fix decklink-out: use stream_frame_ counter for DeckLink scheduling instead of TAI-based grains_read_

nodes/decklink-out/src/decklink_out_node.cpp

@@ -190,6 +190,7 @@ bool DeckLinkOutNode::open_device() {
         frame->Release();
     }
 
+    stream_frame_ = preroll_frames_;
     if (output_->StartScheduledPlayback(0, time_scale_, 1.0) != S_OK) {
         spdlog::error("DeckLink-out: failed to start scheduled playback");
         return false;
@@ -267,9 +268,10 @@ void DeckLinkOutNode::schedule_frame(void* mxl_payload, long width, long height,
         buf->Release();
     }
 
-    auto stream_time = grains_read_ * frame_duration_;
+    auto stream_time = stream_frame_ * frame_duration_;
     output_->ScheduleVideoFrame(frame, stream_time, frame_duration_, time_scale_);
     frame->Release();
+    stream_frame_++;
 }
 
 void DeckLinkOutNode::process() {