Fixes for the "bounce" at start of scrub

src/AudioIO.cpp

@@ -524,11 +524,10 @@ constexpr size_t TimeQueueGrainSize = 2000;
 
 struct AudioIO::ScrubState
 {
-   ScrubState(double t0, wxLongLong startClockMillis,
+   ScrubState(double t0,
               double rate,
               const ScrubbingOptions &options)
       : mRate(rate)
-      , mLastScrubTimeMillis(startClockMillis)
       , mStartTime( t0 )
    {
       const double t1 = options.bySpeed ? 1.0 : t0;
@@ -778,7 +777,17 @@ private:
    };
 
    struct Duration {
-      Duration (ScrubState &queue_) : queue(queue_) {}
+      Duration (ScrubState &queue_) : queue(queue_)
+      {
+         do {
+            clockTime = ::wxGetLocalTimeMillis();
+            duration = static_cast<long long>(
+               queue.mRate *
+                  (clockTime - queue.mLastScrubTimeMillis).ToDouble()
+                     / 1000.0
+            );
+         } while( duration <= 0 && (::wxMilliSleep(1), true) );
+      }
       ~Duration ()
       {
          if(!cancelled)
@@ -788,10 +797,8 @@ private:
       void Cancel() { cancelled = true; }
 
       ScrubState &queue;
-      const wxLongLong clockTime { ::wxGetLocalTimeMillis() };
-      const sampleCount duration { static_cast<long long>
-         (queue.mRate * (clockTime - queue.mLastScrubTimeMillis).ToDouble() / 1000.0)
-      };
+      wxLongLong clockTime;
+      sampleCount duration;
       bool cancelled { false };
    };
 
@@ -800,7 +807,7 @@ private:
    std::atomic<bool> mStopped { false };
    Data mData;
    const double mRate;
-   wxLongLong mLastScrubTimeMillis;
+   wxLongLong mLastScrubTimeMillis{ ::wxGetLocalTimeMillis() };
    struct Message {
       double end;
       ScrubbingOptions options;
@@ -1958,7 +1965,6 @@ int AudioIO::StartStream(const TransportTracks &tracks,
       mScrubState =
          std::make_unique<ScrubState>(
             mPlaybackSchedule.mT0,
-            scrubOptions.startClockTimeMillis,
             mRate,
             scrubOptions);
       mScrubDuration = 0;
@@ -1981,7 +1987,7 @@ int AudioIO::StartStream(const TransportTracks &tracks,
       // execute too much else
       if (mScrubState) {
          mOwningProject->GetScrubber().ContinueScrubbingPoll();
-         wxMilliSleep( Scrubber::ScrubPollInterval_ms );
+         wxMilliSleep( Scrubber::ScrubPollInterval_ms * 0.9 );
       }
       else
 #endif

src/tracks/ui/Scrubbing.cpp

@@ -51,7 +51,9 @@ enum {
    ScrubSpeedStepsPerOctave = 4,
 #endif
 
-   kOneSecondCountdown = 1000 / Scrubber::ScrubPollInterval_ms,
+   ScrubPollInterval_ms = 50,
+
+   kOneSecondCountdown = 1000 / ScrubPollInterval_ms,
 };
 
 static const double MinStutter = 0.2;
@@ -297,7 +299,6 @@ void Scrubber::MarkScrubStart(
 
    mScrubStartPosition = xx;
    ctb->UpdateStatusBar(mProject);
-   mOptions.startClockTimeMillis = ::wxGetLocalTimeMillis();
    mCancelled = false;
 }
 
@@ -424,7 +425,7 @@ bool Scrubber::MaybeStartScrubbing(wxCoord xx)
       }
       else
          // Wait to test again
-         mOptions.startClockTimeMillis = ::wxGetLocalTimeMillis();
+         ;
 
       if (IsScrubbing()) {
          mLastScrubPosition = xx;
@@ -462,7 +463,6 @@ bool Scrubber::StartSpeedPlay(double speed, double time0, double time1)
    AudioIOStartStreamOptions options(mProject->GetSpeedPlayOptions());
    options.pScrubbingOptions = &mOptions;
    options.timeTrack = NULL;
-   mOptions.startClockTimeMillis = ::wxGetLocalTimeMillis();
    mOptions.delay = (ScrubPollInterval_ms * 0.9 / 1000.0);
    mOptions.minSpeed = speed -0.01;
    mOptions.maxSpeed = speed +0.01;
@@ -634,7 +634,7 @@ void Scrubber::StartPolling()
    mpThread->Run();
 #endif
    
-   mPoller->Start(ScrubPollInterval_ms);
+   mPoller->Start(ScrubPollInterval_ms * 0.9);
 }
 
 void Scrubber::StopPolling()

src/tracks/ui/Scrubbing.h

@@ -58,10 +58,6 @@ struct ScrubbingOptions {
    // this is the minimum amount of playback allowed at the maximum speed:
    double minStutterTime {};
 
-   // Scrubbing needs the time of start of the mouse movement that began
-   // the scrub:
-   wxLongLong startClockTimeMillis { -1 };
-
    static double MaxAllowedScrubSpeed()
    { return 32.0; } // Is five octaves enough for your amusement?
    static double MinAllowedScrubSpeed()