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Smooth out waveform/video playback cursor (lag, stutter, seek delay) #11627

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Merged
niksedk merged 6 commits into from
Jun 15, 2026
+434 −61
Merged

Smooth out waveform/video playback cursor (lag, stutter, seek delay) #11627

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04eb326
Smooth out waveform/video playback cursor
shanytc Jun 14, 2026
7437911
Make waveform seek instant and fix play-start cursor rush
shanytc Jun 14, 2026
f7465c8
Run the cursor timer above the video's render priority
shanytc Jun 14, 2026
b329fea
Smooth waveform scrolling in center mode
shanytc Jun 14, 2026
9a6922a
Maintain playhead estimate without a waveform; fix stale comment
shanytc Jun 15, 2026
e1e5474
Hold the playhead while mpv's clock is frozen after a seek
shanytc Jun 15, 2026
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274 changes: 222 additions & 52 deletions src/ui/Controls/AudioVisualizerControl/AudioVisualizer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1958,13 +1958,38 @@ private void DrawWaveForm(DrawingContext context, ref RenderContext renderCtx)
waveformHeight = renderCtx.WaveformHeight;
}

if (WaveformDrawStyle == WaveformDrawStyle.Classic)
// Rebuild the cached geometry only when the view actually changed; otherwise (e.g. the
// cursor moved) just replay the existing draw ops. See _waveformCacheDraws.
var key = BuildWaveformCacheKey(waveformHeight, ref renderCtx);
if (!_waveformCacheValid || !ReferenceEquals(_waveformCachePeaks, WavePeaks) || !key.Equals(_waveformCacheKey))
{
DrawWaveFormClassic(context, waveformHeight, ref renderCtx);
_waveformCacheDraws.Clear();
if (WaveformDrawStyle == WaveformDrawStyle.Classic)
{
BuildWaveFormClassic(waveformHeight, ref renderCtx);
}
else
{
BuildWaveFormFancy(waveformHeight, ref renderCtx);
}

_waveformCacheKey = key;
_waveformCachePeaks = WavePeaks;
_waveformCacheValid = true;
}
else

// The fancy style draws a center line; it depends only on width/height (already in the
// key) so it's cheap to draw live each render rather than caching it.
if (WaveformDrawStyle != WaveformDrawStyle.Classic)
{
var halfWaveformHeight = waveformHeight / 2;
context.DrawLine(_centerLinePen, new Point(0, halfWaveformHeight), new Point(renderCtx.Width, halfWaveformHeight));
}

for (var i = 0; i < _waveformCacheDraws.Count; i++)
{
DrawWaveFormFancy(context, waveformHeight, ref renderCtx);
var draw = _waveformCacheDraws[i];
context.DrawGeometry(null, draw.Pen, draw.Geometry);
}
}

Expand Down Expand Up @@ -2025,7 +2050,7 @@ private sealed class FancyBatch
private readonly Dictionary<int, FancyBatch> _fancyBatches = new(64);
private readonly List<int> _fancyBatchKeysInUse = new(64);

private void DrawWaveFormFancy(DrawingContext context, double waveformHeight, ref RenderContext renderCtx)
private void BuildWaveFormFancy(double waveformHeight, ref RenderContext renderCtx)
{
_isSelectedHelper.Reset(AllSelectedParagraphs, renderCtx.SampleRate);
var isSelectedHelper = _isSelectedHelper;
Expand All @@ -2043,9 +2068,6 @@ private void DrawWaveFormFancy(DrawingContext context, double waveformHeight, re
var peaksCount = peaks.Length;
var highestPeak = renderCtx.HighestPeak;

// Draw center line first
context.DrawLine(_centerLinePen, new Point(0, halfWaveformHeight), new Point(renderCtx.Width, halfWaveformHeight));

// Calculate the threshold for color transitions (as a fraction of the highest peak)
var lowThreshold = highestPeak * 0.3;
var mediumThreshold = highestPeak * 0.6;
Expand Down Expand Up @@ -2169,35 +2191,18 @@ private void DrawWaveFormFancy(DrawingContext context, double waveformHeight, re
}
}

