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

[nageru] / mixer.cpp

diff --git a/mixer.cpp b/mixer.cpp
index 457734d29578d80696cb2dfdb55f22b669a5e625..a83d66ef7194a9ff21b01dbe4843c73bc1d852b9 100644 (file)
--- a/mixer.cpp
+++ b/mixer.cpp
@@ -203,7 +203,7 @@ Mixer::Mixer(const QSurfaceFormat &format, unsigned num_cards)
                alsa.reset(new ALSAOutput(OUTPUT_FREQUENCY, /*num_channels=*/2));
        }
        if (global_flags.output_card != -1) {
-               set_output_card(global_flags.output_card);
+               set_output_card_internal(global_flags.output_card);
        }
 }
 
@@ -260,11 +260,11 @@ void Mixer::configure_card(unsigned card_index, CaptureInterface *capture, bool
        audio_mixer.trigger_state_changed_callback();
 }
 
-void Mixer::set_output_card(int card_index)
+void Mixer::set_output_card_internal(int card_index)
 {
-       if (card_index == output_card_index) {
-               return;
-       }
+       // We don't really need to take card_mutex, since we're in the mixer
+       // thread and don't mess with any queues (which is the only thing that happens
+       // from other threads), but it's probably the safest in the long run.
        unique_lock<mutex> lock(card_mutex);
        if (output_card_index != -1) {
                // Switch the old card from output to input.
@@ -285,6 +285,9 @@ void Mixer::set_output_card(int card_index)
        if (card_index != -1) {
                CaptureCard *card = &cards[card_index];
                bmusb::CaptureInterface *capture = card->capture.get();
+               // TODO: DeckLinkCapture::stop_dequeue_thread can actually take
+               // several seconds to complete (blocking on DisableVideoInput);
+               // see if we can maybe do it asynchronously.
                lock.unlock();
                capture->stop_dequeue_thread();
                lock.lock();
@@ -590,6 +593,10 @@ void Mixer::thread_func()
        int stats_dropped_frames = 0;
 
        while (!should_quit) {
+               if (desired_output_card_index != output_card_index) {
+                       set_output_card_internal(desired_output_card_index);
+               }
+
                CaptureCard::NewFrame new_frames[MAX_VIDEO_CARDS];
                bool has_new_frame[MAX_VIDEO_CARDS] = { false };