effectcraft/crates/render/src/tests/audio_fx.rs

//! Audio effects through the mixdown (the path preview playback and export share).

use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};

use effectcraft_keyframe::{Keyframe, Value};
use effectcraft_project::build::{self, Ids};
use effectcraft_project::{Comp, Footage, FootageKind, ItemId, ItemKind, LayerSource, Project, Solid};
use effectcraft_time::{FrameRate, Tick};

use crate::audio::{MAX_READ, comp_has_audio, footage_peaks, mix_comp, peak_summary};
use crate::{FootageSource, Image};

const SR: u32 = 8000;

/// Synthetic footage audio as a function of source time (seconds) → (L, R).
struct Signal(fn(f64) -> (f32, f32));
impl FootageSource for Signal {
    fn frame(&self, _: ItemId, _: &Footage, _: Tick) -> Option<Arc<Image>> {
        None
    }
    fn audio(&self, _: ItemId, _: &Footage, start: Tick, frames: usize, rate: u32) -> Option<Vec<f32>> {
        let t0 = start.seconds();
        Some(
            (0..frames)
                .flat_map(|i| {
                    let t = t0 + i as f64 / rate as f64;
                    let (l, r) = if (0.0..2.0).contains(&t) { (self.0)(t) } else { (0.0, 0.0) };
                    [l, r]
                })
                .collect(),
        )
    }
}

fn audio_footage() -> Footage {
    Footage {
        path: "x.wav".into(),
        kind: FootageKind::Audio,
        width: 0,
        height: 0,
        pixel_aspect: 1.0,
        frame_rate: FrameRate::new(25, 1),
        native_rate: None,
        duration: Tick::from_seconds_f64(2.0),
        has_video: false,
        has_audio: true,
        alpha: Default::default(),
        premul_color: [0.0; 3],
        loop_count: 1,
        codec: String::new(),
        missing: false,
        sequence: vec![],
        color_profile: None,
        ..Default::default()
    }
}

/// A 2 s comp with one audio layer (in 0, out 1 s) carrying effect `id` with `vals`.
fn comp_with(id: Option<&str>, vals: &[(&str, Value)], solid: bool) -> (Project, ItemId) {
    let mut p = Project::default();
    let comp = Comp::new(64, 64, FrameRate::new(25, 1), Tick::from_seconds_f64(2.0));
    let src = if solid {
        let sid = p.add_item("S", effectcraft_color::Label::Red, None, ItemKind::Solid(Solid { color: [1.0; 3], width: 64, height: 64, pixel_aspect: 1.0 }));
        LayerSource::Solid { item: sid }
    } else {
        LayerSource::Footage { item: p.add_item("x.wav", effectcraft_color::Label::SeaFoam, None, ItemKind::Footage(audio_footage())) }
    };
    let mut l = build::layer(&mut p, &comp, "a", src, (64, 64), None);
    l.out_point = Tick::from_seconds_f64(1.0);
    if let Some(id) = id {
        let spec = effectcraft_effects::find(id).unwrap();
        let mut next = p.next_id;
        let mut g = effectcraft_effects::instantiate(spec, &mut Ids(&mut next), spec.name, [64.0, 64.0]);
        p.next_id = next;
        for (k, v) in vals {
            g.prop_mut(k).unwrap_or_else(|| panic!("{k}")).value = v.clone();
        }
        l.props.sub_mut("effects").unwrap().children.push(g.into());
    }
    let mut comp = comp;
    comp.layers = vec![l].into();
    let cid = p.add_item("C", effectcraft_color::Label::Sandstone, None, ItemKind::Comp(comp.into()));
    (p, cid)
}

fn mix(p: &Project, src: &dyn FootageSource, cid: ItemId, from: f64, frames: usize) -> Vec<f32> {
    mix_comp(p, src, None, cid, Tick::from_seconds_f64(from), frames, SR)
}

fn ramp(t: f64) -> (f32, f32) {
    (t as f32, -(t as f32))
}

fn rms(m: &[f32]) -> f32 {
    (m.iter().map(|v| v * v).sum::<f32>() / m.len() as f32).sqrt()
}