// One DrawGeometry per pen, instead of two DrawLines per column.
// One cached geometry per pen, instead of two DrawLines per column.
// The gradient brush bounds become the entire waveform area instead of each
// individual line, so the gradient fades across the waveform vertically rather
// than per column.
for (var i = 0; i < keysInUse.Count; i++)
{
var batch = batches[keysInUse[i]];
var lines = batch.Lines;
if (lines.Count == 0)
{
continue;
}

var geom = new StreamGeometry();
using (var gctx = geom.Open())
{
for (var j = 0; j < lines.Count; j++)
{
var l = lines[j];
gctx.BeginFigure(new Point(l.X, l.YMax), false);
gctx.LineTo(new Point(l.X, l.YMin));
gctx.EndFigure(false);
}
}
context.DrawGeometry(null, batch.Pen, geom);
AddLineBatchToCache(batch.Pen, batch.Lines);
}
}

private void DrawWaveFormClassic(DrawingContext context, double waveformHeight, ref RenderContext renderCtx)
private void BuildWaveFormClassic(double waveformHeight, ref RenderContext renderCtx)
{
_isSelectedHelper.Reset(AllSelectedParagraphs, renderCtx.SampleRate);
var isSelectedHelper = _isSelectedHelper;
Expand All @@ -2209,7 +2214,7 @@ private void DrawWaveFormClassic(DrawingContext context, double waveformHeight,
return;
}

// See DrawWaveFormFancy: skip IList<T> interface dispatch in the per-pixel loop.
// See BuildWaveFormFancy: skip IList<T> interface dispatch in the per-pixel loop.
var peaks = WavePeaks.AsSpan();
var peaksCount = peaks.Length;

Expand Down Expand Up @@ -2262,14 +2267,138 @@ private void DrawWaveFormClassic(DrawingContext context, double waveformHeight,
}
}

DrawVerticalLineBatch(context, _paintWaveform, unselectedLines);
DrawVerticalLineBatch(context, _paintPenSelected, selectedLines);
AddLineBatchToCache(_paintWaveform, unselectedLines);
AddLineBatchToCache(_paintPenSelected, selectedLines);
}

// Pooled buffers for the classic waveform's two pens.
private readonly List<FancyLine> _classicUnselectedLines = new(2048);
private readonly List<FancyLine> _classicSelectedLines = new(2048);

// Cached waveform draw ops. Building the waveform is a per-pixel CPU loop that allocates
// geometry every render; doing it on every cursor tick (CurrentVideoPositionSeconds has
// AffectsRender) made playback stutter, worst over loud audio (extra glow geometry). We
// build the geometry once per view-state and just replay the draw calls while only the
// cursor moves. The key captures everything that changes the waveform pixels, so any real
// change (scroll, zoom, resize, selection, peaks, colors, style) rebuilds automatically.
private readonly List<(IPen Pen, Geometry Geometry)> _waveformCacheDraws = new(64);
private WaveformCacheKey _waveformCacheKey;
private bool _waveformCacheValid;
private object? _waveformCachePeaks;

private readonly struct WaveformCacheKey : IEquatable<WaveformCacheKey>
{
public readonly int Width;
public readonly double Height;
public readonly double WaveformHeight;
public readonly double StartPositionSeconds;
public readonly double ZoomFactor;
public readonly double VerticalZoomFactor;
public readonly double HighestPeak;
public readonly int SampleRate;
public readonly int DisplayMode;
public readonly int DrawStyle;
public readonly uint ColorMain;
public readonly uint ColorSelected;
public readonly uint ColorHigh;
public readonly int SelectionCount;
public readonly long SelectionHash;

public WaveformCacheKey(int width, double height, double waveformHeight, double startPositionSeconds,
double zoomFactor, double verticalZoomFactor, double highestPeak, int sampleRate, int displayMode,
int drawStyle, uint colorMain, uint colorSelected, uint colorHigh, int selectionCount, long selectionHash)
{
Width = width;
Height = height;
WaveformHeight = waveformHeight;
StartPositionSeconds = startPositionSeconds;
ZoomFactor = zoomFactor;
VerticalZoomFactor = verticalZoomFactor;
HighestPeak = highestPeak;
SampleRate = sampleRate;
DisplayMode = displayMode;
DrawStyle = drawStyle;
ColorMain = colorMain;
ColorSelected = colorSelected;
ColorHigh = colorHigh;
SelectionCount = selectionCount;
SelectionHash = selectionHash;
}

