Using OpenTK/OpenAL to Develop Cross Platform DIS VOIP Application

// Copyright (c) 2010, Peter Smith
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namespace AudioOUT
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading;

    using OpenTK;
    using OpenTK.Audio;
    using OpenTK.Audio.OpenAL;

    public class PlayAudio
    {
        #region Fields

        ALError alError;
        AudioContext audio_context;
        private Vector3 position = new Vector3();

        //The use of two sources was added do to problems found when transmitting voice continuously (ie. PTT activated for long periods of time)
        //There was a delay in the sound after a period of time.  This occurence only seemed to happen on a Windows system as
        //the linux (SUSE) seemed to keep up with the sound.  I have seen this also in other applications i have created using
        //the Win32 waveOutOpen function. Therefore the use of two sources. There is potential for voices to run ontop of each other but due to the
        //serial nature of the sound comming in I do not believe this will occur.
        private int[] sources = new int[2];
        private int sourcesLeft = 0;

        #endregion Fields

        #region Constructors

        /// <summary>
        /// Initialize playback of audio
        /// </summary>
        public PlayAudio()
        {
            IList<string> availableDevices = AudioContext.AvailableDevices;

            foreach (string item in availableDevices)
            {
                string availablePlaybackDevices = item;
            }

            audio_context = new AudioContext();
            
            //Initialize the sources
            for (int i = 0; i < sources.Length; i++)
            {
                sources[i] = AL.GenSource();
            }

            position = SetSpeakerPosition(SpeakerLocation.LeftRight);
        }

        #endregion Constructors

        #region Enumerations

        /// <summary>
        /// Location of speaker output
        /// </summary>
        public enum SpeakerLocation
        {
            Left,
            Right,
            LeftRight
        }

        #endregion Enumerations

        #region Methods

        /// <summary>
        /// Playback the audio
        /// </summary>
        /// <param name="unencodedData">Raw byte data</param>
        /// <param name="recordingFormat">OpenAL sound format</param>
        /// <param name="sampleFrequency">Frequency of the samples</param>
        /// <param name="speakerLocation">Speaker location</param>
        public void PlayBackAudio(byte[] unencodedData, ALFormat recordingFormat, int sampleFrequency, SpeakerLocation speakerLocation)
        {
            //Determine if sources needed to be switched
            if (sourcesLeft == 0)
            {
                sourcesLeft = sources.Length;
            }

            //Used to rotate the sources being used.
            sourcesLeft--;

            int buf = AL.GenBuffer();

            AL.BufferData(buf, recordingFormat, unencodedData, unencodedData.Length, sampleFrequency);

            position = SetSpeakerPosition(speakerLocation);
            AL.Source(sources[sourcesLeft], ALSource3f.Position, ref position);

            AL.SourceQueueBuffer(sources[sourcesLeft], buf);
            if (AL.GetSourceState(sources[sourcesLeft]) != ALSourceState.Playing)
            {
                ClearSourcePlayBackBuffers(sources[sourcesLeft]);
                AL.SourcePlay(sources[sourcesLeft]);
            }

            ClearSourcePlayBackBuffers(sources[sourcesLeft]);
        }

        /// <summary>
        /// Playback a file
        /// </summary>
        /// <param name="unencodedData">Raw byte data</param>
        /// <param name="recordingFormat">Format of data</param>
        /// <param name="sampleFrequency">Frequency sampling of data</param>
        public void PlayFile(byte[] unencodedData, ALFormat recordingFormat, int sampleFrequency)
        {
            int[] uiBuffers = new int[4];
            int uiSource;

            uiBuffers = AL.GenBuffers(uiBuffers.Length);

            uiSource = AL.GenSource();

            alError = AL.GetError();

            AL.BufferData(uiBuffers[0], recordingFormat, unencodedData, unencodedData.Length, sampleFrequency);

            alError = AL.GetError();

            AL.SourceQueueBuffers(uiSource, 1, uiBuffers);

            alError = AL.GetError();
            AL.SourcePlay(uiSource);

            alError = AL.GetError();
        }

        /// <summary>
        /// Stop Audio playback
        /// </summary>
        public void StopPlayBack()
        {
            for (int i = 0; i < sources.Length; i++)
            {
                StopPlayBack(sources[i]); 
            }

            audio_context.Dispose();
        }

        /// <summary>
        /// Stop Audio playback
        /// </summary>
        private void StopPlayBack(int src)
        {
            if (audio_context != null)
            {
                AL.SourceStop(src);
                ClearSourcePlayBackBuffers(src);
            }
        }

        /// <summary>
        /// Clear the buffers from the selected source
        /// </summary>
        /// <param name="source">Source buffer to clear</param>
        private void ClearSourcePlayBackBuffers(int source)
        {
            int BuffersProcessed;
            int[] freedbuffers;
            AL.GetSource(source, ALGetSourcei.BuffersProcessed, out BuffersProcessed);
            if (BuffersProcessed == 0)
                return;

            freedbuffers = AL.SourceUnqueueBuffers(source, BuffersProcessed);

            AL.DeleteBuffers(freedbuffers);
        }


        private Vector3 SetSpeakerPosition(SpeakerLocation speakerLocation)
        {
            Vector3 location = new Vector3();

            if (speakerLocation == SpeakerLocation.LeftRight)
            {
                location = new Vector3(1, 0, 1);
            }

            if (speakerLocation == SpeakerLocation.Left)
            {
                location = new Vector3(-1, 0, 0);
            }

            if (speakerLocation == SpeakerLocation.Right)
            {
                location = new Vector3(1, 0, 0);
            }

            return location;
        }

        #endregion Methods
    }
}