Conversion from Mp3 to Wav offsets the output audio

[WTTSoftwareSolutions]

When converting an Mp3 to Wav using NAudio 2.10 (and previous versions) the wav file output is longer in length and there seems to be padding added at the beginning, which offsets the actual start of the audio.

using NAudio.Wave;

var outFile = @"C:\Temp\NAudioMP3Test\NAudioTestWAV.wav";
var inFile = @"C:\Temp\NAudioMP3Test\NAudioTestMP3.mp3";

using (var reader = new AudioFileReader(inFile)) {
    try {
        WaveFileWriter.CreateWaveFile(outFile, reader);
    } catch (Exception ex) {
        Console.WriteLine(ex.Message);
    }
}

[markheath]

This may be inevitable with MP3 - it encodes blocks of audio so the output will not be the exact same length. I expect you'll get a similar result with other tools.

[WTTSoftwareSolutions]

I can convert mp3 to wav in Audacity and it is the same length.
I have tried most of the .NET C# solutions including NLayer and MP3Sharp and reading the mp3 always adds the padding.
As far as encoding, NAudio.Lame works perfect. The output mp3 is a match to the input audio.
This would normally not be an issue except we are not generating the mp3 output for listening enjoyment, we are striping one channel of the audio with SMPTE or FSK timecode. The offset is a huge issue with the timecode and the choreography that was done to the original audio.
At this point, I'm at a complete loss. Might have to disable support for mp3.

[markheath]

Can you try with both MediaFoundationReader and Mp3FileReader instead of AudioFileReader - do they produce different results

[WTTSoftwareSolutions]

I tried both and got the same results. I initially thought that using MediaFoundationReader would solve the issue, but it gave me the same issue as Mp3FileReader.
I had briefly looked at what Audacity is using, libmad, but trying to port that to C# was outside the scope of my skills (very rudimentary understanding of C/C++)

[markheath]

OK, I suspect that means that the MP3 decoders included with Windows are introducing the delay.
Two other suggestions for you - (1) you can try plugging NLayer into Mp3FileReader as the decoder. (2) just make a command-line call to FFMPEG.exe if that's possible - I tend to use that a lot these days for converting between various formats

[WTTSoftwareSolutions]

To solve the mp3 decoding issue, I've created an FFMpegMp3Reader which makes use of FFmpeg.NET. Internally this creates a temp PCM wav file on disk and then reads the temp file in with WaveFileReader.
For the encoding issues, I use NAudio.Lame to write the mp3 output.