#[test]
fn backwards_reverses_the_layer_span() {
    let (p, cid) = comp_with(Some("ec.audio.backwards"), &[], false);
    let m = mix(&p, &Signal(ramp), cid, 0.0, SR as usize);
    // Comp time t plays source time ≈ 1 − t.
    for i in [0usize, 2000, 4000, 7999] {
        let t = i as f64 / SR as f64;
        assert!((m[i * 2] as f64 - (1.0 - t)).abs() < 2.0 / SR as f64, "i={i}: {}", m[i * 2]);
    }
    let (p, cid) = comp_with(None, &[], false);
    let m = mix(&p, &Signal(ramp), cid, 0.0, SR as usize);
    assert!((m[4000 * 2] - 0.5).abs() < 1e-3);
}

/// `comp_with`, its layer reversed at `stretch` (< 0) the way After Effects lays it out: in 0,
/// out `out` s, starting at the out point.
fn reversed(id: Option<&str>, vals: &[(&str, Value)], solid: bool, stretch: f64, out: f64) -> (Project, ItemId) {
    let (mut p, cid) = comp_with(id, vals, solid);
    let l = &mut p.comp_mut(cid).unwrap().layers[0];
    l.stretch = stretch;
    (l.in_point, l.out_point, l.start_time) = (Tick::ZERO, Tick::from_seconds_f64(out), Tick::from_seconds_f64(out));
    (p, cid)
}

/// A time-reversed layer plays its audio backwards instead of being silent (#3239): at -100 %
/// sample for sample what Backwards plays on the forward layer, in any block size.
#[test]
fn a_reversed_layer_plays_its_audio_backwards() {
    let n = SR as usize;
    let (p, cid) = reversed(None, &[], false, -100.0, 1.0);
    let m = mix(&p, &Signal(ramp), cid, 0.0, n);
    // Comp sample k plays source sample n − 1 − k.
    for k in [0usize, 1, 2000, 4000, 7000] {
        let want = (n - 1 - k) as f32 / SR as f32;
        assert!((m[k * 2] - want).abs() < 1e-6 && (m[k * 2 + 1] + want).abs() < 1e-6, "k={k}: {} {}, want {want}", m[k * 2], m[k * 2 + 1]);
    }
    let (bp, bcid) = comp_with(Some("ec.audio.backwards"), &[], false);
    assert_eq!(m, mix(&bp, &Signal(ramp), bcid, 0.0, n), "not the mirror Backwards plays");
    let mut blocks = vec![];
    for k in 0..n / 320 {
        blocks.extend(mix(&p, &Signal(ramp), cid, (k * 320) as f64 / SR as f64, 320));
    }
    let worst = m.iter().zip(&blocks).map(|(a, b)| (a - b).abs()).fold(0.0f32, f32::max);
    assert!(worst < 1e-6, "block size changes the result by {worst}");
}

/// The speed of a reversed layer follows its stretch as a forward one's does: -50 % plays the
/// source twice as fast, -200 % at half speed, both backwards.
#[test]
fn a_reversed_layer_plays_at_its_stretch() {
    // -50 % over 0.5 s: comp sample k plays source sample 2 (n − 1 − k), n = 4000.
    let (p, cid) = reversed(None, &[], false, -50.0, 0.5);
    let m = mix(&p, &Signal(ramp), cid, 0.0, 4000);
    for k in [0usize, 1000, 3000] {
        let want = 2.0 * (3999 - k) as f32 / SR as f32;
        assert!((m[k * 2] - want).abs() < 1e-6, "-50 %, k={k}: {}, want {want}", m[k * 2]);
    }
    // -200 % over 2 s: comp sample k plays source sample (n − 1 − k) / 2, n = 16000, blended.
    let (p, cid) = reversed(None, &[], false, -200.0, 2.0);
    let m = mix(&p, &Signal(ramp), cid, 0.0, 16_000);
    for k in [0usize, 1, 5001, 12_000] {
        let want = (15_999 - k) as f32 / 2.0 / SR as f32;
        assert!((m[k * 2] - want).abs() < 1e-5, "-200 %, k={k}: {}, want {want}", m[k * 2]);
    }
}

