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fix(rendering): stale frames in same-clip cross-fades and seeks with the FFmpeg decoder #2661

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Merged
richiemcilroy merged 3 commits into from
Oct 17, 2026
Merged

fix(rendering): stale frames in same-clip cross-fades and seeks with the FFmpeg decoder #2661

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27546ac
fix(rendering): read the outgoing side of a same-clip transition from…
richiemcilroy Oct 17, 2026
7cea5ef
fix(rendering): seek the FFmpeg decoder when a request is behind its …
richiemcilroy Oct 17, 2026
559ed90
test(verify): drop the fixed long-crossfade xfail, keep seed 23's Lin…
richiemcilroy Oct 17, 2026
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23 changes: 17 additions & 6 deletions crates/editor/src/editor_instance.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1118,12 +1118,23 @@ impl EditorInstance {
_ = preview_rx.changed() => {
continue;
}
frames = outgoing_media.decoders.get_frames_initial(
outgoing.source_time as f32,
project.requires_camera(),
true,
outgoing_offsets,
) => frames,
frames = async {
let decoders = if outgoing.segment.recording_clip
== segment.recording_clip
{
outgoing_media.decoders.transition_side().await
} else {
&outgoing_media.decoders
};
decoders
.get_frames_initial(
outgoing.source_time as f32,
project.requires_camera(),
true,
outgoing_offsets,
)
.await
} => frames,
};
if let Some(outgoing_frames) = outgoing_frames {
let outgoing_zoom = outgoing_zoom_timelines
Expand Down
11 changes: 7 additions & 4 deletions crates/editor/src/playback.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -478,9 +478,13 @@ async fn decode_prefetched_frame(request: PrefetchDecodeRequest) -> PrefetchDeco
};
let transition = async {
let transition = transition?;
let transition_decoders = if transition.segment_index == segment_index {
transition.decoders.transition_side().await
} else {
&transition.decoders
};
let segment_frames = if is_initial {
transition
.decoders
transition_decoders
.get_frames_initial(
transition.segment_time as f32,
!hide_camera,
Expand All @@ -489,8 +493,7 @@ async fn decode_prefetched_frame(request: PrefetchDecodeRequest) -> PrefetchDeco
)
.await
} else {
transition
.decoders
transition_decoders
.get_frames(
transition.segment_time as f32,
!hide_camera,
Expand Down
8 changes: 6 additions & 2 deletions crates/export/src/preview.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -303,8 +303,12 @@ async fn render_preview_frame(
.find(|clip| clip.index == outgoing.segment.recording_clip)
.map(|clip| clip.offsets)
.unwrap_or_default();
let outgoing_frames = outgoing_media
.decoders
let outgoing_decoders = if outgoing.segment.recording_clip == segment.recording_clip {
outgoing_media.decoders.transition_side().await
} else {
outgoing_media.decoders
};
let outgoing_frames = outgoing_decoders
.get_frames(
outgoing.source_time as f32,
project_config.requires_camera() && !settings.cursor_only,
Expand Down
78 changes: 60 additions & 18 deletions crates/rendering/src/decoder/ffmpeg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -593,6 +593,9 @@ impl FfmpegDecoder {
// Previous vended frame number since the last reset, for pts-hole
// discovery (the reader vends in pts order between resets).
let mut prev_vended: Option<u32> = None;
// Newest frame the reader has vended since its last reset: where the
// reader is. The last sent frame is not, as it can be a cache hit.
let mut reader_at: Option<u32> = None;

let last_sent_frame = Rc::new(RefCell::new(None::<OutputFrame>));
let first_ever_frame = Rc::new(RefCell::new(None::<OutputFrame>));
Expand Down Expand Up @@ -636,6 +639,9 @@ impl FfmpegDecoder {
let mut sw_gap_hold: Option<OutputFrame> = None;
// Previous vended frame number since the last reset.
let mut sw_prev_vended: Option<u32> = None;
// Newest frame the reader has vended since its last reset: where the
// reader is. The last sent frame is not, as it can be a cache hit.
let mut sw_reader_at: Option<u32> = None;
let sw_last_sent_frame = Rc::new(RefCell::new(None::<OutputFrame>));
let sw_first_ever_frame = Rc::new(RefCell::new(None::<OutputFrame>));
let mut sw_frames = sw_this.frames();
Expand Down Expand Up @@ -669,6 +675,7 @@ impl FfmpegDecoder {
// The pre-decoded frame is a real vend: without seeding
// this, an opening static hold would never be recorded.
sw_prev_vended = Some(current_frame);
sw_reader_at = Some(current_frame);
}

