TIME CLOCK CALCULATOR F UPDATE
TIME CLOCK CALCULATOR F CODE

I suggest using AudioConvertHostTimeToNanos(), defined in, to convert from a MIDITimeStamp to an integral number of nanoseconds, then convert to double and go from there. If you did the math with integral microseconds or nanoseconds, you would get more accurate values. When you do the math (with a double!) to get back to BPM, that gives you either 125 beats/minute or 119.0476 beats/minute. Since you're computing integral milliseconds, that will appear to be either 20 or 21 ms. At 120 beats/minute and 24 clocks/beat, each clock arrives in 20.833 ms. Let's use 120 beats/minute as an example. The most important: You are working with integral numbers of milliseconds, which is not enough precision to get accurate beats/minute. There are a few mistakes here, some more important than others.

TIME CLOCK CALCULATOR F CODE

So if anyone sees some mistake in my code or have suggestions to make the whole thing more stable/accurate, please let me know !! Also the quantize routine is not perfect. I'm sure it can be optimized to be more accurate. I forked PGMidi and added some features such as BPM calculation and Quantization.

TIME CLOCK CALCULATOR F UPDATE

Thanks for your help Kurt ! very helpful ! UPDATE 2 Is there something else to consider to get something even more accurate?

Setting host to 100 BPM give me 100.401606.With this routine I now get something much more accurate BUT it is still off by a fraction of BPM below 150 and can be off up to 10 BPM on very high BPM (eg. Return (uint64_t)((time * s_timebase_info.numer) / (kOneThousand * s_timebase_nom)) Īs you can see I am now relying on the MidiPacket timeStamp instead of mach_absolute_time() which may be off by an inconstant amount.Īlso instead of using milliseconds for my BPM calculation I am now using nanoseconds for better accuracy. so divide by one thousand to get nanoseconds mach_absolute_time() returns billionth of seconds, (void) mach_timebase_info(&s_timebase_info) Static mach_timebase_info_data_t s_timebase_info Uint64_t convertTimeInNanoseconds(uint64_t time)

If(previousClockTime > 0 & currentClockTime > 0)ĭouble intervalInNanoseconds = convertTimeInNanoseconds(currentClockTime-previousClockTime) īPM = (1000000 / intervalInNanoseconds / 24) * 60 ĭispatch_async(dispatch_get_main_queue(), %f',BPM) Int status = statusByte >= 0xf0 ? statusByte : statusByte & 0xF0 What i'm first calculating the time elapsed between each midi clock using mach_absolute_time().įollowing Kurt answer, here is a much more accurate routine that works on iOS (as I'm not using CoreAudio/HostTime.h which is only available on OSX) double currentClockTime Int status = statusByte >= 0xf0 ? statusByte : statusByte > 4 104.16666666Ĭan someone please help me with this? I believe i'm probably not using a good strategy to calculate the BPM. MIDIPacket *packet = MIDIPacketListInit((MIDIPacketList*)packetList) (void) midiSource:(PGMidiSource*)input midiReceived:(const MIDIPacketList *)packetList Here is my current implementation to calculate the BPM double BPM From the doc this is happening from a high priority background thread. In PGMidi lib there is a method called while MIDI messages are received. I'm using CoreMIDI and PGMidi from Pete Goodliffe. I'm having some trouble calculating an accurate BPM from a receiving MIDI Clock (using Ableton Live in my tests for sending the MIDI clock).

Time clock calculator f