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Display images in UWA that is not from App Assets

I've some hard time trying to display images in my UWP App.
My images are located in the Images library.
The question is:
How to show jpg in the Image Xaml control on a UWP, that is not in the projects "Assets"?
So far using Binding, I’ve
Try to set Image.Source to the full path with no success, image control remains blank. (for file access retriction a guess)
Try using setting BitMapImage to the Image.Source property with no success, image control remains blank. (for file access retriction a guess)
Try to assign FileStorage class to the Image.Source property with no success, image control remains blank.
Try to load the image file in a stream and load the stream in the BitmapImage, but there I’ve threading issues. More about this below.
About the threading issue, I’ve come to two issues for now.
When loading the file/stream:
var file = File.ReadAllBytes(_currentImagePath);
I get
System.InvalidOperationException: 'Synchronous operations should not be performed on the UI thread. Consider wrapping this method in Task.Run.'
When using Task.Run on any manner I get an exception when trying to set the Bitmap source
The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD))
var bitmap = new BitmapImage();
return await Task.Run(async () =>
{
var file = File.ReadAllBytes(_currentImagePath);
using (var stream = new InMemoryRandomAccessStream())
{
await stream.WriteAsync(file.AsBuffer());
stream.Seek(0);
await bitmap.SetSourceAsync(stream); // **Exception here**
return bitmap;
}
});
Here the full source code:
namespace App1.Images
{
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
using Windows.Storage;
using Windows.Storage.Streams;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Media.Imaging;
using App1.Annotations;
public class ImagesLibrairies : INotifyPropertyChanged
{
private readonly HashSet<Image> _images;
private readonly string _fileTypes;
private readonly HashSet<Image> _preferrednessFiles;
private readonly DispatcherTimer _timer;
private ulong _minFileSize = 5 * 1024; // 5k in bytes
private ulong _maxFileSize = 1024 * 1024 * 20; //20 MBytes
private int _imageIndex = 0;
public ImagesLibrairies()
{
_preferrednessFiles = new HashSet<Image>();
_fileTypes = "*.jpg;*.jpeg;*.bmp;*.tif"; // ignore *.ico;*.png;*.svg;*.gif
_images = new HashSet<Image>();
_timer = new DispatcherTimer { Interval = new TimeSpan(0, 0, 0, 5) };
_timer.Tick += _timer_Tick;
}
private Uri _currentImage;
public Uri CurrentImage
{
get => _currentImage;
private set
{
_currentImage = value;
OnPropertyChanged(nameof(CurrentImage));
OnPropertyChanged(nameof(Image));
}
}
public async Task<BitmapImage> GetBitmapImage()
{
var bitmap = new BitmapImage();
return await Task.Run(async () =>
{
var file = File.ReadAllBytes(_currentImagePath);
using (var stream = new InMemoryRandomAccessStream())
{
await stream.WriteAsync(file.AsBuffer());
stream.Seek(0);
await bitmap.SetSourceAsync(stream);
return bitmap;
}
});
}
public BitmapImage Image
{
get
{
if (!string.IsNullOrEmpty(_currentImagePath))
return GetBitmapImage().Result;
return null;
}
}
private string _currentImagePath;
public string CurrentImagePath
{
get => _currentImagePath;
set
{
_currentImagePath = value;
OnPropertyChanged(nameof(CurrentImagePath));
CurrentImage = new Uri(value);
}
}
public object CurrentStorageFile { get; set; }
private void _timer_Tick(object sender, object e)
{
SetNext();
}
public async Task ScanLibrairies()
{
var picturesFolder = KnownFolders.PicturesLibrary;
var files = await picturesFolder.GetFilesAsync();
foreach (var file in files)
{
Debug.WriteLine(file.Name + ", " + file.DateCreated);
if (_images.Count >= int.MaxValue)
return;
var prop = await file.GetBasicPropertiesAsync();
var imageLocation = new Image
{
StorageFile = file,
Properties = prop
};
if (imageLocation.Properties.Size < _minFileSize || imageLocation.Properties.Size > _maxFileSize)
continue;
if (_preferrednessFiles.Any(o => o.Equals(imageLocation) && o.Preferredness == Preferredness.No))
continue;
_images.Add(imageLocation);
}
}
public void SetNext()
{
if (_images == null || !_images.Any())
{
return;
}
_imageIndex++;
var image = _images.Skip(_imageIndex).FirstOrDefault();
if (image != null)
{
Debug.WriteLine($"Displaying: {image.StorageFile.Path}");
}
CurrentImagePath = image?.StorageFile.Path;
CurrentImage = new Uri(CurrentImagePath);
}
public void SetPrevious()
{
if (_images == null || !_images.Any())
return;
_imageIndex--;
var image = _images.Skip(_imageIndex).FirstOrDefault();
CurrentImagePath = image?.StorageFile.Path;
}
public void LikeThisPicture(Image picture)
{
var pic = _preferrednessFiles.FirstOrDefault(o => o.Equals(picture));
if (pic == null)
{
picture.Preferredness = Preferredness.Very;
_preferrednessFiles.Add(picture);
return;
}
pic.Preferredness = Preferredness.Very;
}
public void DislikeThisPicture(Image picture)
{
var pic = _preferrednessFiles.FirstOrDefault(o => o.Equals(picture));
if (pic == null)
{
picture.Preferredness = Preferredness.No;
_preferrednessFiles.Add(picture);
return;
}
pic.Preferredness = Preferredness.No;
}
public void StartAsync()
{
ScanLibrairies();
_timer.Start();
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Here the xaml markup
<Page.DataContext>
<images:ImagesLibrairies/>
</Page.DataContext>
<Grid >
<!--Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">-->
<Image Stretch="UniformToFill" Margin="15">
<Image.Source>
<BitmapImage UriSource="{Binding Image}"></BitmapImage>
<!--<BitmapImage UriSource="{Binding CurrentImagePath}"></BitmapImage>-->
<!--<BitmapImage UriSource="D:\Utilisateurs\hugod\OneDrive\Images\jouets\20180106_132041.jpg"></BitmapImage>-->
<!--<BitmapImage UriSource="Assets/Black-And-White-Wall-Brick-Texture-Shadow-WallpapersByte-com-3840x2160.jpg"></BitmapImage>-->
<!--<BitmapImage UriSource="{Binding CurrentStorageFile}"></BitmapImage>-->
</Image.Source>
</Image>
</Grid>

Raymond is right!
