Consolidate: run clip effects over the clip and a bounded tail

render_clips allocated and ran a clip-effects workspace spanning the
whole selection for every clip with effects, however short the clip.
Many tiny effect clips in a long selection multiplied allocation and
effect processing by the selection length.

Process each clip's effects in reused 4096-frame blocks from the clip's
start (the effects start from silence, so nothing comes out before it)
through its end, then keep rendering the tail until a block falls below
-180 dBFS or 10 s past the clip's end.

crates/mix/src/offline.rs

@@ -131,33 +131,60 @@ pub fn fold_down_stereo(fmt: ChannelFormat, ch: &[Vec<f32>]) -> Vec<Vec<f32>> {
     out
 }
 
+/// Block size for clip effects in [`render_clips`].
+const CLIP_FX_BLOCK: usize = 4096;
+/// Most a clip effect keeps rendering past its clip's end in [`render_clips`], in seconds.
+const MAX_CLIP_FX_TAIL_SECONDS: f64 = 10.0;
+/// A tail block whose peak is below this (-180 dBFS) ends a clip effect's tail.
+const CLIP_FX_TAIL_FLOOR: f32 = 1e-9;
+
 /// Render only one track's clips (no mixer processing) — Consolidate.
 pub fn render_clips(s: &Session, track: TrackId, range: Range) -> Vec<Vec<f32>> {
     let Some(t) = s.track(track) else { return Vec::new() };
     let len = usize::try_from(range.len().max(0)).unwrap_or(0).min(MAX_RENDER_SAMPLES / t.channels().max(1));
     let mut out = vec![vec![0.0f32; len]; t.channels().max(1)];
     let mut scratch = Vec::new();
+    // One reusable block for every clip with effects.
+    let mut block: Vec<Vec<f32>> = Vec::new();
+    let max_tail = s.sample_rate.samples(MAX_CLIP_FX_TAIL_SECONDS).max(0);
     for c in t.clips().iter().filter(|c| !c.muted && c.range().overlaps(&range)) {
         match clip_fx_params(s, c.id.0) {
             None => render_clip(s, c, range.start, len, &mut out, &mut scratch),
             Some(params) => {
-                let mut tmp = vec![vec![0.0f32; len]; out.len()];
-                render_clip(s, c, range.start, len, &mut tmp, &mut scratch);
-                let mut fx = ClipFx::new(s.sample_rate.as_f64() as f32, tmp.len());
+                if block.len() != out.len() {
+                    block = vec![vec![0.0f32; CLIP_FX_BLOCK]; out.len()];
+                }
+                let mut fx = ClipFx::new(s.sample_rate.as_f64() as f32, out.len());
                 fx.configure(params);
-                let mut done = 0;
+                // The effects start from silence, so nothing comes out before the clip starts:
+                // process from there through the clip and a bounded tail, not the whole selection.
+                let offset = |at: Samples| usize::try_from(at.saturating_sub(range.start).max(0)).unwrap_or(usize::MAX).min(len);
+                let first = offset(c.start);
+                let clip_end = offset(c.end());
+                let tail_end = offset(c.end().saturating_add(max_tail));
+                let mut done = first;
                 while done < len {
-                    let n = (len - done).min(4096);
-                    let mut block: Vec<Vec<f32>> = tmp.iter().map(|ch| ch.get(done..done + n).map(<[f32]>::to_vec).unwrap_or_default()).collect();
+                    let n = (len - done).min(CLIP_FX_BLOCK);
+                    for ch in &mut block {
+                        ch.fill(0.0);
+                    }
+                    if done < clip_end {
+                        render_clip(s, c, range.start.saturating_add(done as i64), n, &mut block, &mut scratch);
+                    }
                     fx.process(&mut block, n);
+                    let mut peak = 0.0f32;
                     for (o, b) in out.iter_mut().zip(block.iter()) {
                         if let Some(dst) = o.get_mut(done..done + n) {
                             for (x, y) in dst.iter_mut().zip(b.iter()) {
                                 *x += *y;
+                                peak = peak.max(y.abs());
                             }
                         }
                     }
                     done += n;
+                    if done >= clip_end && (done >= tail_end || peak < CLIP_FX_TAIL_FLOOR) {
+                        break;
+                    }
                 }
             }
         }

