * (1.0 / HZ96000_RESAMPLE_FACTOR_RECIPROCAL)) as usize;
// This is the bandwidth of the output.
// Even at 48kHz it still translates to 100% source bandwidth.
// This just provides a little bit of anti-alias filtering.
// There is more then likely nothing there to filter,
// but it doesn't hurt or cost us anything to make sure.
const WINDOWED_SINC_INTERPOLATION_BANDWIDTH: f64 = 0.92;
// Blackman Window coefficients
const BLACKMAN_A0: f64 = 0.42;
const BLACKMAN_A1: f64 = 0.5;
@ -89,7 +98,8 @@ impl InterpolationQuality {
|interpolation_coefficient_index| {
let index_float = interpolation_coefficient_index as f64;
let sample_index_fractional = (index_float * resample_factor_reciprocal).fract();
let sinc_center_offset = index_float - sinc_center;
let sinc_center_offset =
(index_float - sinc_center) * WINDOWED_SINC_INTERPOLATION_BANDWIDTH;
let sample_index_fractional_sinc_weight = Self::sinc(sample_index_fractional);