bugfix: AudioFile<double> not properly saved to 32-bit (IEEE floating-point) WAV

[gitelope]

Fixes issue (#96) with saving AudioFile<double> to 32-bit WAV producing loud, scratchy noise.

[adamstark]

Hi there, thank you for this. Do you think you'd be able to provide a bit of sample code that produces the issue?

This is not because I don't believe your experience - simply I just want to write a unit test to capture this problem and then demonstrate that the change fixes it. I tried writing a test myself but could re-create the problem (perhaps I don't understand entirely the use case).

Thanks!

[Dwebb22]

Have to wait til next month. Until then, let's talk about flux.

…

On Fri, May 23, 2025, 12:56 AM Adam Stark ***@***.***> wrote: *adamstark* left a comment (adamstark/AudioFile#97) <#97 (comment)> Hi there, thank you for this. Do you think you'd be able to provide a bit of sample code that produces the issue? This is not because I don't believe your experience - simply I just want to write a unit test to capture this problem and then demonstrate that the change fixes it. I tried writing a test myself but could re-create the problem (perhaps I don't understand entirely the use case). Thanks! — Reply to this email directly, view it on GitHub <#97 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AOEGDMUAC2W7QM4MQF6CJIL273IEBAVCNFSM6AAAAAB42SCPUCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSMBTGU4TSNJWGI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[gitelope]

MAKE SURE TO READ VOLUME WARNING AT END OF COMMENT.

constexpr int channels {1};
constexpr int sampleRate {48000};
constexpr int bitDepth {32};

constexpr double lengthInSeconds {1};
constexpr double frequency {440};

constexpr int lengthInSamples = sampleRate * lengthInSeconds;

AudioFile<double> af;

af.setSampleRate (sampleRate);
af.setBitDepth (bitDepth);
af.setAudioBufferSize (channels, lengthInSamples);

for (int n=0; n<lengthInSamples; ++n)
    af.samples[0][n] = sin (2. * M_PI * frequency * static_cast<double>(n) /sampleRate);

// This may be VERY LOUD:
af.save("lower-your-volume-as-far-as-possible.wav");

If instead I use
AudioFile<float> af;
there's no issue.

The audio is actually quite loud for me so I recommend turning your volume as down as far as you can without turning it off and listening with some cheap headphones or speakers and get ready to mute or pause or something.

[adamstark]

Thanks for this! I managed to write some unit tests that failed by doing some 32-bit and double precision tests. I've also confirmed your change fixes the problem, nice work! :)

I'll merge this into develop now...