CurrentImage = new BitmapImage();
await CurrentImage.SetSourceAsync(await image.StorageFile.OpenAsync(FileAccessMode.Read));
A goody for Raymond!

UWP Bluetooth Low Energy Application Disconnects Early

So I am designing an application for windows laptops to connect to a custom designed pressure sensor. The application pairs to the device and then receives notifications from the device every 10 ms. Then for some reason the communication stops. I know it is a problem with my application and not with the device, because when I connect to my phone, I do not have this problem.
Here is the main page where I create the devicewatcher and discover the device:
using System;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
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.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.Devices.Bluetooth;
using Windows.Devices.Enumeration;
// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409
namespace BLEInterfaceTest
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
{
private DeviceWatcher deviceWatcher;
private ObservableCollection<DeviceInformation> deviceList = new ObservableCollection<DeviceInformation>();
public MainPage()
{
this.InitializeComponent();
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
this.DataContext = deviceList;
deviceListView.ItemsSource = deviceList;
deviceWatcher = DeviceInformation.CreateWatcher(
"System.ItemNameDisplay:~~\"Button\"",
new string[] {
"System.Devices.Aep.DeviceAddress",
"System.Devices.Aep.IsConnected" },
DeviceInformationKind.AssociationEndpoint);
deviceWatcher.Added += DeviceWatcher_Added;
deviceWatcher.Removed += DeviceWatcher_Removed;
deviceWatcher.Start();
base.OnNavigatedTo(e);
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
AppViewBackButtonVisibility.Collapsed;
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
deviceWatcher.Stop();
base.OnNavigatedFrom(e);
}
private async void DeviceWatcher_Removed(DeviceWatcher sender, DeviceInformationUpdate args)
{
var toRemove = (from a in deviceList where a.Id == args.Id select a).FirstOrDefault();
if (toRemove != null)
{
await this.Dispatcher.RunAsync(
Windows.UI.Core.CoreDispatcherPriority.Normal,
() => { deviceList.Remove(toRemove); });
}
}
private async void DeviceWatcher_Added(DeviceWatcher sender, DeviceInformation args)
{
await this.Dispatcher.RunAsync(
Windows.UI.Core.CoreDispatcherPriority.Normal,
() => { deviceList.Add(args); });
}
private void deviceListView_ItemClick(object sender, ItemClickEventArgs e)
{
this.Frame.Navigate(typeof(DevicePage), e.ClickedItem);
}
}
}'
This next code is the page where the pressure sensor is connected to and where data is read from the device.
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
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.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.UI.Popups;
using Windows.Devices.Bluetooth.GenericAttributeProfile;
using Windows.Devices.Bluetooth;
using Windows.Devices.Enumeration;
using Windows.Storage.Pickers;
using Windows.Storage;
using Windows.Storage.Streams;
using System.Threading.Tasks;
using Windows.ApplicationModel.Background;
// The Blank Page item template is documented at https://go.microsoft.com/fwlink/?LinkId=234238
namespace BLEInterfaceTest
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class DevicePage : Page
{
private DeviceInformation device { get; set; }
private PressureSensor pSensor { get; set; }
public static DateTime startTime { get; set; }
public ObservableCollection<DataPoint> PressureData = new ObservableCollection<DataPoint>();
public static ObservableCollection<DataPoint> inbetween;
private static TextBox txtP;
private BluetoothLEDevice leDevice;
private DispatcherTimer timer = new DispatcherTimer();
private int packetNum = 0;
public DevicePage()
{
this.InitializeComponent();
SystemNavigationManager.GetForCurrentView().BackRequested += DevicePage_BackRequested;
txtP = txtValue1;
inbetween = PressureData;
}
public static void ChangeText(string text)
{
txtP.Text = text;
}
private async void InitializePressureSensor(GattDeviceService service)
{
pSensor = new PressureSensor(service, SensorUUIDs.PressureSensorUuid);
await pSensor.EnableNotifications();
btnStart.IsEnabled = true;
}
private async void StartRecievingData()
{
try
{
leDevice = await BluetoothLEDevice.FromIdAsync(device.Id);
string selector = "(System.DeviceInterface.Bluetooth.DeviceAddress:=\"" +
leDevice.BluetoothAddress.ToString("X") + "\")";
var services = await leDevice.GetGattServicesAsync(BluetoothCacheMode.Uncached);
foreach (var service in services.Services)
{
if (service.Uuid.ToString() == SensorUUIDs.ButtonSensorServiceUuid)
{
InitializePressureSensor(service);
}
}
timer.Interval = new TimeSpan(0, 0, 0, 0, 1);
timer.Tick += Timer_Tick1;
startTime = DateTime.Now;
timer.Start();
}
catch (Exception ex)
{
var messageDialog = new MessageDialog("An error has occured Please try again. \n" + ex.Message, "Error!");
}
}