let sw_decoder_type = DecoderType::FFmpegSoftware;
Expand Down Expand Up @@ -748,6 +755,16 @@ impl FfmpegDecoder {
continue;
}

// Nothing precedes the stream's first frame, so it holds
// for any earlier request; a later one needs a seek.
if let Some(first_frame) = sw_first_ever_frame.borrow().clone()
&& requested_frame <= first_frame.number
{
*sw_last_sent_frame.borrow_mut() = Some(first_frame.clone());
let _ = reply.send(first_frame.frame);
continue;
}

if is_backward_seek {
let best_cached_frame = sw_cache
.range(..=requested_frame)
Expand All @@ -766,14 +783,6 @@ impl FfmpegDecoder {
continue;
}

if requested_frame <= MAX_FRAME_LOOKBACK_TOLERANCE
&& let Some(first_frame) = sw_first_ever_frame.borrow().clone()
{
*sw_last_sent_frame.borrow_mut() = Some(first_frame.clone());
let _ = reply.send(first_frame.frame);
continue;
}

if let Err(error) = sw_this.reset(requested_time)
&& let Some(control) = &managed
{
Expand All @@ -787,6 +796,7 @@ impl FfmpegDecoder {
*sw_last_sent_frame.borrow_mut() = None;
sw_cache.clear();
sw_prev_vended = None;
sw_reader_at = None;
}

// Requests inside a KNOWN pts hole are answered with the
Expand Down Expand Up @@ -836,6 +846,11 @@ impl FfmpegDecoder {
let cache_min = requested_frame.saturating_sub(FRAME_CACHE_SIZE as u32 / 2);
let cache_max = requested_frame + FRAME_CACHE_SIZE as u32 / 2;

// The reader has already passed this uncached frame: it fell
// outside the cache window, or the last sent frame was a cache
// hit away from the reader. Reading on cannot reach it.
let behind_reader = sw_reader_at.is_some_and(|at| requested_frame <= at);

let is_far_forward = sw_last_sent_frame.borrow().as_ref().map_or_else(
|| {
if sw_first_ever_frame.borrow().is_some() {
Expand All @@ -855,7 +870,7 @@ impl FfmpegDecoder {
},
);

if is_far_forward {
if is_far_forward || behind_reader {
if let Err(error) = sw_this.reset(requested_time)
&& let Some(control) = &managed
{
Expand All @@ -869,6 +884,7 @@ impl FfmpegDecoder {
*sw_last_sent_frame.borrow_mut() = None;
sw_cache.clear();
sw_prev_vended = None;
sw_reader_at = None;
}

let mut exit = false;
Expand All @@ -895,6 +911,13 @@ impl FfmpegDecoder {
// the vend continuity that hole discovery
// relies on.
sw_prev_vended = None;
// The reader has still moved past it.
if let Ok(frame) = &frame
&& let Some(pts) = frame.pts()
{
sw_reader_at =
Some(pts_to_frame(pts - sw_start_time, sw_time_base, fps));
}
break;
}

Expand All @@ -917,6 +940,7 @@ impl FfmpegDecoder {
record_pts_hole(&mut sw_pts_holes, prev, current_frame);
}
sw_prev_vended = Some(current_frame);
sw_reader_at = Some(current_frame);

let mut cache_frame = CachedFrame::Raw {
frame,
Expand Down Expand Up @@ -1146,6 +1170,7 @@ impl FfmpegDecoder {
// The pre-decoded frame is a real vend: without seeding this,
// an opening static hold would never be recorded.
prev_vended = Some(current_frame);
reader_at = Some(current_frame);
info!(
"FFmpeg decoder '{}': pre-decoded first frame {} ({}x{})",
name, current_frame, video_width, video_height
Expand Down Expand Up @@ -1210,6 +1235,7 @@ impl FfmpegDecoder {
record_pts_hole(&mut pts_holes, prev, current_frame);
}
prev_vended = Some(current_frame);
reader_at = Some(current_frame);
let mut cache_frame = CachedFrame::Raw {
frame,
number: current_frame,
Expand Down Expand Up @@ -1312,6 +1338,16 @@ impl FfmpegDecoder {
continue;
}

