Little buffer query

[d.healey]

I'm running a loop over a mono sample, loaded as a buffer, and I'm outputting the amplitude every 5000 samples.

But I'm getting unexpected values as I get towards the end of the sample.

Here is the waveform

And here is an example of some of the final values (in dB) I'm getting in the output.

Interface: 21201.8ms : -2.999999518003015
Interface: 21315.2ms : -2.999999518003015
Interface: 21428.6ms : -2.999999518003015
Interface: 21542ms : -2.999999518003015
Interface: 21655.3ms : -2.999999518003015
Interface: 21768.7ms : -2.999999518003015
Interface: 21882.1ms : -2.999999518003015
Interface: 21995.5ms : -2.999999518003015
Interface: 22108.8ms : -2.999999518003015

Anyone know what's going on?

	local selection = Sampler1.createSelection("");
	local stepSize = 5000;
	
	for (x in selection)
	{
		local buf = x.loadIntoBufferArray();

		for (i = 0; i < buf.length; i++)
		{
			for (j = stepSize; j < buf[i].length; j += stepSize)
			{
				Console.print(Engine.getMilliSecondsForSamples(j) + " : " + Engine.getDecibelsForGainFactor(buf[i].getMagnitude(j - stepSize, j)));
			}
		}
	}

[Christoph Hart]

@d-healey Are you reading past the array? what if buf[i].length - j < 5000?

[d.healey]

@Christoph-Hart I thought that too so tested with

Console.print(j + " : " + buf[i].length);

The last line output is:

Interface: 975000 : 976752

And since I'm never reading beyond j I think that should be good. Or perhaps I'm misunderstanding the question.

[ustk]

@d-healey this seems wrong, the second parameter numSamples should be your stepSize (protected), not the position j

Also you need to protect it when reaching the end as Chris mentioned

for (j = stepSize; j < buf[i].length; j += stepSize)
{
    local position = j - stepSize;
    local numSamples = Math.min(buf[i].length - position, stepSize); // protect
    buf[i].getMagnitude(position, numSamples);
}

And why not starting the loop at 0 to save some calculations

for (j = 0; j < buf[i].length; j += stepSize)
{
    local numSamples = Math.min(buf[i].length - j, stepSize); // protect
    buf[i].getMagnitude(j, numSamples);
}

[d.healey]

@ustk Oh, you're right, I was thinking it was start samples and end samples, but it's start samples and num samples. Now I get it, thanks!