On Windows platforms MidiOutput::sendBlockOfMessages() always seems to have at least 0.5 second latency from the moment you send MIDI data. This latency gets larger and larger the longer your computer is on. I’ve had over 3 second latencies. This doesn’t happen on Mac.
Attached to this post is a minimal sized application which demonstrates the issue well. Choose the MIDI input and output and press any note on your MIDI keyboard. The application sends the incoming MIDI notes immediately to the selected MIDI output. You’ll notice that there is a large latency which renders the JUCE’s MidiOutput::sendBlockOfMessages() unusable on Windows.
AudioAppDemo.zip (27.0 KB)