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Using OpenTK/OpenAL to Develop Cross Platform DIS VOIP Application

, 15 Mar 2010
Application allows voice communications (VOIP) utilizing the Distributed Interactive Simulation protocol (IEEE 1278.1)
MonoDISRadioTransmitter_SourceCode.zip
MonoDISRadioTransmitter
AudioIN
bin
Properties
StyleCop.Cache
AudioOUT
bin
Properties
DISNET
bin
DataStreams
DISPDU
Enumerations
Properties
Utilities
OpenDISRadioTransmitterExample
AudioCodecs
bin
OpenDISRadioTransmitter.csproj.user
OpenTK
OpenTK.Compatibility.dll
OpenTK.dll
OpenTK.GLControl.dll
Properties
Settings.settings
StyleCop.Cache
OpenDISRadioTransmitterSolution.suo
RadioFeatureSelection
bin
Properties
Sockets
bin
Properties
// Copyright (c) 2010, Peter Smith
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, 
// are permitted provided that the following conditions are met:
//
// Redistributions of source code must retain the above copyright notice, this list 
// of conditions and the following disclaimer. 
//
// Redistributions in binary form must reproduce the above copyright notice, this 
// list of conditions and the following disclaimer in the documentation and/or 
// other materials provided with the distribution. 
//
// Neither the name of the  Author nor the names of its contributors may be used to 
// endorse or promote products derived from this software without specific prior 
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
// IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 
// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
// OF THE POSSIBILITY OF SUCH DAMAGE.

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
    }
}

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This article, along with any associated source code and files, is licensed under The BSD License

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About the Author

pesmith
Software Developer
United States United States
No Biography provided

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