如何生成使用FFT C ++中的音频频谱？

问题描述

我要生成的音频频谱的MP3音频文件（如看到）。基本上这个问题需要计算所述音频信号的FFT。我该怎么做我的C / C编程这++？

I want to generate an audio spectrum (as seen in this video) of a mp3 audio file. Basically this problem requires calculating the fft of the audio signal. How do I do I program this in C/C++?

我已经看了几个开源库如，我真的不知道如何使用这些用于我的问题。任何帮助将大大AP preciated。在此先感谢！

I've looked at a couple of open source libraries such as FFTW and I really don't know how to use these for my problem. Any help would be greatly appreciated. Thanks in advance!

推荐答案

有相当多的相似/相关的SO已经这是值得一读的答案包含了很多有用的信息和建议的问题，但在本质上你要做到这一点：

There are quite a few similar/related questions on SO already which are well worth reading as the answers contain a lot of useful information and advice, but in essence you need to do this:

要格式化要求的FFT
• 转换音频数据（例如INT - >浮动，独立的L / R通道）


• 申请适合（如的）


• 申请FFT（注：如果使用的输入数组的典型的复杂到复杂FFT然后设置虚部为零）


• 首先计算N / 2 FFT输出纸盒幅度（的sqrt（重*重新+ IM * IM））


• 可选转换幅度分贝（日志）规模（ 20 * log10的（大小））


• 剧情N / 2（日志）幅度值

• convert audio data to format required by FFT (e.g. int -> float, separate L/R channels)
• apply suitable window function (e.g. Hann aka Hanning window)
• apply FFT (NB: if using typical complex-to-complex FFT then set imaginary parts of input array to zero)
• calculate magnitude of first N/2 FFT output bins (sqrt(re*re + im*im))
• optionally convert magnitude to dB (log) scale (20 * log10(magnitude))
• plot N/2 (log) magnitude values

请注意，虽然FFTW是一个非常好，非常快的FFT它可能是一个有点势不可挡对于初学者 - 这也是非常昂贵的，如果你想将它作为一个商业产品的一部分 - 我建议开始的来代替。

Note that while FFTW is a very good and very fast FFT it may be a little overwhelming for a beginner - it's also very expensive if you want to include it as part of a commercial product - I recommend starting with KissFFT instead.

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