When switching output cards, do it from the mixer thread.

[nageru] / mixer.h

diff --git a/mixer.h b/mixer.h
index b7c5ef790761fcab8fae0d9b4659d4ee63e53fc9..9e4c4d52a222e0d16a38693479f6e91859061269 100644 (file)
--- a/mixer.h
+++ b/mixer.h
@@ -234,6 +234,25 @@ public:
                return cards[card_index].capture->get_description();
        }
 
+       // The difference between this and the previous function is that if a card
+       // is used as the current output, get_card_description() will return the
+       // fake card that's replacing it for input, whereas this function will return
+       // the card's actual name.
+       std::string get_output_card_description(unsigned card_index) const {
+               assert(card_can_be_used_as_output(card_index));
+               assert(card_index < num_cards);
+               if (cards[card_index].parked_capture) {
+                       return cards[card_index].parked_capture->get_description();
+               } else {
+                       return cards[card_index].capture->get_description();
+               }
+       }
+
+       bool card_can_be_used_as_output(unsigned card_index) const {
+               assert(card_index < num_cards);
+               return cards[card_index].output != nullptr;
+       }
+
        std::map<uint32_t, bmusb::VideoMode> get_available_video_modes(unsigned card_index) const {
                assert(card_index < num_cards);
                return cards[card_index].capture->get_available_video_modes();
@@ -285,9 +304,17 @@ public:
                video_encoder->change_x264_bitrate(rate_kbit);
        }
 
+       int get_output_card_index() const {  // -1 = no output, just stream.
+               return desired_output_card_index;
+       }
+
+       void set_output_card(int card_index) { // -1 = no output, just stream.
+               desired_output_card_index = card_index;
+       }
+
 private:
        void configure_card(unsigned card_index, bmusb::CaptureInterface *capture, bool is_fake_capture, DeckLinkOutput *output);
-       void set_output_card(int card_index); // -1 = no output, just stream.
+       void set_output_card_internal(int card_index);  // Should only be called from the mixer thread.
        void bm_frame(unsigned card_index, uint16_t timecode,
                bmusb::FrameAllocator::Frame video_frame, size_t video_offset, bmusb::VideoFormat video_format,
                bmusb::FrameAllocator::Frame audio_frame, size_t audio_offset, bmusb::AudioFormat audio_format);
@@ -310,7 +337,15 @@ private:
        std::unique_ptr<Theme> theme;
        std::atomic<unsigned> audio_source_channel{0};
        std::atomic<int> master_clock_channel{0};  // Gets overridden by <output_card_index> if set.
-       std::atomic<int> output_card_index{-1};  // -1 for none.
+       int output_card_index = -1;  // -1 for none.
+
+       // The mechanics of changing the output card are so intricately connected
+       // with the work the mixer thread is doing. Thus, we don't change it directly,
+       // we just set this variable instead, which signals to the mixer thread that
+       // it should do the change before the next frame. This simplifies locking
+       // considerations immensely.
+       std::atomic<int> desired_output_card_index{-1};
+
        std::unique_ptr<movit::EffectChain> display_chain;
        std::unique_ptr<ChromaSubsampler> chroma_subsampler;
        std::unique_ptr<VideoEncoder> video_encoder;