| Namespace | Microsoft.Windows.Devices.Midi2 |
|---|---|
| Type Name | MidiClock |
| Type | WinRT Runtime Class |
| IDL | MidiClock.idl |
| Library | Microsoft.Windows.Devices.Midi2.dll |
The MidiClock is what is used for all timestamps in Windows MIDI Services. Although it is internally backed by QueryPerformanceCounter, we recommend using the MidiClock type directly instead of calling QPC yourself.
Also note that QueryPerformanceCounter technically returns a signed 64 bit integer, but the timestamp values used in Windows MIDI Services are unsigned 64 bit integers. Typically, this is of no practical concern as the tick resolution is currently 100ns and takes tens of thousands of years to wrap around even with a 64 bit signed integer.
Note: The MIDI Clock is unrelated to wall clock time. It is an ever-increasing value of period
1/TimestampFrequencyseconds that starts over when the PC is rebooted. To convert to wall clock time, you need to get theMidiClock.Nowvalue at a known time, and then use that as a baseline until the next time you reboot the PC.
You can learn more about high-resolution timestamps in Windows at https://aka.ms/miditimestamp.
| Static Property | Description |
|---|---|
Now |
Returns the current timestamp |
TimestampFrequency |
Returns the number of timestamp ticks per second. This is calculated the first time it is called, and then cached for future calls. |
TimestampConstantSendImmediately |
Returns the constant to use when you want to send messages immediately and bypass outgoing message scheduling. Developers may use this value or simply provide 0 in place of the timestamp when sending messages. |
The static functions are for convenience in calculating offsets to a timestamp, and for converting between units.
| Static Function | Description |
|---|---|
ConvertTimestampTicksToNanoseconds(timestampValue) |
Converts the provided timestamp to nanoseconds |
ConvertTimestampTicksToMicroseconds(timestampValue) |
Converts the provided timestamp to microseconds |
ConvertTimestampTicksToMilliseconds(timestampValue) |
Converts the provided timestamp to milliseconds |
ConvertTimestampTicksToSeconds(timestampValue) |
Converts the provided timestamp to seconds |
When scheduling messages, you may want to use a more convenient time units. These functions make that easy.
| Static Function | Description |
|---|---|
OffsetTimestampByTicks(timestampValue, offsetTicks) |
Offsets a given timestamp by the provided (signed) number of ticks |
OffsetTimestampByMicroseconds(timestampValue, offsetMicroseconds) |
Offsets a given timestamp by the provided (signed) number of microseconds |
OffsetTimestampByMilliseconds(timestampValue, offsetMilliseconds) |
Offsets a given timestamp by the provided (signed) number of milliseconds |
OffsetTimestampBySeconds(timestampValue, offsetSeconds) |
Offsets a given timestamp by the provided (signed) number of seconds |
Windows supports putting the system timer into a low-latency / high-frequency mode. Drivers have more control over this, but applications can also specify that they want to enter a low-latency period, providing better timing characteristics. If you call the BeginLowLatencyTimerPeriod function, your application must call the EndLowLatencyTimePeriod before it closes. If drivers have not already set the timer period to the lowest value, these functions typically change the timer period from around 15ms to around 1ms.
| Static Function | Description |
|---|---|
GetCurrentSystemTimerInfo |
Returns a MidiSystemTimerSettings struct containing the current timer characteristics |
BeginLowLatencySystemTimerPeriod |
Signal that this application is putting the system into a low-latency timer period. Internally calls timeBeginPeriod |
EndLowLatencySystemTimerPeriod |
End the started low-latency timer period. You must call this before the application closes if you previously called the Begin function. Internally calls timeEndPeriod |
Windows MIDI Services is an open source project with all source available on GitHub. We have a great community on Discord as well. Between GitHub and Discord, you should find the information you are looking for.
