From 170852d8db58dec0cc42b8624345569203de0a78 Mon Sep 17 00:00:00 2001
From: Vikram Bhaskaran <vikram.bhaskaran@outlook.com>
Date: Sun, 11 Oct 2026 02:00:58 +1100
Subject: [PATCH] #533: Preserve explicit export sample rates to avoid silent
 substitution.

---
 crates/engine/src/export_tests.rs   | 15 ++++++++++
 crates/export/src/settings.rs       | 11 +-------
 crates/export/src/settings_tests.rs | 44 +++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+), 10 deletions(-)

diff --git a/crates/engine/src/export_tests.rs b/crates/engine/src/export_tests.rs
index 2757ebba..cf514b49 100644
--- a/crates/engine/src/export_tests.rs
+++ b/crates/engine/src/export_tests.rs
@@ -64,6 +64,21 @@ fn export_integer_parameters_cannot_wrap_or_overflow() {
     assert!(s.execute("export.resolve", json!({"bitrateKbps":8000.0, "keyframeDistance":48.0})).is_ok(), "integer-valued floats are integers");
 }
 
+#[test]
+fn wav_resolve_honours_explicit_sample_rates() {
+    let mut s = demo();
+    for rate in [4000, 192_000, 192_001, 200_000, 352_800, 384_000] {
+        let result = s.execute("export.resolve", json!({"format":"wav", "settings":{"audio":{"sample_rate":rate}}})).unwrap();
+        assert_eq!(result["settings"]["audio"]["sample_rate"], rate);
+        assert_eq!(result["output"]["sampleRate"], rate);
+    }
+    let result = s.execute("export.resolve", json!({"format":"wav", "settings":{"audio":{"sample_rate":null}}})).unwrap();
+    assert_eq!(result["output"]["sampleRate"], 48_000);
+    for rate in [0, 384_001] {
+        assert!(s.execute("export.resolve", json!({"format":"wav", "settings":{"audio":{"sample_rate":rate}}})).is_err());
+    }
+}
+
 #[test]
 fn nested_camel_case_settings_are_honoured() {
     let mut s = demo();
diff --git a/crates/export/src/settings.rs b/crates/export/src/settings.rs
index 8e8fc7ef..a0a083cd 100644
--- a/crates/export/src/settings.rs
+++ b/crates/export/src/settings.rs
@@ -406,16 +406,7 @@ impl ExportSettings {
             6.. => 6,
             _ => 2,
         };
-        Resolved {
-            width: w,
-            height: h,
-            rate,
-            sample_rate: self.audio.sample_rate.filter(|r| (8000..=192_000).contains(r)).unwrap_or(seq_sr),
-            channels,
-            target_kbps: target,
-            max_kbps: max,
-            keyint,
-        }
+        Resolved { width: w, height: h, rate, sample_rate: self.audio.sample_rate.unwrap_or(seq_sr), channels, target_kbps: target, max_kbps: max, keyint }
     }
 
     /// The audio codec actually used.
diff --git a/crates/export/src/settings_tests.rs b/crates/export/src/settings_tests.rs
index b494226b..d2410ae6 100644
--- a/crates/export/src/settings_tests.rs
+++ b/crates/export/src/settings_tests.rs
@@ -167,6 +167,50 @@ fn wav_and_aiff_audio_only() {
     }
 }
 
+#[test]
+fn wav_export_honours_explicit_sample_rates() {
+    let (project, sequence, sources) = matte([0.0, 0.0, 0.0, 1.0], 64, 36, Some(-6.0));
+    let dir = Scratch::new("wav-sample-rates");
+    for rate in [1, 4000, 7350, 8000, 48_000, 192_000, 192_001, 200_000, 352_800, 384_000] {
+        let settings = ExportSettings {
+            format: Format::Wav,
+            path: dir.path(&format!("{rate}.wav")),
+            audio: AudioSettings { sample_rate: Some(rate), ..Default::default() },
+            range: Some(TimeRange::new(Tick::ZERO, Tick(TICKS_PER_SECOND / 4))),
+            ..Default::default()
+        };
+        settings.validate().unwrap();
+        let resolved = settings.resolve(64, 36, FrameRate::FPS_24, 48_000);
+        assert_eq!(resolved.sample_rate, rate, "requested {rate} Hz");
+        export(&project, sequence, &settings, &sources, &Progress::default()).unwrap();
+        let bytes = std::fs::read(&settings.path).unwrap();
+        assert_eq!(u32::from_le_bytes(bytes[24..28].try_into().unwrap()), rate);
+        assert_eq!(u32::from_le_bytes(bytes[40..44].try_into().unwrap()), rate / 4 * 4, "quarter-second stereo 16-bit PCM");
+        if let Some(probe) = ffprobe_json(&["-show_streams"], &settings.path) {
+            assert_eq!(probe["streams"][0]["sample_rate"], rate.to_string());
+        }
+    }
+    let settings = ExportSettings { format: Format::Wav, ..Default::default() };
+    assert_eq!(settings.resolve(64, 36, FrameRate::FPS_24, 44_100).sample_rate, 44_100);
+}
+
+#[test]
+fn aac_export_rejects_unsupported_explicit_sample_rates() {
+    let (project, sequence, sources) = matte([0.0, 0.0, 0.0, 1.0], 64, 36, Some(-6.0));
+    let dir = Scratch::new("aac-sample-rates");
+    for rate in [4000, 192_001, 200_000, 384_000] {
+        let settings = ExportSettings {
+            path: dir.path(&format!("{rate}.mp4")),
+            audio: AudioSettings { sample_rate: Some(rate), ..Default::default() },
+            range: Some(TimeRange::new(Tick::ZERO, Tick(TICKS_PER_SECOND / 4))),
+            ..Default::default()
+        };
+        let error = export(&project, sequence, &settings, &sources, &Progress::default()).unwrap_err();
+        assert!(error.to_string().contains("sample rate"), "{error}");
+        assert!(!Path::new(&settings.path).exists(), "an unsupported rate must not produce a substitute file");
+    }
+}
+
 #[test]
 fn invalid_export_allocations_are_rejected_before_rendering() {
     let (project, sequence, _) = matte([1.0, 0.0, 0.0, 1.0], 64, 36, None);