Audio-Router/Audio Router UWP/Audio Router/MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
using Windows.Devices.Enumeration;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.Media;
using Windows.Media.Audio;
using Windows.Media.Capture;
using Windows.Media.Devices;
using Windows.Media.Playback;
using Windows.Media.Render;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Documents;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace Audio_Router
{
    
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        //AudioGraph graph;
        // The list of audio devices
        DeviceInformationCollection sourceDevices;
        DeviceInformationCollection targetDevices;
        public MainPage()
        {
            this.InitializeComponent();

            App.appRef.Suspending += AppRef_Suspending;
            App.appRef.Resuming += AppRef_Resuming;
            App.appRef.EnteredBackground += AppRef_EnteredBackground;
            App.appRef.LeavingBackground += AppRef_LeavingBackground;
        }

        private void AppRef_LeavingBackground(object sender, Windows.ApplicationModel.LeavingBackgroundEventArgs e)
        {
            if (IsLoaded)
            {
                BackgroundRestore();
            }
            
        }

        private void AppRef_EnteredBackground(object sender, Windows.ApplicationModel.EnteredBackgroundEventArgs e)
        {
            BackgroundCleanup();
        }

        private void AppRef_Resuming(object sender, object e)
        {
            BackgroundRestore();
        }

        /// <summary>
        /// Clear existing elements from this display, to free memory
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void AppRef_Suspending(object sender, Windows.ApplicationModel.SuspendingEventArgs e)
        {
            BackgroundCleanup();
        }


        private void BackgroundCleanup()
        {
            // Clear all items from the lists
            InputAudioComboBox.Items.Clear();
            OutputAudioComboBox.Items.Clear();
            CreatedGraphs.Children.Clear();
            // Ensure the GC collects freed memory, by explicitly calling the GC
            GC.Collect();
        }

        private void BackgroundRestore()
        {
            // Start the task that populates the lists
            if (InputAudioComboBox.Items.Count > 0 || OutputAudioComboBox.Items.Count > 0) return;
            _ = Task.Run(() => FindAudioSources());
            // And add existing graphs back to the page
            foreach (AudioGraphConnection graphConneciton in App.appRef.audioGraphConnections)
            {
                Grid renderGrid = graphConneciton.GetAsDisplayItem(out Button visualButton);
                CreatedGraphs.Children.Add(renderGrid);
                void handler(object sender, RoutedEventArgs e)
                {
                    visualButton.Click -= handler;
                    DestroyVisualElement(ref renderGrid);
                }
                visualButton.Click += handler;
            }
        }
        /// <summary>
        ///  When the page is navigated to, populate the list
        /// </summary>
        /// <param name="e"></param>
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            // Populate audio device list; as a Task to avoid delaying creation
            _ = Task.Run(() => FindAudioSources());
            
        }
        
        private async Task FindAudioSources()
        {
            // First, clear the lists
            _ = Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                InputAudioComboBox.Items.Clear();
                OutputAudioComboBox.Items.Clear();
            });
            // Perform this on our spawned thread, as the operation is asynchronous-synchronous await
            sourceDevices = await DeviceInformation.FindAllAsync(MediaDevice.GetAudioCaptureSelector());
            targetDevices = await DeviceInformation.FindAllAsync(MediaDevice.GetAudioRenderSelector());

            DeviceInformation defaultOutput = await DeviceInformation.CreateFromIdAsync(MediaDevice.GetDefaultAudioRenderId(AudioDeviceRole.Default));
            DeviceInformation defaultInput = await DeviceInformation.CreateFromIdAsync(MediaDevice.GetDefaultAudioCaptureId(AudioDeviceRole.Default));

            _ = Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                // Set the Input device
                for (int i = 0; i < sourceDevices.Count; i++)
                {
                    if (sourceDevices[i].Id == defaultInput.Id)
                    {
                        InputAudioComboBox.Items.Add(sourceDevices[i].Name + " (Default Device)");
                        InputAudioComboBox.SelectedIndex = i;
                    }
                    else
                    {
                        InputAudioComboBox.Items.Add(sourceDevices[i].Name);
                    }
                }