/// Backwards on a reversed layer plays it forwards: the two reversals cancel.
#[test]
fn backwards_on_a_reversed_layer_plays_forwards() {
    let (p, cid) = reversed(Some("ec.audio.backwards"), &[], false, -100.0, 1.0);
    let (fp, fcid) = comp_with(None, &[], false);
    for (from, frames) in [(0.0, SR as usize), (0.25, 2000)] {
        let m = mix(&p, &Signal(ramp), cid, from, frames);
        assert!(m.iter().any(|v| v.abs() > 0.1), "silent from {from} s");
        assert_eq!(m, mix(&fp, &Signal(ramp), fcid, from, frames), "from {from} s");
    }
}

/// Effects on a reversed layer run on a clock that moves forwards with the samples at comp speed,
/// so a Tone joins up across blocks (preview's frame blocks and export's one-second blocks
/// agree), at -50 % too. On the layer-time clock, block k at -100 % would start 0.08 k s off:
/// 35.2 k cycles at 440 Hz, a phase jump.
#[test]
fn tone_on_a_reversed_layer_joins_up_across_blocks() {
    let mut vals: Vec<(&str, Value)> = vec![("frequency1", Value::Scalar(440.0))];
    for k in ["frequency2", "frequency3", "frequency4", "frequency5"] {
        vals.push((k, Value::Scalar(0.0)));
    }
    for stretch in [-100.0, -50.0] {
        let (p, cid) = reversed(Some("ec.audio.tone"), &vals, true, stretch, 1.0);
        let long = mix(&p, &Signal(ramp), cid, 0.2, 1600);
        assert!(rms(&long) > 0.05, "{stretch} %: silent: {}", rms(&long));
        let mut blocks = vec![];
        for k in 0..5 {
            blocks.extend(mix(&p, &Signal(ramp), cid, 0.2 + k as f64 * 0.04, 320));
        }
        let worst = long.iter().zip(&blocks).map(|(a, b)| (a - b).abs()).fold(0.0f32, f32::max);
        assert!(worst < 1e-3, "{stretch} %: block size changes the tone by {worst}");
    }
}

/// Footage audio on its sample grid, as the media pool decodes it: a read from any time starts
/// at the sample at or before it. Sample n is `f(n / rate)` over [0, 2) s.
struct Grid(fn(f64) -> (f32, f32));
impl FootageSource for Grid {
    fn frame(&self, _: ItemId, _: &Footage, _: Tick) -> Option<Arc<Image>> {
        None
    }
    fn audio(&self, _: ItemId, _: &Footage, start: Tick, frames: usize, rate: u32) -> Option<Vec<f32>> {
        let s0 = start.to_units_floor(i64::from(rate));
        Some(
            (0..frames as i64)
                .flat_map(|i| {
                    let t = (s0 + i) as f64 / rate as f64;
                    let (l, r) = if (0.0..2.0).contains(&t) { (self.0)(t) } else { (0.0, 0.0) };
                    [l, r]
                })
                .collect(),
        )
    }
}

/// A stretched layer, forwards or reversed, gives the same samples mixed in one block as in
/// blocks of any size (preview's video-frame blocks, export's seconds): each block resamples
/// from the exact source position, not from the source sample a block happens to start on.
#[test]
fn stretched_layers_join_up_across_blocks() {
    // (stretch, out point, start): the reversed layers start at their out point, the -50 % one
    // off the sample grid (a third of a sample late), so its source positions are fractional.
    let third = Tick(Tick::from_seconds_f64(1.0 / SR as f64).0 / 3);
    for (stretch, out, start) in [
        (200.0, 2.0, Tick::ZERO),
        (-70.0, 0.7, Tick::from_seconds_f64(0.7)),
        (-50.0, 0.5, Tick(Tick::from_seconds_f64(0.5).0 + third.0)),
        (-200.0, 2.0, Tick::from_seconds_f64(2.0)),
    ] {
        let (mut p, cid) = comp_with(None, &[], false);
        let l = &mut p.comp_mut(cid).unwrap().layers[0];
        l.stretch = stretch;
        (l.in_point, l.out_point, l.start_time) = (Tick::ZERO, Tick::from_seconds_f64(out), start);
        let n = 3210;
        let long = mix(&p, &Grid(ramp), cid, 0.1, n);
        assert!(long.iter().any(|v| v.abs() > 0.05), "{stretch} %: silent");
        for block in [321, 107] {
            let mut blocks = vec![];
            for k in 0..n / block {
                blocks.extend(mix(&p, &Grid(ramp), cid, 0.1 + (k * block) as f64 / SR as f64, block));
            }
            let worst = long.iter().zip(&blocks).map(|(a, b)| (a - b).abs()).fold(0.0f32, f32::max);
            assert!(worst < 1e-6, "{stretch} %, blocks of {block}: off by {worst}");
        }
    }
}

