fixed #641

rendering/renderthread.cpp

@@ -148,7 +148,7 @@ void RenderThread::paint() {
   params.video = true;
   params.texture_failed = false;
   params.wait_for_mutexes = true;
-  params.playback_speed = 1;
+  params.playback_speed = playback_speed_;
   params.blend_mode_program = blend_mode_program;
   params.premultiply_program = premultiply_program;
   params.backend_buffer1 = back_buffer_1.buffer();
@@ -230,6 +230,7 @@ void RenderThread::paint() {
 
 void RenderThread::start_render(QOpenGLContext *share,
                                 Sequence* s,
+                                int playback_speed,
                                 const QString& save,
                                 GLvoid* pixels,
                                 int pixel_linesize,
@@ -238,6 +239,8 @@ void RenderThread::start_render(QOpenGLContext *share,
 
   seq = s;
 
+  playback_speed_ = playback_speed;
+
   // stall any dependent actions
   texture_failed = true;