From f7b3bd919838baee43524a227b82dff3aae31d74 Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Sun, 6 Mar 2022 15:17:22 +0100
Subject: [PATCH] Add gain compensation to the STFT helper
---
src/util/stft.rs | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)
diff --git a/src/util/stft.rs b/src/util/stft.rs
index 8be4d78e..ff209f1a 100644
--- a/src/util/stft.rs
+++ b/src/util/stft.rs
@@ -92,12 +92,13 @@ impl<const NUM_SIDECHAIN_INPUTS: usize> StftHelper<NUM_SIDECHAIN_INPUTS> {
/// Process the audio in `main_buffer` and in any sidechain buffers in small overlapping blocks
/// with a window function applied, adding up the results for the main buffer so they can be
- /// written back to the host. Whenever a new block is available, `process_cb()` gets called with
- /// a new audio block of the specified size with the windowing function already applied. The
- /// summed reults will then be written back to `main_buffer` exactly one block later, which
- /// means that this function will introduce one block of latency. This can be compensated by
- /// calling [`ProcessContext::set_latency()`][`crate::prelude::ProcessContext::set_latency()`]
- /// in your plugin's initialization function.
+ /// written back to the host. The window overlap amount is compensated automatically when adding
+ /// up these samples. Whenever a new block is available, `process_cb()` gets called with a new
+ /// audio block of the specified size with the windowing function already applied. The summed
+ /// reults will then be written back to `main_buffer` exactly one block later, which means that
+ /// this function will introduce one block of latency. This can be compensated by calling
+ /// [`ProcessContext::set_latency()`][`crate::prelude::ProcessContext::set_latency()`] in your
+ /// plugin's initialization function.
///
/// For efficiency's sake this function will reuse the same vector for all calls to
/// `process_cb`. This means you can only access a single channel's worth of windowed data at a
@@ -119,12 +120,14 @@ impl<const NUM_SIDECHAIN_INPUTS: usize> StftHelper<NUM_SIDECHAIN_INPUTS> {
sidechain_buffers: [&Buffer; NUM_SIDECHAIN_INPUTS],
window_function: &[f32],
overlap_times: usize,
+ overlap_gain_compensation: f32,
mut process_cb: F,
) where
F: FnMut(usize, Option<usize>, &mut [f32]),
{
assert_eq!(main_buffer.channels(), self.main_input_ring_buffers.len());
assert_eq!(window_function.len(), self.main_input_ring_buffers[0].len());
+ assert!(overlap_times > 0);
// We'll copy samples from `*_buffer` into `*_ring_buffers` while simultaneously copying
// already processed samples from `main_ring_buffers` in into `main_buffer`
@@ -224,6 +227,7 @@ impl<const NUM_SIDECHAIN_INPUTS: usize> StftHelper<NUM_SIDECHAIN_INPUTS> {
&self.scratch_buffer,
self.current_pos,
output_ring_buffer,
+ overlap_gain_compensation,
);
}
}
@@ -262,7 +266,12 @@ fn multiply_scratch_buffer(scratch_buffer: &mut [f32], window_function: &[f32])
/// Add data from the scratch buffer to the specified ring buffer. When writing samples from this
/// ring buffer back to the host's outputs they must be cleared to prevent infinite feedback.
#[inline]
-fn add_scratch_to_ring_buffer(scratch_buffer: &[f32], current_pos: usize, ring_buffer: &mut [f32]) {
+fn add_scratch_to_ring_buffer(
+ scratch_buffer: &[f32],
+ current_pos: usize,
+ ring_buffer: &mut [f32],
+ gain_compensation: f32,
+) {
// TODO: This could also use some SIMD
let block_size = scratch_buffer.len();
let num_copy_before_wrap = block_size - current_pos;
@@ -270,12 +279,14 @@ fn add_scratch_to_ring_buffer(scratch_buffer: &[f32], current_pos: usize, ring_b
.iter()
.zip(&mut ring_buffer[current_pos..block_size])
{
- *ring_sample += *scratch_sample;
+ // TODO: Moving this gain compensation to the window is more efficient, but that makes the
+ // interface less nice to work with
+ *ring_sample += *scratch_sample * gain_compensation;
}
for (scratch_sample, ring_sample) in scratch_buffer[num_copy_before_wrap..block_size]
.iter()
.zip(&mut ring_buffer[0..current_pos])
{
- *ring_sample += *scratch_sample;
+ *ring_sample += *scratch_sample * gain_compensation;
}
}