exporttask: snap to timebase when exporting video

This is a bit of a hack to prevent #2119 from causing problems. The reality is this probably requires a deeper re-think of how the timeline should and shouldn't work - this issue is more of a symptom of something deeper than a simple bug in and of itself.

app/task/export/export.cpp

@@ -51,8 +51,6 @@ ExportTask::ExportTask(ViewerOutput *viewer_node,
 
 bool ExportTask::Run()
 {
-  TimeRange range;
-
   // For safety, if we're overwriting, we save to a temporary filename and then only overwrite it
   // at the end
   QString real_filename = params_.filename();
@@ -111,10 +109,10 @@ bool ExportTask::Run()
 
   if (params_.has_custom_range()) {
     // Render custom range only
-    range = params_.custom_range();
+    export_range_ = params_.custom_range();
   } else {
     // Render entire sequence
-    range = TimeRange(0, viewer()->GetLength());
+    export_range_ = TimeRange(0, viewer()->GetLength());
   }
 
   frame_time_ = 0;
@@ -152,15 +150,19 @@ bool ExportTask::Run()
   TimeRange subtitle_range;
 
   if (params_.video_enabled()) {
-    video_range = {range};
+    if (export_range_.in() > 0) {
+      export_range_.set_in(Timecode::snap_time_to_timebase(export_range_.in(), video_params().frame_rate_as_time_base()));
+    }
+
+    video_range = {export_range_};
   }
 
   if (params_.audio_enabled()) {
-    audio_range = {range};
+    audio_range = {export_range_};
   }
 
   if (subtitles_enabled) {
-    subtitle_range = range;
+    subtitle_range = export_range_;
   }
 
   Render(color_manager_, video_range, audio_range, subtitle_range, RenderMode::kOnline, nullptr,
@@ -201,11 +203,7 @@ bool ExportTask::Run()
 
 bool ExportTask::FrameDownloaded(FramePtr f, const rational &time)
 {
-  rational actual_time = time;
-
-  if (params_.has_custom_range()) {
-    actual_time -= params_.custom_range().in();
-  }
+  rational actual_time = time - export_range_.in();
 
   time_map_.insert(actual_time, f);
 
@@ -233,11 +231,7 @@ bool ExportTask::FrameDownloaded(FramePtr f, const rational &time)
 
 bool ExportTask::AudioDownloaded(const TimeRange &range, const SampleBuffer &samples)
 {
-  TimeRange adjusted_range = range;
-
-  if (params_.has_custom_range()) {
-    adjusted_range -= params_.custom_range().in();
-  }
+  TimeRange adjusted_range = range - export_range_.in();
 
   if (adjusted_range.in() == audio_time_) {
     if (!WriteAudioLoop(adjusted_range, samples)) {

app/task/export/export.h

@@ -73,6 +73,8 @@ private:
 
   rational audio_time_;
 
+  TimeRange export_range_;
+
 };
 
 }