public async void UpdateAllData()
{
while (pSensor != null && pSensor.MorePacketsAvailable)
{
int[] values = await pSensor.GetPressure();
int packetNumber = values[0];
if (packetNumber > packetNum)
{
packetNum = packetNumber;
txtValue1.Text = Convert.ToString(values[1]);
txtValue2.Text = Convert.ToString(values[5]);
for (int i = 1; i < 5; i++)
{
PressureData.Add(new DataPoint(DateTime.Now - startTime, packetNumber, ((i-1)*2.5 + 10*packetNumber), values[i], values[i + 4]));
}
}
}
}
private void Timer_Tick1(object sender, object e)
{
UpdateAllData();
}
private async void PairToDevice()
{
if (device.Pairing.CanPair)
{
var customPairing = device.Pairing.Custom;
customPairing.PairingRequested += CustomPairing_PairingRequested;
var result = await customPairing.PairAsync(DevicePairingKinds.ConfirmOnly);
customPairing.PairingRequested -= CustomPairing_PairingRequested;
if ((result.Status == DevicePairingResultStatus.Paired) || (result.Status == DevicePairingResultStatus.AlreadyPaired))
{
/*while (device.Pairing.IsPaired == false)
{
device = await DeviceInformation.CreateFromIdAsync(device.Id);
}*/
StartRecievingData();
}
}
else if (device.Pairing.IsPaired)
{
StartRecievingData();
}
}
private void CustomPairing_PairingRequested(DeviceInformationCustomPairing sender, DevicePairingRequestedEventArgs args)
{
args.Accept();
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
btnSave.Content = "Save";
btnStop.IsEnabled = false;
btnStart.IsEnabled = false;
this.DataContext = PressureData;
device = (DeviceInformation)e.Parameter;
PairToDevice();
//StartRecievingData();
base.OnNavigatedTo(e);
Frame rootFrame = Window.Current.Content as Frame;
if (rootFrame.CanGoBack)
{
SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
AppViewBackButtonVisibility.Visible;
}
}
private void DevicePage_BackRequested(object sender, BackRequestedEventArgs eventArgs)
{
Frame rootFrame = Window.Current.Content as Frame;
if (rootFrame == null)
{
return;
}
// Navigate back if possible, and if the event has already been handled
if (rootFrame.CanGoBack && eventArgs.Handled ==false)
{
eventArgs.Handled = true;
rootFrame.GoBack();
}
}
private async void btnSave_Click(object sender, RoutedEventArgs e)
{
timer.Stop();
var picker = new FileSavePicker();
picker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
picker.FileTypeChoices.Add("CSV", new List<string>() { ".csv" });
StorageFile file = await picker.PickSaveFileAsync();
if (file != null)
{
var stream = await file.OpenAsync(FileAccessMode.ReadWrite);
using (IOutputStream outputStream = stream.GetOutputStreamAt(0))
{
using (var writer = new DataWriter(outputStream))
{
foreach (DataPoint p in PressureData)
{
string text = p.TimeStamp.ToString() + "," + p.PacketNumber.ToString() + "," + p.InternalTimestamp.ToString() + "," + p.PressureValue1.ToString() + "," + p.PressureValue2.ToString() + "\n";
writer.WriteString(text);
}
await writer.StoreAsync();
await writer.FlushAsync();
}
}
stream.Dispose();
}
}
private async void btnStart_Click(object sender, RoutedEventArgs e)
{
if (pSensor != null)
{
btnStop.IsEnabled = true;
btnStart.IsEnabled = false;
startTime = DateTime.Now;
if (pSensor != null)
{
await pSensor.BeginCollecting();
}
}
}
private async void btnStop_Click(object sender, RoutedEventArgs e)
{
btnStart.IsEnabled = true;
btnStop.IsEnabled = false;
if (pSensor != null)
{
await pSensor.StopCollecting();
}
}
}
}
Here is where I define my SensorBase and PressureSensor class that handles the device connection:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.Devices.Bluetooth;
using Windows.Devices.Bluetooth.GenericAttributeProfile;
using Windows.Storage.Streams;
using Windows.Devices.Enumeration;
namespace BLEInterfaceTest
{
public static class SensorUUIDs
{
private static readonly string _packetUuid = "0000a043-0000-1000-8000-00805f9b34fb";
private static readonly string _buttonSensorServiceUuid = "0000a042-0000-1000-8000-00805f9b34fb";
private static readonly string _sensorStateUuid = "0000a044-0000-1000-8000-00805f9b34fb";
public static string PressureSensorUuid
{
get { return _packetUuid; }
}
public static string ButtonSensorServiceUuid
{
get { return _buttonSensorServiceUuid; }
}
public static string SensorStateUuid
{
get { return _sensorStateUuid; }
}
}
public class SensorBase : IDisposable
{
protected GattDeviceService deviceService;
protected string sensorDataUuid;
protected Queue<byte[]> fifoBuffer;
protected bool isNotificationSupported = false;
public bool newData = false;
private GattCharacteristic dataCharacteristic;
public SensorBase(GattDeviceService dataService, string sensorDataUuid)
{
this.deviceService = dataService;
this.sensorDataUuid = sensorDataUuid;
fifoBuffer = new Queue<byte[]>(20);
}
public bool MorePacketsAvailable
{
get
{
if (fifoBuffer.Count > 0)
{
return true;
}
else
{
return false;
}
}
}
public virtual async Task EnableNotifications()
{
GattCharacteristicsResult result = await deviceService.GetCharacteristicsAsync();
foreach (var test in result.Characteristics)