public bool Equals(WaveformCacheKey other) =>
Width == other.Width &&
Height.Equals(other.Height) &&
WaveformHeight.Equals(other.WaveformHeight) &&
StartPositionSeconds.Equals(other.StartPositionSeconds) &&
ZoomFactor.Equals(other.ZoomFactor) &&
VerticalZoomFactor.Equals(other.VerticalZoomFactor) &&
HighestPeak.Equals(other.HighestPeak) &&
SampleRate == other.SampleRate &&
DisplayMode == other.DisplayMode &&
DrawStyle == other.DrawStyle &&
ColorMain == other.ColorMain &&
ColorSelected == other.ColorSelected &&
ColorHigh == other.ColorHigh &&
SelectionCount == other.SelectionCount &&
SelectionHash == other.SelectionHash;

public override bool Equals(object? obj) => obj is WaveformCacheKey other && Equals(other);
public override int GetHashCode() => 0; // unused; cache does an exact Equals comparison
}

private static uint ToKeyColor(Color c) => ((uint)c.A << 24) | ((uint)c.R << 16) | ((uint)c.G << 8) | c.B;

private WaveformCacheKey BuildWaveformCacheKey(double waveformHeight, ref RenderContext renderCtx)
{
long selectionHash = 17;
var selection = AllSelectedParagraphs;
for (var i = 0; i < selection.Count; i++)
{
var p = selection[i];
selectionHash = selectionHash * 31 + p.StartTime.Ticks;
selectionHash = selectionHash * 31 + p.EndTime.Ticks;
}

return new WaveformCacheKey(
(int)Math.Ceiling(renderCtx.Width),
renderCtx.Height,
waveformHeight,
renderCtx.StartPositionSeconds,
renderCtx.ZoomFactor,
renderCtx.VerticalZoomFactor,
renderCtx.HighestPeak,
renderCtx.SampleRate,
(int)_displayMode,
(int)WaveformDrawStyle,
ToKeyColor(WaveformColor),
ToKeyColor(WaveformSelectedColor),
ToKeyColor(WaveformFancyHighColor),
selection.Count,
selectionHash);
}

private void AddLineBatchToCache(IPen pen, List<FancyLine> lines)
{
if (lines.Count == 0)
{
return;
}

var geom = new StreamGeometry();
using (var gctx = geom.Open())
{
for (var i = 0; i < lines.Count; i++)
{
var l = lines[i];
gctx.BeginFigure(new Point(l.X, l.YMax), false);
gctx.LineTo(new Point(l.X, l.YMin));
gctx.EndFigure(false);
}
}

_waveformCacheDraws.Add((pen, geom));
}

private static void DrawVerticalLineBatch(DrawingContext context, IPen pen, List<FancyLine> lines)
{
if (lines.Count == 0)
Expand Down Expand Up @@ -2306,6 +2435,56 @@ private void DrawParagraphs(DrawingContext context, ref RenderContext renderCtx)
}
}

// Subtitle text is otherwise re-shaped on every frame. At 60 fps the FormattedText shaping
// plus RemoveHtmlTags (regex) and SplitToLines for each visible paragraph churns enough
// short-lived garbage to trigger GC pauses, which show up as the cursor briefly freezing and
// then jumping. Cache the prepared text and the shaped FormattedText; both are cleared in
// ResetCache() when the waveform font/colors change.
private readonly Dictionary<string, FormattedText> _paragraphFormattedTextCache = new(512);
private readonly Dictionary<string, (List<string> Lines, string Unwrapped)> _paragraphTextCache = new(512);

private FormattedText GetCachedParagraphText(string text)
{
if (!_paragraphFormattedTextCache.TryGetValue(text, out var formatted))
{
if (_paragraphFormattedTextCache.Count > 8000)
{
_paragraphFormattedTextCache.Clear();
}

formatted = new FormattedText(text, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
_paragraphFormattedTextCache[text] = formatted;
}

return formatted;
}

private (List<string> Lines, string Unwrapped) GetPreparedParagraphText(string rawText)
{
if (!_paragraphTextCache.TryGetValue(rawText, out var prepared))
{
var text = HtmlUtil.RemoveHtmlTags(rawText, true);
if (text.Length > 200)
{
text = text.Substring(0, 100).TrimEnd() + "...";
}

