Warn if doing a gain calculation might cause clipping.

2 files changed, 38 insertions, 10 deletions

diff --git a/src/wx/audio_panel.cc b/src/wx/audio_panel.cc
index 5523d2539..d6137ad9f 100644
--- a/src/wx/audio_panel.cc
+++ b/src/wx/audio_panel.cc
@@ -258,13 +258,22 @@ AudioPanel::gain_calculate_button_clicked ()
 		return;
 	}
 
-	_gain->wrapped()->SetValue(_gain->wrapped()->GetValue() + *c);
+	optional<float> old_peak_dB = peak ();
+	double old_value = _gain->wrapped()->GetValue();
+	_gain->wrapped()->SetValue(old_value + *c);
 
 	/* This appears to be necessary, as the change is not signalled,
 	   I think.
 	*/
 	_gain->view_changed ();
 
+	optional<float> peak_dB = peak ();
+	if (old_peak_dB && *old_peak_dB < -0.5 && peak_dB && *peak_dB > -0.5) {
+		error_dialog (this, _("It is not possible to adjust the content's gain for this fader change as it would cause the DCP's audio to clip.  The gain has not been changed."));
+		_gain->wrapped()->SetValue (old_value);
+		_gain->view_changed ();
+	}
+
 	d->Destroy ();
 }
 
@@ -360,22 +369,40 @@ AudioPanel::show_clicked ()
 	_audio_dialog->Show ();
 }
 
-void
-AudioPanel::setup_peak ()
+/** @return If there is one selected piece of audio content, return its peak value in dB (if known) */
+optional<float>
+AudioPanel::peak () const
 {
-	ContentList sel = _parent->selected_audio ();
 	optional<float> peak_dB;
 
-	if (sel.size() != 1) {
-		_peak->SetLabel (wxT (""));
-	} else {
+	ContentList sel = _parent->selected_audio ();
+	if (sel.size() == 1) {
 		shared_ptr<Playlist> playlist (new Playlist);
 		playlist->add (_parent->film(), sel.front());
 		try {
-			shared_ptr<AudioAnalysis> analysis (new AudioAnalysis (_parent->film()->audio_analysis_path (playlist)));
-			peak_dB = 20 * log10 (analysis->overall_sample_peak().first.peak) + analysis->gain_correction (playlist);
-			_peak->SetLabel (wxString::Format (_("Peak: %.2fdB"), *peak_dB));
+			shared_ptr<AudioAnalysis> analysis (new AudioAnalysis(_parent->film()->audio_analysis_path(playlist)));
+			peak_dB = 20 * log10 (analysis->overall_sample_peak().first.peak) + analysis->gain_correction(playlist);
 		} catch (...) {
+
+		}
+	}
+
+	return peak_dB;
+}
+
+void
+AudioPanel::setup_peak ()
+{
+	ContentList sel = _parent->selected_audio ();
+
+	optional<float> peak_dB = peak ();
+	if (sel.size() != 1) {
+		_peak->SetLabel (wxT(""));
+	} else {
+		peak_dB = peak ();
+		if (peak_dB) {
+			_peak->SetLabel (wxString::Format(_("Peak: %.2fdB"), *peak_dB));
+		} else {
 			_peak->SetLabel (_("Peak: unknown"));
 		}
 	}
diff --git a/src/wx/audio_panel.h b/src/wx/audio_panel.h
index 09aae0552..f7161f10a 100644
--- a/src/wx/audio_panel.h
+++ b/src/wx/audio_panel.h
@@ -50,6 +50,7 @@ private:
 	void setup_sensitivity ();
 	void reference_clicked ();
 	void add_to_grid ();
+	boost::optional<float> peak () const;
 
 	wxCheckBox* _reference;
 	wxStaticText* _reference_note;