{
string t = test.Uuid.ToString();
}
isNotificationSupported = true;
dataCharacteristic = (await deviceService.GetCharacteristicsForUuidAsync(
new Guid(sensorDataUuid))).Characteristics[0];
dataCharacteristic.ValueChanged += dataCharacteristic_ValueChanged;
GattCommunicationStatus status = await dataCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(
GattClientCharacteristicConfigurationDescriptorValue.Notify);
var currentDescriptorValue = await dataCharacteristic.ReadClientCharacteristicConfigurationDescriptorAsync();
if (currentDescriptorValue.Status != GattCommunicationStatus.Success
|| currentDescriptorValue.ClientCharacteristicConfigurationDescriptor != GattClientCharacteristicConfigurationDescriptorValue.Notify)
{
GattCommunicationStatus status2 = await dataCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(
GattClientCharacteristicConfigurationDescriptorValue.Notify);
}
}
public virtual async Task DisableNotifications()
{
newData = false;
isNotificationSupported = false;
dataCharacteristic = (await deviceService.GetCharacteristicsForUuidAsync(
new Guid(sensorDataUuid))).Characteristics[0];
dataCharacteristic.ValueChanged -= dataCharacteristic_ValueChanged;
GattCommunicationStatus status = await dataCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.None);
}
protected async Task<byte[]> ReadValue()
{
if (!isNotificationSupported)
{
if (dataCharacteristic == null)
{
dataCharacteristic = (await deviceService.GetCharacteristicsForUuidAsync(
new Guid(sensorDataUuid))).Characteristics[0];
}
GattReadResult readResult = await dataCharacteristic.ReadValueAsync();
byte[] data = new byte[readResult.Value.Length];
DataReader.FromBuffer(readResult.Value).ReadBytes(data);
fifoBuffer.Enqueue(data);
}
return fifoBuffer.Dequeue();
}
protected async Task WriteByteArray(string characteristicUuid, byte[] value)
{
GattCharacteristic writeCharacteristic = (await deviceService.GetCharacteristicsForUuidAsync(
new Guid(characteristicUuid))).Characteristics[0];
var writer = new DataWriter();
writer.WriteBytes(value);
var res = await writeCharacteristic.WriteValueAsync(writer.DetachBuffer(), GattWriteOption.WriteWithoutResponse);
}
private void dataCharacteristic_ValueChanged(GattCharacteristic sender, GattValueChangedEventArgs args)
{
byte[] data = new byte[args.CharacteristicValue.Length];
DataReader.FromBuffer(args.CharacteristicValue).ReadBytes(data);
fifoBuffer.Enqueue(data);
newData = true;
}
public async void Dispose()
{
await DisableNotifications();
}
}
public class PressureSensor: SensorBase
{
public PressureSensor(GattDeviceService dataService, string sensorDataUuid)
: base(dataService, sensorDataUuid)
{
}
public async Task BeginCollecting()
{
await WriteByteArray(SensorUUIDs.SensorStateUuid, new byte[] { 0x01 });
}
public async Task<int[]> GetPressure()
{
byte[] data = await ReadValue();
if (data != null)
{
int[] values = new int[9];
values[0] = (int)BitConverter.ToInt32(data, 0);
for (int i = 1; i < values.Length; i++)
{
values[i] = (int)BitConverter.ToInt16(data, 2 * i + 2);
}
return values;
}
else
{
return new int[] { 0 };
}
}
public async Task StopCollecting()
{
await WriteByteArray(SensorUUIDs.SensorStateUuid, new byte[] { 0x00 });
}
}
}
Here is the DataPoint Class that I use to organize the data received from the pressure sensor:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace BLEInterfaceTest
{
public class DataPoint : INotifyPropertyChanged
{
private TimeSpan _timestamp;
private int _packetNumber;
private double _internalTimestamp;
private int _pressure1;
private int _pressure2;
public event PropertyChangedEventHandler PropertyChanged;
public TimeSpan TimeStamp
{
get { return _timestamp; }
set
{
_timestamp = value;
this.NotifyPropertyChanged();
}
}
public int PacketNumber
{
get { return _packetNumber; }
set
{
_packetNumber = value;
this.NotifyPropertyChanged();
}
}
public double InternalTimestamp
{
get { return _internalTimestamp; }
set
{
_internalTimestamp = value;
this.NotifyPropertyChanged();
}
}
public int PressureValue1
{
get { return _pressure1; }
set
{
_pressure1 = value;
this.NotifyPropertyChanged();
}
}
public int PressureValue2
{
get { return _pressure2; }
set
{
_pressure2 = value;
this.NotifyPropertyChanged();
}
}
public DataPoint(TimeSpan time,int packetNumber, double internalTimestamp, int pressure1, int pressure2)
{
_timestamp = time;
_packetNumber = packetNumber;
_internalTimestamp = internalTimestamp;
_pressure1 = pressure1;
_pressure2 = pressure2;
}
private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
if (!string.IsNullOrEmpty(propertyName))
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
I have researched this extensively, and all I could find was help on how to initiate a disconnection. I have the opposite problem. One page I found stated that the problem might be caused by the device not properly storing the bonding state, but I have checked that and I did initialize the device to save the bonding state.
