Bug report for JUCE: MidiOutput::sendBlockOfMessages() unusable on Windows?

[Kraku]

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)

[reuk]

I’ve addressed this issue on the other thread:

Weird MIDI output latency on Windows?

Thanks for providing some example code, that makes it much easier for us to investigate the problem. I can reproduce the issue with the provided sample. The docs for sendBlockOfMessages say that the time is specified using the same time base as Time::getMillisecondCounter. If I switch your demo to use that function in getNextAudioBlock instead of the HiRes version, then the timing issue seems to disappear and notes are immediately forwarded to the output. I tried artificially creating very r…