Audio Device latencies & safety offsets on Mac

MacOSX and iOS
11

Good thought myhrman, but after a couple of hours of mucking around I’ve yet to see a non-zero stream latency.

The following code grafted into juce_mac_CoreAudio.cpp only checks the first stream, but I’ve tried looping through them all and checking that the AudioObjectGetPropertyData is successful. However I still only get zero unfortunately.

int getLatencyFromDevice (AudioObjectPropertyScope scope) const
{
    UInt32 deviceLatency = 0;
    UInt32 size = sizeof (deviceLatency);
    AudioObjectPropertyAddress pa;
    pa.mElement = kAudioObjectPropertyElementMaster;
    pa.mSelector = kAudioDevicePropertyLatency;
    pa.mScope = scope;
    AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &deviceLatency);

    UInt32 safetyOffset = 0;
    size = sizeof (safetyOffset);
    pa.mSelector = kAudioDevicePropertySafetyOffset;
    AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, &safetyOffset);

    // Query stream latency
    UInt32 streamLatency = 0;
    UInt32 numStreams;
    pa.mSelector = kAudioDevicePropertyStreams;
    if (OK(AudioObjectGetPropertyDataSize (deviceID, &pa, 0, nullptr, &numStreams)))
    {
        HeapBlock<AudioStreamID> streams (numStreams);
        size = sizeof (AudioStreamID*);
        if (OK(AudioObjectGetPropertyData (deviceID, &pa, 0, nullptr, &size, streams)))
        {
            pa.mSelector = kAudioStreamPropertyLatency;
            size = sizeof (streamLatency);
            // We could check all streams for the device, but it only ever seems to return the stream latency on the first stream
            AudioObjectGetPropertyData (streams[0], &pa, 0, nullptr, &size, &streamLatency);
        }
    }
    
    std::cout << "deviceLatency: " << String(deviceLatency).toRawUTF8() << ", ";
    std::cout << "safetyOffset: " << String(safetyOffset).toRawUTF8() << ", ";
    std::cout << "streamLatency: " << String(streamLatency).toRawUTF8() << std::endl;

    return (int) (deviceLatency + safetyOffset + streamLatency);
}