Interestingly if I do not pair the device to the computer before trying to read information from it then I do not have the problem. The connection never randomly stops. But when I do this, the computer does not receive every packet of data sent from the sensor device. It will receive one or two packets and then skip five or six packets. If I pair the device then I will receive every packet but the connection will randomly cut off.
So my question is two fold, I guess. How do I stop the connection from cutting off when the device is paired? Or alternatively, is there a way to allow the application to receive every packet of data when it is not paired?
UPDATE
I realized I should include more information on my sensor peripheral in case the error is in that code. I am currently designing a rapid prototyping of this sensor before I move on to designing the embedded version. To do this, I am using the BLE Nano 1 from RedBearLabs as a user friendly prototype. I am programing this device with the online MBED compiler. I have included the nRF51822 and BLE_API libraries to handle the bluetooth low energy communication.
UPDATE 2
So after more research into what is causing the problem, I have found that the disconnection occurs when a connection interval and a generation 2 garbage collection occur at the same time. In UWP the garbage collector can pause the UI Thread for generation 2 collections. (see here)
My thought is that if the thread is paused at the beginning of a connection interval, then the central is not able to initiate the connection with the peripheral and the peripheral therefore thinks the client is no longer listening (see more about how BLE connections work).
I discovered this by finding out exactly what is necessary to get the connection back once it has randomly stopped. I started with the entire connection process and reduced it down to this:
public async Task ReconnectDevice()
{
GattCommunicationStatus status = await dataCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(
GattClientCharacteristicConfigurationDescriptorValue.Notify);
await WriteByteArray(SensorUUIDs.SensorStateUuid, new byte[] { 0x01 });
}
Because my BluetoothLEDevice, GattService, and GattCharacteristic objects are not disposed, all I need to do is resubscribe to notifications and write a 1 to the device so that it begins collecting data again.
I have reduced my memory allocations in my application significantly since discovering this, and the time for a gen2 collection has decreased to an average of 5 ms. Also, the amount of time before the connection disconnects has increased to around 4-5 sec.
UWP has a GattCharacteristicNotificationTrigger for receiving notifications in a BackgroundTask, but I have never had much success at incorporating background tasks in UWP.
I think I will try next to incorporate the windows.devices into a WPF application where I think I will have a better chance at getting it working.

So, after a while of trying different ideas I have finally stumbled across a solution to my problem. I had to make 2 changes:
Used the unpaired connection instead of the paired connection. This solved the problem of the connection dropping suddenly.
Increased the connection interval to 40 ms. For some reason when I did this, I received all of the data and no longer had any problems. Anything below 40 ms causes information to be lost when communicating to a Windows device (I had to make this change on the C code running on my sensors.)
I have used the devices for about 2 months now after making this change and have had no problems at all.

I seems to me that these problems are related to the BluetoothCacheMode Enum.
This indicates whether certain Bluetooth API methods should operate on values cached in the system or
retrieve those values from the Bluetooth device.
Using BluetoothCacheMode.Uncached attribute allows the service to update the attributes when needed.
If the device is paired then the BluetoothCacheMode is not needed(I think BluetoothCacheMode.Cached is default).
In your code the line:
var services = await leDevice.GetGattServicesAsync(BluetoothCacheMode.Uncached);
Can be the cause of the connection lost if paired.
GetGattServicesAsync(), GetCharacteristicsAsync() and ReadValueAsync()
must have the attribute BluetoothCacheMode.Uncached when not paired, when paired default or BluetoothCacheMode.Cached.
See https://msdn.microsoft.com/en-us/library/windows/apps/dn263758.aspx.

