JUCE resampler

[peter.semiletov]

Hello! I’m completely stuck with the JUCE interpolators
Before that I used libsamplerate and I was happy.
I need to resample the buffer of floats from sound file’s samplerate to DAW session’s sample rate.
So I have the source buffer (loaded from the reader):

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juce::AudioBuffer<float> *buffer = new juce::AudioBuffer<float>;

If the buffer’s samplerate != session’s samplerate I need to resample.
My steps are.

Define the resamling ratio:

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float ratio = (float) session_samplerate / samplerate;

Calculate the output frames (samples) count for each channels:

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size_t output_frames_count = ratio * length_in_samples;

length_in_samples is the length of the source buffer, in samples, for the any of the channels.

I define the new buffer to write resampled data:

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juce::AudioBuffer<float> * output_buffer = new juce::AudioBuffer <float> (channels, output_frames_count);

Then I process:

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 for (int i = 0; i < channels; i++)
      {
       juce::LinearInterpolator interpolator;

    int result = interpolator.process (ratio,
                                        buffer->getReadPointer(i),
                                        output_buffer->getWritePointer(i),
                                        output_frames_count);
}

Sometime it works, but sound sounded as doubled/repeated, sometime I get just crashes..

[tseaver]

Ob. disclaimer: I haven't done serious C / C++ development for years. Nevertheless, perhaps this might help:

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float ratio = (float) session_samplerate / samplerate;

You might want to coerce both values before dividing, e.g.:

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float ratio = ((float) session_samplerate) / ((float) samplerate);

Given that you are sometimes seeing crashes, rather than just mis-resampled values, my change won't likely fix anything.

[peter.semiletov]

Thank you! But it does not help Actually, I started to use Speex resampler instead.

[SocaLabs]

LinearInterpolator has state, so you can't recreate it every time around the loop, it needs to be a member variable, and you need one per channel.

If you are getting crashes, maybe yo are reading off the end of your input buffer. There is another version of process where you also feed in remaining number of source samples.

[peter.semiletov]

Finally, I took the resampler from Speex, it works in a same way as libsamplerate )