render audio in background?

[ulrik]

Is it possible to set a function to push buffers through modules silently in the background?

Lets say I have an audio buffer, can I let it through different effects, nodes silently in the background, and then store the processed buffer and write to an audio file?

[HISEnberg]

@ulrik I haven't tried pushing audio to a separate thread, my understanding is pretty limited but it should, hypothetically, be possible.

The BackgroundTask API is certainly what you would want to use for this. I may be working on this exact topic in a few weeks so let me know if you make any progress with it!

[Christoph Hart]

@ulrik There are multiple ways to achieve this, the most fun one is this here:

• a scriptnode network with a split container that provides a "silent processing chain" by adding a clear node at the start and the end
• two audio file slots, the first is connected to a file player and a file analyzer.
• the second is connected to a recorder node
• the file analyser sends the length of the loaded file of the first slot to the length parameter of the recorder note and starts the playback and recording
• you can add whatever DSP processing you want between the file player and the recorder.
• once the file player is done, the recorder will save the incoming audio into a new buffer
• we can then register the content callback of the second slot to flush the recording. pick and save a file, clear out the first audio file slot.

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[ulrik]

@Christoph-Hart that sounds great, I will study your example, thanks!

[ulrik]

@Christoph-Hart This works great!
If I set a stretch node instead of the "file player" node, I am able to pitch shift the original audio, nice!
If I change the time ratio on the stretch player, I am also getting a time stretched result, however I need to change the "recording length" dependent on the time ratio.
Now the file analyser provides me with the original length of the audio file, is there a way to modify the recording length related to the time ratio set in the stretch player?

[ulrik]

@ulrik never mind, I found out, I need to scale the length coming from the file analyzer with the time ratio value, and set it to the recorder.
Using a pma node will fix that I guess

[ulrik]

@ulrik said in render audio in background?:

@ulrik I need to scale the length coming from the file analyzer ...

That was harder than I thought.
I set it up like this:

Using the min max node to invert the TimeRatio value and feed that into the pma Multiply.
That is working if I can find the exact Skew value on the min max node.
As it is now I have set the skew to 0.65, and it's close.

Is it possible to find the exact skew value considering the TimeRatio range 0.5 => 2.0

[Christoph Hart]

@ulrik Right click on the stretch player's time ratio parameter and you'll see this:

Here it is as a number so you don't have to do it yourself:

0.6309297680854797

[ulrik]

@Christoph-Hart perfect, thanks!

One more question, when I render the buffer through the stretch node, there is latency baked into the resulting file (there is a small part at the beginning which is silent), is there a way to find out how many samples that is?
I'm thinking of adding the silent length to the resulting buffer and then trim the start, is that a proper way to get rid of it?

[Christoph Hart]

@ulrik yeah there are tools in the Buffer API:

HISE | Scripting | Buffer

A buffer of floating point data

(docs.hise.dev)

• getNextZeroCrossing() should give you the first non-zero value (haven't checked that though), otherwise it's trivially to implement this with a loop
• trim() can be used to create a buffer from a sub range of an existing buffer, this is the most efficient way.

[ulrik]

@Christoph-Hart thanks a lot!