nullreferenceexception was unhandled NAudio MP3 streaming

I am using Naudios Demo app to demostrait a litle bit. I found out that when i play some mp3 file, in the end om the sound/mp3 i get a
error nullreferenceexception was unhandled
nullreferenceexception object reference not set to an instance of an
object
in the file Mp3FrameDecompressor.cs
using System;
using System.Collections.Generic;
using System.Text;
using NAudio.Wave;
using NAudio.Wave.Compression;
using System.Diagnostics;
namespace NAudio.Wave
{
/// <summary>
/// MP3 Frame Decompressor using ACM
/// </summary>
public class AcmMp3FrameDecompressor : IDisposable, IMp3FrameDecompressor
{
private AcmStream conversionStream;
private WaveFormat pcmFormat;
/// <summary>
/// Creates a new ACM frame decompressor
/// </summary>
/// <param name="sourceFormat">The MP3 source format</param>
public AcmMp3FrameDecompressor(WaveFormat sourceFormat)
{
this.pcmFormat = AcmStream.SuggestPcmFormat(sourceFormat);
conversionStream = new AcmStream(sourceFormat, pcmFormat);
}
/// <summary>
/// Output format (PCM)
/// </summary>
public WaveFormat OutputFormat { get { return pcmFormat; } }
/// <summary>
/// Decompresses a frame
/// </summary>
/// <param name="frame">The MP3 frame</param>
/// <param name="dest">destination buffer</param>
/// <param name="destOffset">Offset within destination buffer</param>
/// <returns>Bytes written into destination buffer</returns>
public int DecompressFrame(Mp3Frame frame, byte[] dest, int destOffset)
{
Array.Copy(frame.RawData, conversionStream.SourceBuffer, frame.FrameLength);
int sourceBytesConverted = 0;
int converted = conversionStream.Convert(frame.FrameLength, out sourceBytesConverted);
if (sourceBytesConverted != frame.FrameLength)
{
throw new InvalidOperationException(String.Format("Couldn't convert the whole MP3 frame (converted {0}/{1})",
sourceBytesConverted, frame.FrameLength));
}
Array.Copy(conversionStream.DestBuffer, 0, dest, destOffset, converted);
return converted;
}
/// <summary>
/// Disposes of this MP3 frame decompressor
/// </summary>
public void Dispose()
{
if (this.conversionStream != null)
{
this.conversionStream.Dispose();
this.conversionStream = null;
}
}
}
}
This is the Form i use
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using NAudio.Wave;
using System.Net;
using System.Threading;
using System.Net.Sockets;
using System.IO;
using System.Diagnostics;
using System.ComponentModel.Composition;
namespace NAudioDemo
{
public partial class MP3StreamingPanel : Form
{
public MP3StreamingPanel()
{
InitializeComponent();
this.volumeSlider1.VolumeChanged += new EventHandler(volumeSlider1_VolumeChanged);
this.Disposed += this.MP3StreamingPanel_Disposing;
}
enum StreamingPlaybackState
{
Stopped,
Playing,
Buffering,
Paused
}
void volumeSlider1_VolumeChanged(object sender, EventArgs e)
{
if (this.volumeProvider != null)
{
this.volumeProvider.Volume = this.volumeSlider1.Volume;
}
}
private BufferedWaveProvider bufferedWaveProvider;
private IWavePlayer waveOut;
private volatile StreamingPlaybackState playbackState;
private volatile bool fullyDownloaded;
private HttpWebRequest webRequest;
private VolumeWaveProvider16 volumeProvider;
delegate void ShowErrorDelegate(string message);
private void ShowError(string message)
{
if (this.InvokeRequired)
{
this.BeginInvoke(new ShowErrorDelegate(ShowError), message);
}
else
{
MessageBox.Show(message);
}
}
private void StreamMP3(object state)
{
this.fullyDownloaded = false;
string url = (string)state;
webRequest = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse resp = null;
try
{
resp = (HttpWebResponse)webRequest.GetResponse();
}
catch(WebException e)
{
if (e.Status != WebExceptionStatus.RequestCanceled)
{
ShowError(e.Message);
}
return;
}
byte[] buffer = new byte[16384 * 4]; // needs to be big enough to hold a decompressed frame
IMp3FrameDecompressor decompressor = null;
try
{
using (var responseStream = resp.GetResponseStream())
{
var readFullyStream = new ReadFullyStream(responseStream);
do
{
if (bufferedWaveProvider != null && bufferedWaveProvider.BufferLength - bufferedWaveProvider.BufferedBytes < bufferedWaveProvider.WaveFormat.AverageBytesPerSecond / 4)
{
Debug.WriteLine("Buffer getting full, taking a break");
Thread.Sleep(500);
}
else
{
Mp3Frame frame = null;
try
{
frame = Mp3Frame.LoadFromStream(readFullyStream);
}
catch (EndOfStreamException)
{
this.fullyDownloaded = true;
// reached the end of the MP3 file / stream
break;
}
catch (WebException)
{
// probably we have aborted download from the GUI thread
break;
}
if (decompressor == null)
{
// don't think these details matter too much - just help ACM select the right codec
// however, the buffered provider doesn't know what sample rate it is working at
// until we have a frame
WaveFormat waveFormat = new Mp3WaveFormat(frame.SampleRate, frame.ChannelMode == ChannelMode.Mono ? 1 : 2, frame.FrameLength, frame.BitRate);
decompressor = new AcmMp3FrameDecompressor(waveFormat);
this.bufferedWaveProvider = new BufferedWaveProvider(decompressor.OutputFormat);
this.bufferedWaveProvider.BufferDuration = TimeSpan.FromSeconds(20); // allow us to get well ahead of ourselves
//this.bufferedWaveProvider.BufferedDuration = 250;
}
int decompressed = decompressor.DecompressFrame(frame, buffer, 0);
//Debug.WriteLine(String.Format("Decompressed a frame {0}", decompressed));
bufferedWaveProvider.AddSamples(buffer, 0, decompressed);
}
} while (playbackState != StreamingPlaybackState.Stopped);
Debug.WriteLine("Exiting");
