Waveform bar geometry

Linear: AUT-105

Maps an AudioHistogram to a list of axis-aligned rectangles that wisp's graphics pipeline can render directly.

api

Data flow

sequenceDiagram
    participant Src as AudioChunk source
    participant Hist as histogram::quantize
    participant Geom as waveform::mono_bars / stereo_bars
    participant Wisp as wisp::Graphics

    Src->>Hist: AudioChunk (PTS, samples)
    Hist->>Geom: AudioHistogram (peak + rms per bucket)
    Geom->>Wisp: Vec<WaveformBarRect>
    Wisp->>Wisp: graphics.rect(x, y, w, h) per bar

The histogram carries timing on a media timeline (each bar has start_time + duration); the geometry stage drops timing and lays bars out by index, with bar_width + bar_gap between adjacent left edges. Timeline-aligned layout (dope-sheet, scrubber) is the caller's job — this module is unit-agnostic.

Coordinate convention

Rectangles use a y-up convention (matching wisp NDC): x / y is the bottom-left corner, width / height are non-negative. Layout values use whatever unit the caller picks — NDC [-1, +1], screen pixels, normalized [0, 1]. The math doesn't care.

Two display modes

Quick start

#![allow(unused)]
fn main() {
use media::{
    audio::AudioFormat, clock::MediaDuration, histogram::quantize,
    mock_audio::SineWaveSource, waveform::{mono_bars, WaveformLayout},
};

let mut src = SineWaveSource::new(AudioFormat::mono_f32(48_000), 440.0, 0.6);
let chunk = src.next_chunk(48_000);                       // 1 s
let h = quantize(&chunk, MediaDuration::from_millis(50)); // 20 bars
let rects = mono_bars(&h, &WaveformLayout::ndc_default());
// rects.len() == 20; each rect.height == bar.peak * 0.4
}

Manual regression — four-bar table

A test crafts a 4-bar histogram with peak = [1.0, 0.5, 0.25, 0.0], lays it out anchored at y = 0, bar_width = 0.1, bar_gap = 0.02, max_height = 1.0, origin_x = 0.0. Expected geometry:

Stride = bar_width + bar_gap = 0.12. Height = peak × max_height. The bar-4 zero-height rect is preserved (geometry stays parallel to histogram order) so downstream renderers can use stable indices.

Next

Render synthetic audio histogram in Wisp takes this geometry list and draws it through wisp::Graphics for the first time.