Delay sample node

Christoph Hart

This is a more or less functional delay in SNEX:

template <int NV> struct sample_delay
{
    SNEX_NODE(sample_delay);
    
    //! Type declarations
    
    // the max size for the delay
    static const int MaxBufferSize = 128;
    // we assume stereo operation
    static const int NumChannels = 2;
    
    // a stereo frame (just two float numbers next to each other)
    using FrameData = span<float, NumChannels>;
    
    // a fixed size buffer type for MaxBufferSize frames
    using DelayBufferType = span<FrameData, MaxBufferSize>;
    
    // A index type that will wrap around its upper limit
    using IndexType = index::wrapped<MaxBufferSize>;
    
    //! Member variables
    DelayBufferType buffer;
    IndexType readBuffer;
    IndexType writeBuffer;
    
    // Reset the processing pipeline here
    void reset()
    {
        // clear the buffer
        for(auto& frame: buffer)
            for(auto& s: frame)
                s = 0.0f;
                
        // set the write buffer offset (= delay) to any value
        writeBuffer = 50;
    }
    
    void processFrame(FrameData& d)
    {
        // write the current frame to the buffer
        buffer[++writeBuffer] = d;
        
        // read from the read position (behind the write position)
        d = buffer[++readBuffer];
    }
    
    // A dummy method if you call it with 1 channel
    void processFrame(span<float, 1>& data) {}
    
    template <typename ProcessDataType> void process(ProcessDataType& data)
    {
        // Create a FrameProcessor from the process data
        auto fp = data.toFrameData();
        
        // iterate over the frames and call processFrame above
        while(fp.next())
            processFrame(fp.toSpan());
    }
    
    // Unused callbacks...
    
    void prepare(PrepareSpecs ps) {}
    void handleHiseEvent(HiseEvent& e) {}
    void setExternalData(const ExternalData& d, int index) {}
    template <int P> void setParameter(double v) {}
};

I'll leave it as excercise for the reader to make the delay time a parameter :)

ustk

@Christoph-Hart Oh great I'll study this with attention!
And what if I use a frame1_block with send/receive? It seems that the signal is then received a sample later right?

Christoph Hart

If the receive node is before the send node, then yes, there will be a delay of a single sample.

orange

I can't get decimal value sample delay with Simple Gain Delay (with using getMilliSecondsForSamples) and Latency Compensation. For sample delay, only integer values are working.

For example, there is no difference between 2.2 and 2.4 sample delay. Hise applies 2 samples on both of them. Am I missing something?

ustk

@orange delay can only be multiples of one sample. Any ms value is rounded to the nearest sample, so the opposite is only integer samples can be computed to decimal ms for a given samplerate.
Or in other words, a system cannot compute between samples since it is the lowest discrete value.
That been said, if you need more precision, then you should consider oversampling in scriptnode and set the delay in there. (But I am not sure in the end this will be delayed of the amount you set in the oversampled container when going back to the original samplerate world)

Christoph Hart

@orange What you need is a interpolating delay line, then you can delay by non-integer sample values. There is a index type in SNEX which offers interpolation.

It's actually used in the PitchShifter example (which also needs a varying interpolating delay line for the Doppler effect):

https://github.com/christophhart/hise_tutorial/blob/77ed71405fd1d5a9cdfd9b827637bc666d3a35f4/PitchShifting/DspNetworks/CodeLibrary/snex_node/PitchShifter.h#L58

orange

I will check it out, thanks guys!

ustk

@Christoph-Hart So is your example a good start for designing filters? If I mix pre and post delay with coefficients...
Or is there a "node only" way for the novice?

ustk

@Christoph-Hart Hmm... I just copied/pasted your sample delay script above in a SNEX file and this is what I get:

Christoph Hart

I think you have to name the snex file exactly lile the class, so sample_delay.

However I think I need to think about a better way of quickly sharing examples, something like the HiseSnippet function for SNEX - currently all Snex code management is file based.

ustk

@Christoph-Hart Thanks this seems to work...

And what is the purpose of the clickable SNEX logo?
At first, I thought it would call a code editor, but apparently, we can only edit the SNEX file externally right?
So when we edit and save a SNEX file, does Hise automatically handle the update without restarting?

Christoph Hart

If your in the workbench you can edit the snex node code when you press the snex button but I have no idea what it does in HISE lol.

ustk

@Christoph-Hart :)
I think I might more often use SNEX from within Hise than the workbench at least for little things. Or maybe we can work in both at the same time, then each time you save in the workbench Hise takes the update into account...

Delay sample node

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