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//! Circular buffer for real-time waveform visualization.
//!
//! This module provides efficient storage for audio samples used in the oscilloscope
//! display. It maintains a fixed-size circular buffer that automatically discards
//! old samples as new ones arrive, providing a sliding window view of the audio
//! waveform suitable for real-time visualization.
//!
//! Also supports vectorscope visualization by storing stereo sample pairs.
use std::collections::VecDeque;
/// A stereo sample pair (left, right)
#[derive(Clone, Copy, Debug)]
pub struct StereoSample {
pub left: f32,
pub right: f32,
}
pub struct WaveformBuffer {
samples: VecDeque<f32>,
stereo_samples: VecDeque<StereoSample>, // For vectorscope
max_samples: usize,
}
impl WaveformBuffer {
pub fn new(max_samples: usize) -> Self {
Self {
samples: VecDeque::with_capacity(max_samples),
stereo_samples: VecDeque::with_capacity(max_samples),
max_samples,
}
}
/// Push mono samples (or mixed-down stereo) for oscilloscope display
pub fn push_samples(&mut self, new_samples: &[f32]) {
for &sample in new_samples {
self.samples.push_back(sample);
// Keep only the most recent samples
while self.samples.len() > self.max_samples {
self.samples.pop_front();
}
}
}
/// Push interleaved stereo samples for both oscilloscope and vectorscope
/// Samples should be in [L, R, L, R, ...] format
pub fn push_stereo_samples(&mut self, new_samples: &[f32]) {
// Push to mono buffer (mixed down for oscilloscope)
for chunk in new_samples.chunks(2) {
if chunk.len() == 2 {
let mixed = (chunk[0] + chunk[1]) / 2.0;
self.samples.push_back(mixed);
while self.samples.len() > self.max_samples {
self.samples.pop_front();
}
// Also store as stereo pair for vectorscope
self.stereo_samples.push_back(StereoSample {
left: chunk[0],
right: chunk[1],
});
while self.stereo_samples.len() > self.max_samples {
self.stereo_samples.pop_front();
}
}
}
}
/// Get stereo sample pairs for vectorscope display
/// Returns up to `count` most recent (left, right) pairs with amplification
pub fn get_vectorscope_points(&self, count: usize) -> Vec<(f64, f64)> {
// Amplification factor to spread out the display
// Most recordings have moderate levels, so boost to fill the scope
const VECTORSCOPE_GAIN: f64 = 2.5;
if self.stereo_samples.is_empty() {
return vec![];
}
// Downsample if we have more samples than requested
let total = self.stereo_samples.len();
let step = (total as f32 / count as f32).max(1.0);
(0..count.min(total))
.map(|i| {
let idx = (i as f32 * step) as usize;
if let Some(sample) = self.stereo_samples.get(idx) {
// Apply gain and clamp to display bounds
let left = (sample.left as f64 * VECTORSCOPE_GAIN).clamp(-0.98, 0.98);
let right = (sample.right as f64 * VECTORSCOPE_GAIN).clamp(-0.98, 0.98);
(left, right)
} else {
(0.0, 0.0)
}
})
.collect()
}
/// Get min/max pairs for peak-to-peak display without trigger stabilization.
/// This provides better waveform visualization by showing the envelope.
/// Use `get_triggered_display_peaks` for a stable oscilloscope view.
#[allow(dead_code)]
pub fn get_display_peaks(&self, count: usize) -> Vec<(f32, f32)> {
self.get_peaks_from_offset(count, 0)
}
/// Get min/max pairs starting from a trigger point for stable oscilloscope display.
/// Uses rising-edge zero-crossing detection to align the waveform consistently.
pub fn get_triggered_display_peaks(&self, count: usize) -> Vec<(f32, f32)> {
let trigger_offset = self.find_trigger_offset();
self.get_peaks_from_offset(count, trigger_offset)
}
/// Find a rising-edge zero-crossing point to use as trigger.