/// At 200 % the last sample of a block blends with the source sample after it, as inside the
/// block, instead of holding the one before.
#[test]
fn a_stretched_block_ends_on_a_blended_sample() {
    let (mut p, cid) = comp_with(None, &[], false);
    let l = &mut p.comp_mut(cid).unwrap().layers[0];
    l.stretch = 200.0;
    (l.in_point, l.out_point, l.start_time) = (Tick::ZERO, Tick::from_seconds_f64(2.0), Tick::ZERO);
    let m = mix(&p, &Grid(ramp), cid, 0.0, 320);
    // Comp sample 319 plays source position 159.5.
    let want = 159.5 / SR as f32;
    assert!((m[319 * 2] - want).abs() < 1e-6, "{}, want {want}", m[319 * 2]);
}

/// Records the longest audio read and answers with a short run, so an unbounded request fails
/// the assert below instead of allocating.
struct Longest(AtomicUsize);
impl FootageSource for Longest {
    fn frame(&self, _: ItemId, _: &Footage, _: Tick) -> Option<Arc<Image>> {
        None
    }
    fn audio(&self, _: ItemId, _: &Footage, _: Tick, frames: usize, _: u32) -> Option<Vec<f32>> {
        self.0.fetch_max(frames, Ordering::Relaxed);
        Some(vec![0.25; frames.min(4096) * 2])
    }
}

/// Tiny, huge, zero and non-finite stretches, and fast precomps nested in fast precomps, read
/// at most MAX_READ source frames at a time and mix to finite samples (a tiny positive stretch
/// asked for 10⁸ times the block, and its precomp buffer could abort the process).
#[test]
fn extreme_stretches_read_bounded_source() {
    let stretches = [1e-6, -1e-6, 0.5, -0.5, 1.0, -1.0, 1e12, -1e12, f64::MIN_POSITIVE, 0.0, f64::NAN, f64::INFINITY, f64::NEG_INFINITY];
    for stretch in stretches {
        let (mut p, cid) = comp_with(None, &[], false);
        p.comp_mut(cid).unwrap().layers[0].stretch = stretch;
        let src = Longest(AtomicUsize::new(0));
        let m = mix(&p, &src, cid, 0.0, 800);
        let longest = src.0.load(Ordering::Relaxed);
        assert!(longest <= MAX_READ, "stretch {stretch}: read {longest} frames at once");
        assert!(m.iter().all(|v| v.is_finite()), "stretch {stretch}");
    }
    // Exactly 1 %, give or take float noise, stays audible.
    let (mut p, cid) = comp_with(None, &[], false);
    p.comp_mut(cid).unwrap().layers[0].stretch = 1.0 - 1e-12;
    let m = mix(&p, &Longest(AtomicUsize::new(0)), cid, 0.0, 800);
    assert!(m.iter().any(|v| *v != 0.0), "1 % is silent");
    // A 1 % footage layer in a 1 % precomp: 10⁴ source samples per comp sample. The precomp layer
    // lasts 0.02 s, which plays the inner layer's 2 s once (backwards from its out point at -1 %).
    for sign in [1.0, -1.0] {
        let mut p = Project::default();
        let base = Comp::new(64, 64, FrameRate::new(25, 1), Tick::from_seconds_f64(2.0));
        let fid = p.add_item("x.wav", effectcraft_color::Label::SeaFoam, None, ItemKind::Footage(audio_footage()));
        let mut inner_l = build::layer(&mut p, &base, "a", LayerSource::Footage { item: fid }, (64, 64), None);
        inner_l.stretch = sign;
        (inner_l.in_point, inner_l.out_point, inner_l.start_time) =
            (Tick::ZERO, Tick::from_seconds_f64(2.0), if sign < 0.0 { Tick::from_seconds_f64(2.0) } else { Tick::ZERO });
        let mut inner = base.clone();
        inner.layers = vec![inner_l].into();
        let inner_id = p.add_item("Inner", effectcraft_color::Label::Sandstone, None, ItemKind::Comp(inner.into()));
        let mut pre = build::layer(&mut p, &base, "pre", LayerSource::Comp { item: inner_id }, (64, 64), None);
        pre.stretch = sign;
        let pre_out = Tick::from_seconds_f64(0.02);
        (pre.in_point, pre.out_point, pre.start_time) = (Tick::ZERO, pre_out, if sign < 0.0 { pre_out } else { Tick::ZERO });
        let mut outer = base.clone();
        outer.layers = vec![pre].into();
        let outer_id = p.add_item("Outer", effectcraft_color::Label::Sandstone, None, ItemKind::Comp(outer.into()));
        let src = Longest(AtomicUsize::new(0));
        let m = mix(&p, &src, outer_id, 0.0, 800);
        let longest = src.0.load(Ordering::Relaxed);
        assert!(longest > 0 && longest <= MAX_READ, "nested {sign}%: read {longest} frames at once");
        assert!(m.iter().all(|v| v.is_finite()));
    }
}