                // Set output device & add to inputs too
                for (int i = 0; i < targetDevices.Count; i++)
                {
                    if(targetDevices[i].Id == defaultOutput.Id)
                    {
                        OutputAudioComboBox.Items.Add(targetDevices[i].Name + " (Default Device)");
                        OutputAudioComboBox.SelectedIndex = i;
                    }
                    else
                    {
                        OutputAudioComboBox.Items.Add(targetDevices[i].Name);
                    }
                }
            });
        }

        private async void startStreamButton_Click(object sender, RoutedEventArgs e)
        {
            await CreateAudioGraph();
        }

        private async Task CreateAudioGraph()
        {
            App.displayRequest.RequestActive();
            DeviceInformation outputDevice = targetDevices[OutputAudioComboBox.SelectedIndex];
            DeviceInformation inputDevice = sourceDevices[InputAudioComboBox.SelectedIndex];
            AudioGraphSettings settings = LowLatencyCheckbox.IsChecked == true
                ? new AudioGraphSettings(AudioRenderCategory.Media)
                {
                    QuantumSizeSelectionMode = QuantumSizeSelectionMode.ClosestToDesired,
                    DesiredSamplesPerQuantum = 10,
                    PrimaryRenderDevice = outputDevice,
                    DesiredRenderDeviceAudioProcessing = Windows.Media.AudioProcessing.Raw,
                    EncodingProperties = new Windows.Media.MediaProperties.AudioEncodingProperties()
                    {
                        Subtype = "Float",
                        SampleRate = 128000, // Manually set to 128 000 samples/second so that the delay is significantly reduced
                        ChannelCount = 2,
                        BitsPerSample = 32,
                        Bitrate = 3072000
                    }
                }
                : new AudioGraphSettings(AudioRenderCategory.Media)
                {
                    PrimaryRenderDevice = outputDevice
                };
            CreateAudioGraphResult result = await AudioGraph.CreateAsync(settings);
            AudioGraph ag = result.Graph;

            if (result.Status != AudioGraphCreationStatus.Success)
            {
                return;
            }

            CreateAudioDeviceInputNodeResult deviceInputNodeResult = await ag.CreateDeviceInputNodeAsync(MediaCategory.Other, ag.EncodingProperties, inputDevice);

            if (deviceInputNodeResult.Status != AudioDeviceNodeCreationStatus.Success)
            {
                // Fail-safe, switch to using the default encoding properties
                settings = new AudioGraphSettings(AudioRenderCategory.Media)
                {
                    PrimaryRenderDevice = outputDevice
                };
                result = await AudioGraph.CreateAsync(settings);
                ag = result.Graph;
                if (result.Status != AudioGraphCreationStatus.Success)
                {
                    return;
                }
                deviceInputNodeResult = await ag.CreateDeviceInputNodeAsync(MediaCategory.Other, ag.EncodingProperties, inputDevice);
                if (deviceInputNodeResult.Status != AudioDeviceNodeCreationStatus.Success)
                {
                    return;
                }
            }

            // Create the device output node connection
            CreateAudioDeviceOutputNodeResult deviceOutputNodeResult = await ag.CreateDeviceOutputNodeAsync();
            if (deviceOutputNodeResult.Status != AudioDeviceNodeCreationStatus.Success)
            {
                return;
            }
            deviceInputNodeResult.DeviceInputNode.AddOutgoingConnection(deviceOutputNodeResult.DeviceOutputNode);
            // appMediaControls.PlaybackStatus = MediaPlaybackStatus.Playing;
            ag.Start();
            AudioGraphConnection graphConnection = new AudioGraphConnection(ag, deviceOutputNodeResult.DeviceOutputNode, deviceInputNodeResult.DeviceInputNode, Dispatcher);
            App.appRef.audioGraphConnections.Add(graphConnection);

            // Hold a reference to the created button; when clicked we must also ensure we remove this visual element from the grid display
            Grid renderGrid = graphConnection.GetAsDisplayItem(out Button visualButton);
            CreatedGraphs.Children.Add(renderGrid);
            // Inline decl to add a second listener to the click event - will remove the grid from the display
            void handler(object sender, RoutedEventArgs e)
            {
                visualButton.Click -= handler;
                DestroyVisualElement(ref renderGrid);
            }
            visualButton.Click += handler;
        }

        private void DestroyVisualElement(ref Grid element)
        {
            _ = CreatedGraphs.Children.Remove(element);
            element = null;
        }
    }    
}