// was doing this in a finally block, but for some reason
// we are hanging on response stream .Dispose so never get there
decompressor.Dispose();
}
}
finally
{
if (decompressor != null)
{
decompressor.Dispose();
}
}
}
private void buttonPlay_Click(object sender, EventArgs e)
{
if (playbackState == StreamingPlaybackState.Stopped)
{
playbackState = StreamingPlaybackState.Buffering;
this.bufferedWaveProvider = null;
ThreadPool.QueueUserWorkItem(new WaitCallback(StreamMP3), textBoxStreamingUrl.Text);
timer1.Enabled = true;
}
else if (playbackState == StreamingPlaybackState.Paused)
{
playbackState = StreamingPlaybackState.Buffering;
}
}
private void StopPlayback()
{
if (playbackState != StreamingPlaybackState.Stopped)
{
if (!fullyDownloaded)
{
webRequest.Abort();
}
this.playbackState = StreamingPlaybackState.Stopped;
if (waveOut != null)
{
waveOut.Stop();
waveOut.Dispose();
waveOut = null;
}
timer1.Enabled = false;
// n.b. streaming thread may not yet have exited
Thread.Sleep(500);
ShowBufferState(0);
}
}
private void ShowBufferState(double totalSeconds)
{
}
private void timer1_Tick(object sender, EventArgs e)
{
if (playbackState != StreamingPlaybackState.Stopped)
{
if (this.waveOut == null && this.bufferedWaveProvider != null)
{
Debug.WriteLine("Creating WaveOut Device");
this.waveOut = CreateWaveOut();
waveOut.PlaybackStopped += waveOut_PlaybackStopped;
this.volumeProvider = new VolumeWaveProvider16(bufferedWaveProvider);
this.volumeProvider.Volume = this.volumeSlider1.Volume;
waveOut.Init(volumeProvider);
progressBarBuffer.Maximum = (int)bufferedWaveProvider.BufferDuration.TotalMilliseconds;
}
else if (bufferedWaveProvider != null)
{
var bufferedSeconds = bufferedWaveProvider.BufferedDuration.TotalSeconds;
ShowBufferState(bufferedSeconds);
// make it stutter less if we buffer up a decent amount before playing
if (bufferedSeconds < 0.5 && this.playbackState == StreamingPlaybackState.Playing && !this.fullyDownloaded)
{
this.playbackState = StreamingPlaybackState.Buffering;
waveOut.Pause();
Debug.WriteLine(String.Format("Paused to buffer, waveOut.PlaybackState={0}", waveOut.PlaybackState));
}
else if (bufferedSeconds > 1 && this.playbackState == StreamingPlaybackState.Buffering)
{
waveOut.Play();
Debug.WriteLine(String.Format("Started playing, waveOut.PlaybackState={0}", waveOut.PlaybackState));
this.playbackState = StreamingPlaybackState.Playing;
}
else if (this.fullyDownloaded && bufferedSeconds == 0)
{
Debug.WriteLine("Reached end of stream");
StopPlayback();
}
}
}
}
private IWavePlayer CreateWaveOut()
{
return new WaveOut();
//return new DirectSoundOut();
}
private void MP3StreamingPanel_Disposing(object sender, EventArgs e)
{
StopPlayback();
}
private void buttonPause_Click(object sender, EventArgs e)
{
if (playbackState == StreamingPlaybackState.Playing || playbackState == StreamingPlaybackState.Buffering)
{
waveOut.Pause();
Debug.WriteLine(String.Format("User requested Pause, waveOut.PlaybackState={0}", waveOut.PlaybackState));
playbackState = StreamingPlaybackState.Paused;
}
}
private void buttonStop_Click(object sender, EventArgs e)
{
StopPlayback();
}
private void waveOut_PlaybackStopped(object sender, StoppedEventArgs e)
{
Debug.WriteLine("Playback Stopped");
if (e.Exception != null)
{
MessageBox.Show(String.Format("Playback Error {0}", e.Exception.Message));
}
}
}
[Export(typeof(INAudioDemoPlugin))]
public class MP3StreamingPanelPlugin : INAudioDemoPlugin
{
public string Name
{
get { return "MP3 Streaming"; }
}
public Control CreatePanel()
{
return new MP3StreamingPanel();
}
}
}
i get the error on this line
Array.Copy(frame.RawData, conversionStream.SourceBuffer, frame.FrameLength);

NAudio Volume Changing

class Sound
{
private NAudio.Wave.BlockAlignReductionStream stream = null;
private NAudio.Wave.DirectSoundOut output = null;
private string fileName;
public Sound(string fileName)
{
this.fileName = fileName;
}
public void PlaySound()
{
if(fileName.EndsWith(".mp3"))
{
NAudio.Wave.WaveStream pcm = NAudio.Wave.WaveFormatConversionStream.CreatePcmStream(new NAudio.Wave.Mp3FileReader(fileName));
stream = new NAudio.Wave.BlockAlignReductionStream(pcm);
}
else if (fileName.EndsWith(".wav"))
{
NAudio.Wave.WaveStream pcm = new NAudio.Wave.WaveChannel32(new NAudio.Wave.WaveFileReader(fileName));
stream = new NAudio.Wave.BlockAlignReductionStream(pcm);
}
else throw new InvalidOperationException("Not a correct audio file type.");
output = new NAudio.Wave.DirectSoundOut();
output.Init(stream);
output.Play();
output.Volume = 0.5f;
}
public void Volume(float vol)
{
}
public void PausePlay()
{
if (output != null)
{
if (output.PlaybackState == NAudio.Wave.PlaybackState.Playing) output.Pause();
else if (output.PlaybackState == NAudio.Wave.PlaybackState.Paused) output.Play();
}
}
public void Pause()
{
if (output != null)
{
if (output.PlaybackState == NAudio.Wave.PlaybackState.Playing) output.Pause();
}
}
public void Play()
{
if (output != null)
{
if (output.PlaybackState == NAudio.Wave.PlaybackState.Paused) output.Play();
}
}
public void DisposeWave()
{
if (output != null)
{
if (output.PlaybackState == NAudio.Wave.PlaybackState.Playing) output.Stop();
output.Dispose();
output = null;
}
if (stream != null)
{
stream.Dispose();
stream = null;
}
}
public bool Over()
{
if (stream.Position == stream.Length)
return true;
return false;
}
public void Loop()
{
if (Over())
{
stream.Position = 0;
output.Play();
}
}
I really don't know what's the problem here, I'd be glad for a help, I'm trying to change the volume of the output audio.
