1 files changed, 16 insertions, 8 deletions

diff --git a/src/wx/film_viewer.cc b/src/wx/film_viewer.cc
index b01498fc8..dcee453d4 100644
--- a/src/wx/film_viewer.cc
+++ b/src/wx/film_viewer.cc
@@ -88,6 +88,8 @@ rtaudio_callback(void* out, void *, unsigned int frames, double, RtAudioStreamSt
 
 FilmViewer::FilmViewer(wxWindow* p, bool wake)
 	: _closed_captions_dialog(new ClosedCaptionsDialog(p, this))
+	, _stream_time(0)
+	, _stream_time_update_needed(true)
 {
 #if wxCHECK_VERSION(3, 1, 0)
 	switch (Config::instance()->video_view_type()) {
@@ -353,7 +355,8 @@ FilmViewer::start_audio_stream_if_open()
 	auto& audio = AudioBackend::instance()->rtaudio();
 
 	if (audio.isStreamOpen()) {
-		audio.setStreamTime(_video_view->position().seconds());
+		_stream_time = _video_view->position().seconds();
+		_stream_time_update_needed = true;
 		auto error = AudioBackend::instance()->start_stream();
 		if (error) {
 			_audio_channels = 0;
@@ -696,7 +699,7 @@ FilmViewer::uncorrected_time() const
 	auto& audio = AudioBackend::instance()->rtaudio();
 
 	if (audio.isStreamRunning()) {
-		return DCPTime::from_seconds(audio.getStreamTime());
+		return DCPTime::from_seconds(_stream_time);
 	}
 
 	return _video_view->position();
@@ -712,8 +715,7 @@ FilmViewer::audio_time() const
 		return {};
 	}
 
-	return DCPTime::from_seconds(audio.getStreamTime()) -
-		DCPTime::from_frames(average_latency(), _film->audio_frame_rate());
+	return DCPTime::from_seconds(_stream_time) - DCPTime::from_frames(average_latency(), _film->audio_frame_rate());
 }
 
 
@@ -727,6 +729,15 @@ FilmViewer::time() const
 int
 FilmViewer::audio_callback(void* out_p, unsigned int frames)
 {
+	auto& audio = AudioBackend::instance()->rtaudio();
+
+	if (_stream_time_update_needed) {
+		audio.setStreamTime(_stream_time);
+		_stream_time_update_needed = false;
+	} else {
+		_stream_time = audio.getStreamTime();
+	}
+
 	while (true) {
 		auto t = _butler->get_audio(Butler::Behaviour::NON_BLOCKING, reinterpret_cast<float*>(out_p), frames);
 		if (!t || DCPTime(uncorrected_time() - *t) < one_video_frame()) {
@@ -736,10 +747,7 @@ FilmViewer::audio_callback(void* out_p, unsigned int frames)
 		/* The audio we just got was (very) late; drop it and get some more. */
 	}
 
-	auto& audio = AudioBackend::instance()->rtaudio();
-
-	boost::mutex::scoped_lock lm(_latency_history_mutex, boost::try_to_lock);
-	if (lm) {
+	if (auto lm = boost::mutex::scoped_lock(_latency_history_mutex, boost::try_to_lock)) {
 		_latency_history.push_back(audio.getStreamLatency());
 		if (_latency_history.size() > static_cast<size_t>(_latency_history_count)) {
 			_latency_history.pop_front();