var lines = text.SplitToLines();
var unwrapped = string.Join(" ", lines);
prepared = (lines, unwrapped);

if (_paragraphTextCache.Count > 8000)
{
_paragraphTextCache.Clear();
}

_paragraphTextCache[rawText] = prepared;
}

return prepared;
}

private void DrawParagraph(SubtitleLineViewModel paragraph, DrawingContext context, ref RenderContext renderCtx)
{
var currentRegionLeft = SecondsToXPositionOptimized(paragraph.StartTime.TotalSeconds - renderCtx.StartPositionSeconds, renderCtx.SampleRate, renderCtx.ZoomFactor);
Expand All @@ -2327,32 +2506,24 @@ private void DrawParagraph(SubtitleLineViewModel paragraph, DrawingContext conte
context.DrawLine(_paintLeft, new Point(currentRegionLeft, 0), new Point(currentRegionLeft, height));
context.DrawLine(_paintRight, new Point(currentRegionRight - 1, 0), new Point(currentRegionRight - 1, height));

// Draw clipped text
var text = HtmlUtil.RemoveHtmlTags(paragraph.Text, true);
if (text.Length > 200)
{
text = text.Substring(0, 100).TrimEnd() + "...";
}
// Draw clipped text (prepared text + shaped FormattedText are cached; see GetCachedParagraphText)
var prepared = GetPreparedParagraphText(paragraph.Text);

var textBounds = new Rect(currentRegionLeft + 1, 0, currentRegionWidth - 3, height);

using (context.PushClip(textBounds))
{
var arr = text.SplitToLines();
if (Se.Settings.Waveform.WaveformUnwrapText)
{
text = string.Join(" ", arr);
var formattedText = new FormattedText(text, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var formattedText = GetCachedParagraphText(prepared.Unwrapped);
context.DrawText(formattedText, new Point(currentRegionLeft + 3, 14));
}
else
{
double addY = 0;
foreach (var line in arr)
foreach (var line in prepared.Lines)
{
var formattedText = new FormattedText(line, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var formattedText = GetCachedParagraphText(line);
context.DrawText(formattedText, new Point(currentRegionLeft + 3, 14 + addY));
addY += formattedText.Height;
}
Expand Down Expand Up @@ -2405,8 +2576,7 @@ private void DrawParagraphFooter(DrawingContext context, SubtitleLineViewModel p
// the frame form ("00:00:02:12") without an explicit branch here.
var durationText = new TimeCode(paragraph.Duration.TotalMilliseconds).ToShortDisplayString();
var withDuration = $"#{paragraph.Number} {durationText}";
var probe = new FormattedText(withDuration, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var probe = GetCachedParagraphText(withDuration);

baseLine = probe.Width >= availableWidth
? $"#{paragraph.Number}"
Expand All @@ -2431,22 +2601,19 @@ private void DrawParagraphFooter(DrawingContext context, SubtitleLineViewModel p

if (baseLine != null)
{
var baseText = new FormattedText(baseLine, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var baseText = GetCachedParagraphText(baseLine);
var baseY = bottomY - baseText.Height;
context.DrawText(baseText, new Point(x, baseY));

if (cpsLine != null)
{
var cpsText = new FormattedText(cpsLine, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var cpsText = GetCachedParagraphText(cpsLine);
context.DrawText(cpsText, new Point(x, baseY - cpsText.Height));
}
}
else if (cpsLine != null)
{
var cpsText = new FormattedText(cpsLine, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
_typeface, _fontSize, _paintText);
var cpsText = GetCachedParagraphText(cpsLine);
context.DrawText(cpsText, new Point(x, bottomY - cpsText.Height));
}
}
Expand Down Expand Up @@ -3173,6 +3340,9 @@ internal void ResetCache()
_fancyWaveformGlowPenCache.Clear();
_fancyWaveformGradientCache.Clear();
_timeLineTextCache.Clear();
_paragraphFormattedTextCache.Clear();
_paragraphTextCache.Clear();
_waveformCacheValid = false;

_paintText = new SolidColorBrush(Se.Settings.Waveform.WaveformTextColor.FromHexToColor());
_typeface = new Typeface(UiUtil.GetDefaultFontName(), FontStyle.Normal, Se.Settings.Waveform.WaveformTextFontBold ? FontWeight.Bold : FontWeight.Normal);
Expand Down
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