NAudio: How to accurately get the current play location when changing play position using AudioFileReader and WaveOutEvent

Question

I'm creating an application that needs to allow the user to select the play position of an audio file while the file is playing. However, once the position is changed, I'm having trouble identifying the current position.

Here's an example program that shows how I'm going about it.

using NAudio.Utils;
using NAudio.Wave;
using System;

namespace NAudioTest
{
    class Program
    {
        static void Main()
        {
            var audioFileReader = new AudioFileReader("test.mp3");
            var waveOutEvent = new WaveOutEvent();
            waveOutEvent.Init(audioFileReader);
            waveOutEvent.Play();

            while (true)
            {
                var key = Console.ReadKey(true);

                if (key.Key == ConsoleKey.Enter)
                {
                    var playLocationSeconds = 
                        waveOutEvent.GetPositionTimeSpan().TotalSeconds;
                    Console.WriteLine(
                        "Play location is " + playLocationSeconds + "seconds");
                }
                else if (key.Key == ConsoleKey.RightArrow)
                {
                    audioFileReader.CurrentTime = 
                        audioFileReader.CurrentTime.Add(TimeSpan.FromSeconds(30));
                }
                else
                {
                    break;
                }
            }
        }
    }
}

Steps to reproduce the problem

1. Start the program: the audio file starts playing
2. Press the enter key: the current play time is written to the console
3. Press the right arrow key: the played audio jumps ahead (presumably) to the expected location
4. Press the Enter key again: a play time is written to the console, but it looks to be the amount of time since the audio first started playing, not the time of the current play position.

I have tried getting the value of AudioFileReader.CurrentTime instead of calling GetPositionTimeSpan on the WaveOutEvent. The problem with this approach is that the AudioFileReader.CurrentTime value proceeds in jumps, presumably because this underlying stream is buffered when used with WaveOutEvent so CurrentTime does not accurately reflect the play position, only the position in the underlying stream.

How do I support arbitrary play positioning yet continue to get an accurate play position current time?

Answer 1

The "CurrentTime" property of your audio file reader is good enough to tell the current position of playback, especially if your latency is not very high. I found the difference between it and waveOutEvent.GetPositionTimeSpan() to be 100-200 ms. at most.

You are indeed using the setter of the CurrentTime property to reposition within the stream. It would be consistent to use the getter to then query the current position as well. If you are concerned with precision, you can use lower latency.

The extension method "GetPositionTimeSpan()" does seem to return the total length of playback so far and not the position within the stream. Admittedly I do not know why this is so.