#[test]
fn high_low_pass_attenuates() {
    fn hi(t: f64) -> (f32, f32) {
        let v = (2.0 * std::f64::consts::PI * 3000.0 * t).sin() as f32;
        (v, v)
    }
    let vals = [("filterOptions", Value::Enum(1)), ("cutoffFrequency", Value::Scalar(200.0))];
    let (p, cid) = comp_with(Some("ec.audio.highlowpass"), &vals, false);
    let r = rms(&mix(&p, &Signal(hi), cid, 0.5, 800));
    assert!(r < 0.02, "{r}");
    let (p, cid) = comp_with(None, &[], false);
    let r = rms(&mix(&p, &Signal(hi), cid, 0.5, 800));
    assert!(r > 0.6, "{r}");
}

#[test]
fn delay_offsets_across_blocks() {
    fn click(t: f64) -> (f32, f32) {
        if (t * SR as f64).round() as i64 == 2000 { (1.0, 1.0) } else { (0.0, 0.0) }
    }
    let vals = [("delayTime", Value::Scalar(100.0)), ("feedback", Value::Scalar(0.0))];
    let (p, cid) = comp_with(Some("ec.audio.delay"), &vals, false);
    // The block starts after the click (0.25 s): the echo at 0.35 s still comes from pre-roll.
    let m = mix(&p, &Signal(click), cid, 0.3, 800);
    let i = 2800 - 2400;
    assert!((m[i * 2] - 0.375).abs() < 1e-5, "{}", m[i * 2]);
    assert_eq!(m.iter().filter(|v| v.abs() > 1e-6).count(), 2);
}

#[test]
fn stereo_mixer_pans() {
    fn left(_: f64) -> (f32, f32) {
        (0.5, 0.0)
    }
    let (p, cid) = comp_with(Some("ec.audio.stereomixer"), &[("leftPan", Value::Scalar(100.0))], false);
    let m = mix(&p, &Signal(left), cid, 0.2, 10);
    assert!(m.chunks(2).all(|f| f[0].abs() < 1e-6 && (f[1] - 0.5).abs() < 1e-6), "{:?}", &m[..4]);
}

/// Key `prop` of layer 0 (`effect`: in its first effect, else in Audio) from `a` at 0 s to `b` at 1 s.
fn key(p: &mut Project, cid: ItemId, effect: bool, prop: &str, a: Value, b: Value) {
    let l = &mut p.comp_mut(cid).unwrap().layers[0];
    let g = if effect { l.props.sub_mut("effects").unwrap().children[0].as_group_mut().unwrap() } else { l.props.sub_mut("audio").unwrap() };
    g.get_mut(prop).unwrap().keys = vec![Keyframe::new(Tick::ZERO, a), Keyframe::new(Tick::from_seconds_f64(1.0), b)];
}

