The Set Tempo Meta event itself contains a delta field as well. Is this delta defined in the previous tempo or in the new tempo (the tempo in this event)?
Thanks
Delta times are expressed in MIDI ticks, which are independent of tempo.
If you are calculating the real-time duration in microseconds of the delta time of the new tempo, you would use the MPQN of the previous tempo event to perform that calculation.
Related
I have learned from my previous question “Get the same arrival rate across models” that for two models with the same arrival rate input, I can get the exact same arrivals generated in both models by setting the source block in both to “Interarrival time” and in the code, use exponential(lambda, 0, rand) where rand is a user-defined random number generator (RNG), for example, Random rand = new Random(1234). If prior to setting the source block to “Interarrival time” I had it set to “Rate Schedule” in which the schedule is of type rate that is provided from the database and in my case the rate (lambda) is not constant, it depends on the time of the day, how can I overcome this when setting the source block to “Interarrival time”?
Since it is not possible to set a seed for the arrival rate, you'll need to use interarrival times instead in your source.
However, since you also need to vary the interarrival time based on the time of day, you should write a function that returns different exponential random variables depending on the time of day and use that as your interarrival times.
Here is how I did that in AnyLogic:
And I made a quick plot of how many injections were occurring per hour just to verify that the rates are actually changing.
Perhaps I'm understanding the question wrong, but interarrival times can these not be transformed to arrival rate, so for example if interarrival time = 2minutes, the arrival rate is 0.5 per minute. If this is the case for your model, you can use in the source block arrivals defined by: a rate schedule (as shown in the figure below.)
After that in the schedule you can change the different arrival rates, so for example between 00:00 and 01:00 the arrival rate should be 1 as shown in the figure below:
I want to simulate a call center where the customers' arrival rate is different depending on the time slot. For example:
from 8am to 8:30am the rate is 50
from 8:30am to 9am the rate is 60
May I ask how I can set this in Anylogic?
First you create a schedule with the rate that you want:
this example has a default value rate of 10/hour and has the values you suggested for 8:00-9am.
And in the source you define your agent arrivals based on the schedule you created:
Recently I've been playing with the haskell ALSA interface, and I had to notice, that I do not really understand the concepts of tempo and PPQ.
Earlier I've written a Swig-Python interface to ALSA and in there I find the following piece of code (probably copied from somewhere else):
1 void AlsaMidiIfc::setTempo (int bpm) {
2 int queue = this->getOutQueue();
3 snd_seq_queue_tempo_t *tempo;
4 snd_seq_queue_tempo_alloca (&tempo);
5 snd_seq_queue_tempo_set_tempo(tempo, 60 * 1000000 / bpm);
6 snd_seq_queue_tempo_set_ppq(tempo, PPQ);
7 snd_seq_set_queue_tempo (mySeq, queue, tempo);
8 }
When I put an event into a queue, the time is always specified in ticks, right? So the only timing question to answer is "how long is a tick?".
What is the point of specifying two values, i.e. tempo and PPQ?
What would be the effect of changing the tempo, but leaving PPQ as it
is?
If I don't set PPQ at all, but only the tempo, what would be the
result?
Standard MIDI Files use these two values (tempo and PPQ) to specify the tempo.
The ALSA sequencer just uses the same mechanism.
The tempo value is the number of microseconds per quarter note.
Increasing it will increase the length of a tick, i.e., make playback slower.
A PPQ value of zero would be invalid.
i need help..
i need to know exactly midi delta time format?is it millisecond,tick or what??
and i need formula to convert timestamp in millisecond into midi delta time...
thanks before..
Delta time is always specified in ticks, which are determined by the PPQ (pulses per quarter note).
So given an offset in milliseconds, you must first convert that to samples (using the sample rate), and then to pulses based on the current tempo and the PPQ.
I want to know how to convert MIDI ticks to actual playback seconds.
For example, if the MIDI PPQ (Pulses per quarter note) is 1120, how would I convert it into real world playback seconds?
The formula is 60000 / (BPM * PPQ) (milliseconds).
Where BPM is the tempo of the track (Beats Per Minute).
(i.e. a 120 BPM track would have a MIDI time of (60000 / (120 * 192)) or 2.604 ms for 1 tick.
If you don't know the BPM then you'll have to determine that first. MIDI times are entirely dependent on the track tempo.
You need two pieces of information:
PPQ (pulses per quarter note), which is defined in the header of a midi file, once.
Tempo (in microseconds per quarter note), which is defined by "Set Tempo" meta events and can change during the musical piece.
Ticks can be converted to playback seconds as follows:
ticks_per_quarter = <PPQ from the header>
µs_per_quarter = <Tempo in latest Set Tempo event>
µs_per_tick = µs_per_quarter / ticks_per_quarter
seconds_per_tick = µs_per_tick / 1.000.000
seconds = ticks * seconds_per_tick
Note that PPQ is also called "division" or "ticks per quarter note" in the document linked above.
Note that Tempo is commonly represented in BPM (a frequency) but raw MIDI represents it in µs per quarter (a period).