PCMReader returning wrong fileDurationMs on 8 bit converted audio

[peterdaub]

Thanks for the library by the way, it's been super helpful!

If a file is 8bit, the PCMReader will properly convert to 16bit PCM. However, the PCMReader.getFileDurationMs method is calculating the duration based off the file size of the 8bit file but the frameSize and frameRate of the converted AudioFormat.

That method should use the encoded format instead of the decoded format to get the duration. The result is a final FFT with an incorrect number results by about half.