Bug 1932 - (Residual) Fix stopping behavior with Play-At-Speed.

1. The rate actually used by the sound card now sets the stopping sample number.
2. The tolerance in the 'stop position' is additionally trimmed to 20 samples.

src/AudioIO.h

@@ -483,22 +483,23 @@ class AUDACITY_DLL_API AudioIO final {
    void SetCaptureMeter(AudacityProject *project, MeterPanel *meter);
    void SetPlaybackMeter(AudacityProject *project, MeterPanel *meter);
 
+   /** \brief Return a valid sample rate that is supported by the current I/O
+   * device(s).
+   *
+   * The return from this function is used to determine the sample rate that
+   * audacity actually runs the audio I/O stream at. if there is no suitable
+   * rate available from the hardware, it returns 0.
+   * The sampleRate argument gives the desired sample rate (the rate of the
+   * audio to be handeled, i.e. the currently Project Rate).
+   * capturing is true if the stream is capturing one or more audio channels,
+   * and playing is true if one or more channels are being played. */
+   double GetBestRate(bool capturing, bool playing, double sampleRate);
+
 private:
    /** \brief Set the current VU meters - this should be done once after
     * each call to StartStream currently */
    void SetMeters();
 
-   /** \brief Return a valid sample rate that is supported by the current I/O
-    * device(s).
-    *
-    * The return from this function is used to determine the sample rate that
-    * audacity actually runs the audio I/O stream at. if there is no suitable
-    * rate available from the hardware, it returns 0.
-    * The sampleRate argument gives the desired sample rate (the rate of the
-    * audio to be handeled, i.e. the currently Project Rate).
-    * capturing is true if the stream is capturing one or more audio channels,
-    * and playing is true if one or more channels are being played. */
-   double GetBestRate(bool capturing, bool playing, double sampleRate);
 
    /** \brief Opens the portaudio stream(s) used to do playback or recording
     * (or both) through.

src/Project.cpp

@@ -1306,6 +1306,20 @@ AudioIOStartStreamOptions AudacityProject::GetDefaultPlayOptions()
    return options;
 }
 
+AudioIOStartStreamOptions AudacityProject::GetSpeedPlayOptions()
+{
+   auto PlayAtSpeedRate = gAudioIO->GetBestRate(
+      false,     //not capturing
+      true,      //is playing
+      GetRate()  //suggested rate
+   );
+   AudioIOStartStreamOptions options{ PlayAtSpeedRate };
+   options.timeTrack = GetTracks()->GetTimeTrack();
+   options.listener = this;
+   return options;
+}
+
+
 void AudacityProject::UpdatePrefsVariables()
 {
    gPrefs->Read(wxT("/AudioFiles/ShowId3Dialog"), &mShowId3Dialog, true);

src/Project.h

@@ -188,6 +188,7 @@ class AUDACITY_DLL_API AudacityProject final : public wxFrame,
    virtual void ApplyUpdatedTheme();
 
    AudioIOStartStreamOptions GetDefaultPlayOptions();
+   AudioIOStartStreamOptions GetSpeedPlayOptions();
 
    TrackList *GetTracks() { return mTracks.get(); }
    const TrackList *GetTracks() const { return mTracks.get(); }

src/tracks/ui/Scrubbing.cpp

@@ -462,7 +462,7 @@ bool Scrubber::StartSpeedPlay(double speed, double time0, double time1)
    mMaxSpeed = speed;
    mDragging = false;
 
-   AudioIOStartStreamOptions options(mProject->GetDefaultPlayOptions());
+   AudioIOStartStreamOptions options(mProject->GetSpeedPlayOptions());
    options.pScrubbingOptions = &mOptions;
    options.timeTrack = NULL;
    mOptions.startClockTimeMillis = ::wxGetLocalTimeMillis();
@@ -499,11 +499,11 @@ bool Scrubber::StartSpeedPlay(double speed, double time0, double time1)
    });
    
    mScrubSpeedDisplayCountdown = 0;
-   // last buffer should not be any bigger than this.
-   double lastBuffer = (2 * ScrubPollInterval_ms) / 1000.0;
+   // Aim to stop within 20 samples of correct position.
+   double stopTolerance = 20.0 / options.rate;
    mScrubToken =
-      // Reduce time by 'lastBuffer' fudge factor, so that the Play will stop.
-      ctb->PlayPlayRegion(SelectedRegion(time0, time1-lastBuffer), options,
+      // Reduce time by 'stopTolerance' fudge factor, so that the Play will stop.
+      ctb->PlayPlayRegion(SelectedRegion(time0, time1-stopTolerance), options,
          PlayMode::normalPlay, appearance, backwards);
 
    if (mScrubToken >= 0) {