/// Left samples of a mix of constant 0.5 audio over the layer's 1 s, in blocks of `block` samples.
fn left_ramp(p: &Project, cid: ItemId, block: usize) -> Vec<f32> {
    fn half(_: f64) -> (f32, f32) {
        (0.5, 0.5)
    }
    let mut m = vec![];
    for k in 0..SR as usize / block {
        m.extend(mix(p, &Signal(half), cid, (k * block) as f64 / SR as f64, block));
    }
    m.iter().step_by(2).copied().collect()
}

/// Keyframed Audio Levels and Stereo Mixer levels ramp smoothly inside a block (export mixes one
/// second at a time), instead of holding the value at the block's first sample.
#[test]
fn animated_levels_ramp_within_a_block() {
    let (mut levels, lc) = comp_with(None, &[], false);
    key(&mut levels, lc, false, "levels", Value::Vec2([-60.0, -60.0]), Value::Vec2([0.0, 0.0]));
    let (mut mixer, mc) = comp_with(Some("ec.audio.stereomixer"), &[], false);
    key(&mut mixer, mc, true, "leftLevel", Value::Scalar(0.0), Value::Scalar(100.0));
    for (name, p, cid, mid) in [("levels", &levels, lc, 0.5 * 10f32.powf(-1.5)), ("stereo mixer", &mixer, mc, 0.25)] {
        let one = left_ramp(p, cid, SR as usize);
        assert!(one.windows(2).all(|w| w[1] >= w[0]), "{name}: not monotonic");
        assert!(one[100] < one[4000] && one[4000] < one[7900], "{name}: {} {} {}", one[100], one[4000], one[7900]);
        assert!((one[4000] / mid - 1.0).abs() < 0.05, "{name}: {} at 0.5 s, want {mid}", one[4000]);
        assert_eq!(one, left_ramp(p, cid, 320), "{name}: block size changes the result");
    }
}

#[test]
fn tone_makes_a_solid_audible_at_its_frequency() {
    let mut vals: Vec<(&str, Value)> = vec![("frequency1", Value::Scalar(500.0))];
    for k in ["frequency2", "frequency3", "frequency4", "frequency5"] {
        vals.push((k, Value::Scalar(0.0)));
    }
    let (p, cid) = comp_with(Some("ec.audio.tone"), &vals, true);
    assert!(comp_has_audio(&p, cid));
    let m = mix(&p, &Signal(ramp), cid, 0.0, SR as usize);
    let left: Vec<f32> = m.iter().step_by(2).copied().collect();
    let ups = left.windows(2).filter(|w| w[0] <= 0.0 && w[1] > 0.0).count();
    assert!((ups as i64 - 500).abs() <= 1, "{ups}");
    // The out point (1 s) silences it.
    let after = mix(&p, &Signal(ramp), cid, 1.0, 100);
    assert!(after.iter().all(|v| *v == 0.0));
    let (p, cid) = comp_with(None, &[], true);
    assert!(!comp_has_audio(&p, cid));
}

/// Mixing in video-frame blocks gives the same samples as one long block (pre-roll makes
/// effects stateless across calls), so preview and export agree.
#[test]
fn blocks_match_one_long_mix() {
    fn noise(t: f64) -> (f32, f32) {
        let x = ((t * 12345.678).sin() * 43758.5453).fract() as f32;
        (x, -x)
    }
    for id in [
        "ec.audio.reverb",
        "ec.audio.basstreble",
        "ec.audio.flangechorus",
        "ec.audio.modulator",
        "ec.audio.delay",
        "ec.audio.parametriceq",
        "ec.audio.compressor",
        "ec.audio.gate",
        "ec.audio.distortion",
    ] {
        let vals: Vec<(&str, Value)> = match id {
            "ec.audio.basstreble" => vec![("bass", Value::Scalar(50.0))],
            "ec.audio.parametriceq" => vec![("band1BoostCut", Value::Scalar(9.0))],
            _ => vec![],
        };
        let (p, cid) = comp_with(Some(id), &vals, false);
        let long = mix(&p, &Signal(noise), cid, 0.2, 1600);
        let mut blocks = vec![];
        for k in 0..5 {
            blocks.extend(mix(&p, &Signal(noise), cid, 0.2 + k as f64 * 0.04, 320));
        }
        let worst = long.iter().zip(&blocks).map(|(a, b)| (a - b).abs()).fold(0.0f32, f32::max);
        assert!(worst < 2e-3, "{id}: {worst}");
    }
}

