DeckLinkSender green screen fix

shared/DeckLinkSender.hpp

@@ -44,7 +44,7 @@ public:
 
     ~DeckLinkSender() {
         if (decklink_output) {
-            decklink_output->StopScheduledPlayback(0, nullptr, 1);
+            if (playback_started_) decklink_output->StopScheduledPlayback(0, nullptr, 1);
             decklink_output->DisableVideoOutput();
             if (has_audio) decklink_output->DisableAudioOutput();
             decklink_output->SetScheduledFrameCompletionCallback(nullptr);
@@ -107,33 +107,18 @@ public:
         r = decklink_output->RowBytesForPixelFormat(bmdFormat10BitYUV, width, &row_bytes);
         if (r != S_OK) throw std::runtime_error("Could not get row bytes for pixel format");
 
-        // Pre-fill 3 black frames and schedule them to prime the pipeline.
+        // Create frame pool. Frames start in free_frames; submit_frame() schedules
-        // The card fires ScheduledFrameCompleted once each is done, at which point
+        // them as live content arrives. StartScheduledPlayback is deferred until
-        // submit_frame() can reclaim and reschedule them with live video.
+        // kPreroll frames have been scheduled so the card has a buffer to draw from.
         constexpr size_t kPreroll = 3;
         for (size_t i = 0; i < kPreroll; ++i) {
             IDeckLinkMutableVideoFrame* vf = nullptr;
             r = decklink_output->CreateVideoFrame(
                 width, height, row_bytes, bmdFormat10BitYUV, bmdFrameFlagDefault, &vf);
             if (r != S_OK) throw std::runtime_error("Could not create video frame");
-
-            IDeckLinkVideoBuffer* buf = nullptr;
-            vf->QueryInterface(IID_IDeckLinkVideoBuffer, (void**)&buf);
-            buf->StartAccess(bmdBufferAccessWrite);
-            void* ptr = nullptr;
-            buf->GetBytes(&ptr);
-            if (ptr) dmf::v210::fill_black(static_cast<uint8_t*>(ptr), width, height, row_bytes);
-            buf->EndAccess(bmdBufferAccessWrite);
-            buf->Release();
-
-            decklink_output->ScheduleVideoFrame(
-                vf, static_cast<BMDTimeValue>(i * fps_den), fps_den, fps_num);
             all_frames.push_back(vf);
+            free_frames.push_back(vf);
         }
-        scheduled_time = static_cast<int64_t>(kPreroll) * fps_den;
-
-        r = decklink_output->StartScheduledPlayback(0, fps_num, 1.0);
-        if (r != S_OK) throw std::runtime_error("Could not start scheduled playback");
     }
 
     // Blocks until a frame slot is free (returned by the card via callback),
@@ -169,6 +154,11 @@ public:
         const int64_t t = scheduled_time;
         scheduled_time += video_info.fps_den;
         decklink_output->ScheduleVideoFrame(vf, t, video_info.fps_den, video_info.fps_num);
+
+        if (!playback_started_ && ++frames_scheduled_ >= kPreroll) {
+            playback_started_ = true;
+            decklink_output->StartScheduledPlayback(0, video_info.fps_num, 1.0);
+        }
     }
 
     // Converts float32 planar → interleaved int32 and pushes to DeckLink audio buffer.
@@ -232,6 +222,8 @@ private:
     std::vector<IDeckLinkMutableVideoFrame*> free_frames;
 
     // Scheduling state — only written from submit_frame/submit_audio (single-threaded caller)
+    bool                 playback_started_ = false;
+    size_t               frames_scheduled_ = 0;
     int64_t              scheduled_time    = 0; // next video frame position (fps_num units)
     int64_t              audio_stream_time = 0; // next audio batch position (sample units)
     std::vector<int32_t> audio_convert_buf;     // reused across submit_audio calls