crates/mix/src/tests.rs

@@ -1208,3 +1208,74 @@ fn gain_ramp_matches_converting_both_ends_every_sample() {
         }
     }
 }
+
+/// Consolidate's clip-effect pass, processing every clip's effects across the whole selection
+/// (what `render_clips` did before it limited them to the clip and its tail).
+fn render_clips_full_span(s: &Session, track: TrackId, range: Range) -> Vec<Vec<f32>> {
+    let t = s.track(track).unwrap();
+    let len = range.len() as usize;
+    let mut out = vec![vec![0.0f32; len]; t.channels().max(1)];
+    let mut scratch = Vec::new();
+    for c in t.clips().iter().filter(|c| !c.muted && c.range().overlaps(&range)) {
+        let params = crate::clips::clip_fx_params(s, c.id.0).unwrap();
+        let mut tmp = vec![vec![0.0f32; len]; out.len()];
+        crate::clips::render_clip(s, c, range.start, len, &mut tmp, &mut scratch);
+        let mut fx = crate::clips::ClipFx::new(48_000.0, tmp.len());
+        fx.configure(params);
+        for done in (0..len).step_by(4096) {
+            let n = (len - done).min(4096);
+            let mut block: Vec<Vec<f32>> = tmp.iter().map(|ch| ch[done..done + n].to_vec()).collect();
+            fx.process(&mut block, n);
+            for (o, b) in out.iter_mut().zip(&block) {
+                o[done..done + n].iter_mut().zip(b).for_each(|(x, y)| *x += y);
+            }
+        }
+    }
+    out
+}
+
+#[test]
+fn consolidate_clip_effects_cover_the_clip_and_its_tail() {
+    let fx_sets: [&[(&str, f64)]; 2] = [&[("comp.lookahead", 5.0), ("comp.threshold", -20.0), ("gain", -6.0)], &[("eq.hpf_on", 1.0), ("gain", 3.0)]];
+    for (k, params) in fx_sets.iter().enumerate() {
+        let mut s = Session::default();
+        let t = s.add_track(TrackKind::Audio, ChannelFormat::Mono, None);
+        s.pool.insert(SourceId(900), Arc::new(SourceAudio::new(AudioBuffer { sample_rate: 48_000, channels: vec![vec![0.5; 4800]] })));
+        let cid = s.new_clip_id();
+        s.track_mut(t).unwrap().playlist_mut().unwrap().clips.push(Clip::audio(cid, "dc", SourceId(900), 0, 20_000, 4800));
+        for (param, value) in params.iter() {
+            s.edit.values.insert(format!("clip_fx.{}.{param}", cid.0), *value);
+        }
+        let range = Range::new(5_000, 100_000);
+        let got = render_clips(&s, t, range);
+        let want = render_clips_full_span(&s, t, range);
+        assert_eq!(got.len(), want.len());
+        assert!(want[0].iter().any(|x| x.abs() > 0.05), "the fixture should sound");
+        if k == 0 {
+            // The compressor's lookahead output after the clip's end is kept.
+            assert!(got[0][20_000 + 4800 - 5_000 + 10].abs() > 1e-3);
+        }
+        for (i, (a, b)) in got[0].iter().zip(&want[0]).enumerate() {
+            assert!((a - b).abs() < 1e-5, "set {k}, sample {i}: {a} vs {b}");
+        }
+    }
+}
+
+#[test]
+fn consolidate_many_tiny_effect_clips_stays_fast() {
+    // Thousands of one-sample clips with effects across a long selection: each one is processed
+    // over its own span, not the whole selection.
+    let mut s = Session::default();
+    let t = s.add_track(TrackKind::Audio, ChannelFormat::Mono, None);
+    s.pool.insert(SourceId(900), Arc::new(SourceAudio::new(AudioBuffer { sample_rate: 48_000, channels: vec![vec![0.5; 1]] })));
+    for i in 0..2000i64 {
+        let cid = s.new_clip_id();
+        s.track_mut(t).unwrap().playlist_mut().unwrap().clips.push(Clip::audio(cid, "x", SourceId(900), 0, i * 1000, 1));
+        s.edit.values.insert(format!("clip_fx.{}.gain", cid.0), -6.0);
+    }
+    let start = std::time::Instant::now();
+    let out = render_clips(&s, t, Range::new(0, 4_000_000));
+    assert!(start.elapsed() < std::time::Duration::from_secs(10), "{:?}", start.elapsed());
+    assert!((out[0][1000] - 0.5 * db_to_gain(-6.0)).abs() < 1e-6);
+    assert_eq!(out[0][1001], 0.0);
+}