fix(recording): prevent double-count of VideoStartGate trim in mic_start_time

crates/recording/src/output_pipeline/core.rs

@@ -187,7 +187,15 @@ pub(crate) async fn apply_video_start_gate(
                     offset_ns = offset_ns as i64,
                     "Trimmed leading audio samples for encoder-pair alignment"
                 );
-                VideoStartGateAction::UseFrame(AudioFrame::new(trimmed, frame.timestamp))
+                // Advance the timestamp to the first *committed* sample so that
+                // first_timestamp (and therefore mic_start_time in metadata) reflects
+                // the actual capture time after the trim, not the pre-trim buffer start.
+                // Without this, the editor's mic_offset = display_start - mic_start equals
+                // trim_duration and causes it to skip that same duration a second time.
+                let trim_duration = Duration::from_nanos(
+                    trim_samples as u64 * 1_000_000_000 / sample_rate as u64,
+                );
+                VideoStartGateAction::UseFrame(AudioFrame::new(trimmed, frame.timestamp + trim_duration))
             }
             None => {
                 warn!(
@@ -4492,6 +4500,21 @@ mod tests {
                     let expected_trim =
                         ns_to_sample_count(video_start_ns, info.sample_rate) as usize;
                     assert_eq!(new_frame.inner.samples(), 2048 - expected_trim);
+                    // Timestamp must be advanced by the trim so that mic_start_time in
+                    // metadata reflects the first committed sample, preventing the editor
+                    // from double-counting the same gap as a skip offset.
+                    let trim_duration = Duration::from_nanos(
+                        expected_trim as u64 * 1_000_000_000 / info.sample_rate as u64,
+                    );
+                    let expected_ts = Timestamp::Instant(start + trim_duration);
+                    assert_eq!(
+                        new_frame
+                            .timestamp
+                            .signed_duration_since_secs(master_clock.timestamps()),
+                        expected_ts
+                            .signed_duration_since_secs(master_clock.timestamps()),
+                        "gate UseFrame timestamp must be advanced past the trimmed samples"
+                    );
                 }
                 other => panic!("expected UseFrame when audio leads, got {other:?}"),
             }