/// Searches the first portion of the buffer for a point where the signal
/// crosses from negative to non-negative (rising edge at zero).
fn find_trigger_offset(&self) -> usize {
if self.samples.len() < 2 {
return 0;
}
// Search the first quarter of the buffer for a trigger point
// This leaves enough samples after the trigger for display
let search_range = (self.samples.len() / 4).max(2);
for i in 1..search_range {
let prev = self.samples.get(i - 1).copied().unwrap_or(0.0);
let curr = self.samples.get(i).copied().unwrap_or(0.0);
// Rising edge: previous sample negative, current sample non-negative
if prev < 0.0 && curr >= 0.0 {
return i;
}
}
// No trigger found, return 0 (start from beginning)
0
}
/// Internal helper to get peaks from a given offset in the buffer
fn get_peaks_from_offset(&self, count: usize, offset: usize) -> Vec<(f32, f32)> {
if self.samples.is_empty() || offset >= self.samples.len() {
return vec![(0.0, 0.0); count];
}
// Calculate how many samples we have after the offset
let available_samples = self.samples.len() - offset;
let samples_per_pixel = available_samples as f32 / count as f32;
(0..count)
.map(|i| {
let start_idx = offset + (i as f32 * samples_per_pixel) as usize;
let end_idx = offset + ((i + 1) as f32 * samples_per_pixel) as usize;
let end_idx = end_idx.min(self.samples.len());
if start_idx >= self.samples.len() {
return (0.0, 0.0);
}
// Find min and max in this window
if start_idx == end_idx {
// Single sample
let sample = self.samples.get(start_idx).copied().unwrap_or(0.0);
(sample, sample)
} else {
// Multiple samples - find peaks
let mut min = f32::INFINITY;
let mut max = f32::NEG_INFINITY;
for idx in start_idx..end_idx {
if let Some(&sample) = self.samples.get(idx) {
min = min.min(sample);
max = max.max(sample);
}
}
if min.is_infinite() {
(0.0, 0.0)
} else {
(min, max)
}
}
})
.collect()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_waveform_buffer_new() {
let buffer = WaveformBuffer::new(100);
assert_eq!(buffer.samples.len(), 0);
assert_eq!(buffer.max_samples, 100);
}
#[test]
fn test_push_samples() {
let mut buffer = WaveformBuffer::new(5);
buffer.push_samples(&[1.0, 2.0, 3.0]);
assert_eq!(buffer.samples.len(), 3);
buffer.push_samples(&[4.0, 5.0, 6.0]);
assert_eq!(buffer.samples.len(), 5);
// Should maintain max size
let samples: Vec<f32> = buffer.samples.iter().copied().collect();
assert_eq!(samples, vec![2.0, 3.0, 4.0, 5.0, 6.0]);
}
#[test]
fn test_find_trigger_offset_rising_edge() {
let mut buffer = WaveformBuffer::new(100);
// Create a signal with enough samples so the search range covers the zero crossing
// Search range = samples.len() / 4, so we need at least 16 samples to search up to index 4
buffer.push_samples(&[
-0.5, -0.3, -0.1, 0.1, 0.3, 0.5, 0.3, 0.1, -0.1, -0.3, -0.5, -0.3, -0.1, 0.1, 0.3, 0.5,
]);
let offset = buffer.find_trigger_offset();
// Should find the rising edge at index 3 (where -0.1 -> 0.1)
assert_eq!(offset, 3);
}
#[test]
fn test_find_trigger_offset_no_crossing() {
let mut buffer = WaveformBuffer::new(100);
// All positive samples - no zero crossing
buffer.push_samples(&[0.1, 0.2, 0.3, 0.4, 0.5]);
let offset = buffer.find_trigger_offset();
// Should return 0 when no trigger found
assert_eq!(offset, 0);
}
#[test]
fn test_find_trigger_offset_empty() {
let buffer = WaveformBuffer::new(100);
let offset = buffer.find_trigger_offset();
assert_eq!(offset, 0);
}
#[test]
fn test_triggered_display_peaks() {
let mut buffer = WaveformBuffer::new(100);
// Create a signal with a clear zero crossing
buffer.push_samples(&[
-0.8, -0.6, -0.4, -0.2, 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 0.8, 0.6, 0.4, 0.2, 0.0, -0.2,
-0.4, -0.6, -0.8, -1.0,
]);
let peaks = buffer.get_triggered_display_peaks(5);
// Should have 5 peak pairs
assert_eq!(peaks.len(), 5);
// First peak should start from the trigger point, not from -0.8
}
}