#[test]
fn peak_summary_bins() {
    let s: Vec<f32> = (0..10).flat_map(|i| [i as f32 * 0.1, -(i as f32) * 0.1]).collect();
    let p = peak_summary(&s, 4);
    assert_eq!(p.len(), 3);
    assert!(p[0][0].abs() < 1e-6 && (p[0][1] - 0.3).abs() < 1e-6);
    assert!((p[1][2] + 0.7).abs() < 1e-6 && (p[1][3] + 0.4).abs() < 1e-6);
    let f = audio_footage();
    let peaks = footage_peaks(&Signal(ramp), ItemId(1), &f, Tick::from_seconds_f64(2.0), 100);
    assert_eq!(peaks.len(), 200);
    assert!((peaks[150][1] - 1.51).abs() < 0.01, "{:?}", peaks[150]);
}

/// Audio Spectrum reads its Audio Layer's samples at the frame time, so the layer cache keys it
/// by time: a cached frame after the sound starts matches an uncached render (#209).
#[test]
fn audio_spectrum_follows_time_through_the_layer_cache() {
    fn late_tone(t: f64) -> (f32, f32) {
        let v = if t < 0.5 { 0.0 } else { (2.0 * std::f64::consts::PI * 1000.0 * t).sin() as f32 };
        (v, v)
    }
    let mut p = Project::default();
    let comp = Comp::new(64, 64, FrameRate::new(25, 1), Tick::from_seconds_f64(2.0));
    let audio = p.add_item("x.wav", effectcraft_color::Label::SeaFoam, None, ItemKind::Footage(audio_footage()));
    let a = build::layer(&mut p, &comp, "a", LayerSource::Footage { item: audio }, (64, 64), None);
    let sid = p.add_item("S", effectcraft_color::Label::Red, None, ItemKind::Solid(Solid { color: [0.0; 3], width: 64, height: 64, pixel_aspect: 1.0 }));
    let mut s = build::layer(&mut p, &comp, "s", LayerSource::Solid { item: sid }, (64, 64), None);
    let spec = effectcraft_effects::find("ec.generate.audiospectrum").unwrap();
    let mut next = p.next_id;
    let mut g = effectcraft_effects::instantiate(spec, &mut Ids(&mut next), spec.name, [64.0, 64.0]);
    p.next_id = next;
    g.prop_mut("audioLayer").unwrap().value = Value::Layer(Some(a.id.0));
    s.props.sub_mut("effects").unwrap().children.push(g.into());
    let mut comp = comp;
    comp.layers = vec![s, a].into();
    let cid = p.add_item("C", effectcraft_color::Label::Sandstone, None, ItemKind::Comp(comp.into()));

    let src = Signal(late_tone);
    let render = |t: f64, cache: Option<&crate::LayerCache>| {
        let mut r = crate::Renderer::new(&p, &src, crate::RenderOpts::default());
        r.cache = cache;
        r.comp_frame(cid, Tick::from_seconds_f64(t))
    };
    let lit = |img: &Image| img.data.iter().filter(|px| px[0] + px[1] + px[2] > 0.1).count();
    let cache = crate::LayerCache::default();
    let silent = render(0.0, Some(&cache));
    let cached = render(0.8, Some(&cache));
    let fresh = render(0.8, None);
    assert!(lit(&fresh) > lit(&silent), "the tone draws more than the baseline: {} vs {}", lit(&fresh), lit(&silent));
    assert_eq!(cached.data, fresh.data, "cached {} px, uncached {} px", lit(&cached), lit(&fresh));
}