// Nothing precedes the stream's first frame, so it holds
// for any earlier request; a later one needs a seek.
if let Some(first_frame) = first_ever_frame.borrow().clone()
&& requested_frame <= first_frame.number
{
*last_sent_frame.borrow_mut() = Some(first_frame.clone());
let _ = reply.send(first_frame.frame);
continue;
}

if is_backward_seek {
let best_cached_frame = cache
.range(..=requested_frame)
Expand All @@ -1330,14 +1366,6 @@ impl FfmpegDecoder {
continue;
}

if requested_frame <= MAX_FRAME_LOOKBACK_TOLERANCE
&& let Some(first_frame) = first_ever_frame.borrow().clone()
{
*last_sent_frame.borrow_mut() = Some(first_frame.clone());
let _ = reply.send(first_frame.frame);
continue;
}

if let Err(error) = this.reset(requested_time)
&& let Some(control) = &managed
{
Expand All @@ -1352,6 +1380,7 @@ impl FfmpegDecoder {
*last_sent_frame.borrow_mut() = None;
cache.clear();
prev_vended = None;
reader_at = None;
}

// Requests inside a KNOWN pts hole are answered with the
Expand Down Expand Up @@ -1406,6 +1435,11 @@ impl FfmpegDecoder {
let cache_min = requested_frame.saturating_sub(FRAME_CACHE_SIZE as u32 / 2);
let cache_max = requested_frame + FRAME_CACHE_SIZE as u32 / 2;

// The reader has already passed this uncached frame: it fell
// outside the cache window, or the last sent frame was a cache
// hit away from the reader. Reading on cannot reach it.
let behind_reader = reader_at.is_some_and(|at| requested_frame <= at);

let is_far_forward = last_sent_frame.borrow().as_ref().map_or_else(
|| {
if first_ever_frame.borrow().is_some() {
Expand All @@ -1423,7 +1457,7 @@ impl FfmpegDecoder {
|last| requested_frame.saturating_sub(last.number) > FRAME_CACHE_SIZE as u32,
);

if is_far_forward {
if is_far_forward || behind_reader {
if let Err(error) = this.reset(requested_time)
&& let Some(control) = &managed
{
Expand All @@ -1438,6 +1472,7 @@ impl FfmpegDecoder {
*last_sent_frame.borrow_mut() = None;
cache.clear();
prev_vended = None;
reader_at = None;
}

let mut exit = false;
Expand All @@ -1463,6 +1498,12 @@ impl FfmpegDecoder {
// The frame just pulled is discarded: it breaks the
// vend continuity that hole discovery relies on.
prev_vended = None;
// The reader has still moved past it.
if let Ok(frame) = &frame
&& let Some(pts) = frame.pts()
{
reader_at = Some(pts_to_frame(pts - start_time, time_base, fps));
}
break;
}

Expand All @@ -1485,6 +1526,7 @@ impl FfmpegDecoder {
record_pts_hole(&mut pts_holes, prev, current_frame);
}
prev_vended = Some(current_frame);
reader_at = Some(current_frame);

let mut cache_frame = CachedFrame::Raw {
frame,
Expand Down
1 change: 1 addition & 0 deletions crates/rendering/src/decoder/mod.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -2806,6 +2806,7 @@ mod managed_worker_tests {
screen: display.with_max_fallback_distance(crate::SCREEN_MAX_FALLBACK_DISTANCE),
camera: Some(camera.with_max_fallback_distance(crate::CAMERA_MAX_FALLBACK_DISTANCE)),
segment_offset: 10.25,
transition_readers: None,
};
let input = ManagedSegmentVideoInput::new(
0,
Expand Down
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