Timestretch tempo sync, Num Quarters question

[d.healey]

I have a tremolo sample that was recorded at 140BPM. The sample is 4 bars long followed by quite a long release tail. I've set a loop in the sample from bar 2 to bar 4.

What should I set NumQuarters to for the tempo sync time stretch mode?

Why can't I just tell it the BPM is 140?

[VirtualVirgin]

@d-healey What is the NumQuarters an argument for? I don't know what math you need without more context. Are you assuming 4/4 bars?

[d.healey]

@VirtualVirgin I have no idea, this is what it says in the docs

NumQuarters double 0.0 if this is not 0.0, it will skip the automatic detection of the sample length when in tempo-synced mode and use this value to determine the BPM of the source sample (so you will need to set this to the value of your loop lengths).

[VirtualVirgin]

@d-healey It sounds like you just need to calculate the number of quarter notes in your loop.
You said a loop from bar 2 to 4? So a 2 bar loop? In 4/4?
NumQuarters = bars * beats
That's 4 quarters per bar, so your "NumQuarters" should be 8.

Though is the timestretch for the whole sample length?
Then I guess you would want 4x4, so NumQuarters = 16.

[d.healey]

@VirtualVirgin said in Timestretch tempo sync, Num Quarters question:

It sounds like you just need to calculate the number of quarter notes in your loop.

If it was that simple I'd be very happy. It was the first thing I've tried, I tried a bunch of others too.

I think that documentation must assume that the sample is only as long as the loop, from start to finish. As I said my sample is very long - long release tail, and the looped part doesn't start until bar 2. So while the loop is only 8 quarter notes, that won't provide the BPM of the whole file.

[VirtualVirgin]

@d-healey Can you edit your release tail to end on a specific beat (add space)? If so, maybe you could calculate the total beats from that.

[d.healey]

@VirtualVirgin I don't think that would work because the loop is still only going to be 2 bars.

[VirtualVirgin]

@d-healey But isn't the whole thing getting timestrethced?

[d.healey]

@VirtualVirgin Yes, but each sample is a different length - higher notes have a shorter tail than lower notes. So putting in the total length won't work even if it is right for one sample - which I just tested and it doesn't work, the stretch ratio is completely wrong.

@Christoph-Hart Any input on this?

[Chazrox]

@d-healey Would it be hard to impliment warping points based on transients marked by the user? Thats how its done in Abelton live. The algorithm I assume is using the math between those markers to calculate timestretching.

idk f this helps but this is what I use to get some math out of it when im working...

this is the beat increments in /ms @140 bpm.

Im surrre with this math you should be able to come up with something. I've seen you guys do some crazy stuff.

My guess is the match per beat in between bars (in /ms) needs to be stretched to target tempo (in /ms).

Im not a coder at all and I could be speaking redundantly but this is my thought process as a music producer.

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[Chazrox]

Here's the chart @ 160bpm...

so the quarter note length @ 140bpm just needs to be calculated to match the note length @160bpm.

[d.healey]

@Chazrox said in Timestretch tempo sync, Num Quarters question:

Would it be hard to impliment warping points based on transients marked by the user?

Probably very hard - no idea - but not necessary for this issue. My samples were recorded to a fixed 140bpm click, it doesn't vary.

I just had an idea though. I could forget about the tempo sync mode and use the time variant mode myself and do my own calculation of the pitch ratio - worth a try anyway.

[Chazrox]

@d-healey well besides making a new feature in HISE, this is pretty much what I mean. These values are what you need. I've seen you guys do similar calculations before. I believe you can do it!

[d.healey]

@Chazrox said in Timestretch tempo sync, Num Quarters question:

These values are what you need.

I don't see how they are applicable in this situation.

[d.healey]

Ok here's the solution - well it doesn't answer my question but it gets the job done.

const var Sampler1 = Synth.getSampler("Sampler1");

const th = Engine.createTransportHandler();

th.setOnTempoChange(true, updateTimeStretchRatio);

// fetch the current state
const var obj = Sampler1.getTimestretchOptions();

// Apply your changes
obj.SkipLatency = true;

// Update the options
Sampler1.setTimestretchOptions(obj);

inline function updateTimeStretchRatio(newTempo)
{
	local ratio = newTempo / 140;
	Sampler1.setTimestretchRatio(ratio);			 
}