nAudio odd buffer values from playing files

Question

The float array buffers I'm getting from nAudio seem really odd, when I replay it sounds perfect but graphing the buffer showed a picture that looked mostly like noise. It took me a while but I think I've made some headway but I'm a little stuck.

The float array that comes out has a block align of 8, so 4 floats per sample (I'm recording at 16bit so one float should easily hold this. However there are 2 and often 3 (for load) floats provided per sample. I ended up graphing it - Charts of Data. The top picture is the closest I can get to reconstructing the wave, the bottom is the wave as recorded and the middle is a chart of the raw data.

It seems to me that each float is simply holding a byte value but I'm very confused as to the first value which appears to be some kind of scaling factor.

Before I go into to much detail on what I've found I might just leave it at that with the hope Mark will know exactly how/why I am seeing this.

My current best attempt to decode this data is to convert the numbers to bytes then left shift them together which provides the top chart of the attached. I'm fairly sure that there is more to it however.

Haydan Tompkins Haydan Tompkins · Accepted Answer · 2017-01-25T00:55:56

OK so after a bit more tweaking I figured out that the float array was in fact an array of bytes from floats. Not sure if that makes sense, each "float" in the 4 floats per sample was raw bits that made up floats.

In the end this made it incredibly easy to process the buffer into an array of floats as follows;

    _samplesToProcess = floatsIn.Length / WaveFormat.BlockAlign * WaveFormat.Channels;
    if (_rawFloatsOut.Length < _samplesToProcess)
        _rawFloatsOut = new float[_samplesToProcess];

    Buffer.BlockCopy(floatsIn, 0, _rawFloatsOut, 0, floatsIn.Length);

    BufferProcessor(_rawFloatsOut);

nAudio odd buffer values from playing files

1 Answers