When I compile this code I'm getting an error in the output.volume = 0.5. The error is:
Setting volume not supported on DirectSoundOut, adjust the volume on your WaveProvider instead.

It means, use the Volume property on WaveChannel32 instead. Also, unless you are using an old version of NAudio, the BlockAlignReductionStream and the WaveFormatConversion stream are unneccessary, since MP3FileReader emits PCM.

How to use a thread in a playback function

I want to playback a sound file in two or three external sound cards at the same time and I think that using threads is the solution but I really didn't know how to use it in the playback code.
This is the event makes on button play:
public partial class PlaybackForm : Form
{
IWavePlayer waveOut;
string fileName = null;
WaveStream mainOutputStream;
WaveChannel32 volumeStream;
int _deviceNum;
int _deviceNum1;
Thread t1;
Thread t2;
public PlaybackForm(int deviceNum,int deviceNum1)
{
InitializeComponent();
_deviceNum = deviceNum;
_deviceNum1 = deviceNum1;
}
private void buttonPlay_Click(object sender, EventArgs e)
{
if (waveOut != null)
{
if (waveOut.PlaybackState == PlaybackState.Playing)
{
return;
}
else if (waveOut.PlaybackState == PlaybackState.Paused)
{
waveOut.Play();
return;
}
}
// we are in a stopped state
// TODO: only re-initialise if necessary
if (String.IsNullOrEmpty(fileName))
{
toolStripButtonOpenFile_Click(sender, e);
}
if (String.IsNullOrEmpty(fileName))
{
return;
}
try
{
CreateWaveOut();
}
catch (Exception driverCreateException)
{
MessageBox.Show(String.Format("{0}", driverCreateException.Message));
return;
}
mainOutputStream = CreateInputStream(fileName);
trackBarPosition.Maximum = (int)mainOutputStream.TotalTime.TotalSeconds;
labelTotalTime.Text = String.Format("{0:00}:{1:00}", (int)mainOutputStream.TotalTime.TotalMinutes,
mainOutputStream.TotalTime.Seconds);
trackBarPosition.TickFrequency = trackBarPosition.Maximum / 30;
try
{
waveOut.Init(mainOutputStream);
}
catch (Exception initException)
{
MessageBox.Show(String.Format("{0}", initException.Message), "Error Initializing Output");
return;
}
// not doing Volume on IWavePlayer any more
volumeStream.Volume = volumeSlider1.Volume;
waveOut.Play();
}
And this is how to create the waveout:
private void CreateWaveOut()
{
CloseWaveOut();
int latency = (int)comboBoxLatency.SelectedItem;
//if (radioButtonWaveOut.Checked)
{
//WaveCallbackInfo callbackInfo = checkBoxWaveOutWindow.Checked ?
WaveCallbackInfo callbackInfo = WaveCallbackInfo.FunctionCallback();
// WaveCallbackInfo callbackInfo = WaveCallbackInfo.FunctionCallback();
// WaveCallbackInfo.NewWindow(): WaveCallbackInfo.FunctionCallback();
WaveOut outputDevice = new WaveOut(callbackInfo);
outputDevice.DesiredLatency = latency;
outputDevice.DeviceNumber = _deviceNum;
waveOut = outputDevice;
}
}
I declared two deviceNum but until now I can playsound only in one device,that's why I want to use thread.
Can you help me please
Thank you in advance

Do something like that:
using System.Threading;
...
private void buttonPlay_Click(object sender, EventArgs e)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(this.PlaySound), 1);
ThreadPool.QueueUserWorkItem(new WaitCallback(this.PlaySound), 2);
}
private void PlaySound(object obj)
{
int deviceNumber = (int)obj;
// Do the stuff you used to do in buttonPlay_Click
WaveOut myWaveOut = CreateWaveOut(deviceNumber);
...
}
private WaveOut CreateWaveOut(int deviceNumber)
{
...
WaveOut outputDevice = new WaveOut(callbackInfo);
outputDevice.DesiredLatency = latency;
outputDevice.DeviceNumber = _deviceNum;
return outputDevice;
}