.NET Expression SDK LiveJob身份验证

我正在尝试将一个实时提要流式传输到发布点,但不断出现“访问被拒绝”错误。我可以在ExpressionEncoder应用程序中很好地做到这一点(使用有效的用户名和密码)。但是,当我尝试在我的自定义应用程序中使用相同的用户名/密码时,我会出现错误。我已尝试在没有凭据的情况下预连接,这将触发AcquireCredentials事件。

LiveJob job = new LiveJob();

LiveDevice audioDevice = (LiveDevice)cmbAudioDevices.SelectedItem;
LiveDevice videoDevice = (LiveDevice)cmbVideoDevices.SelectedItem;

LiveDeviceSource liveSource = job.AddDeviceSource(videoDevice, audioDevice);
job.ActivateSource(liveSource);

System.Runtime.InteropServices.HandleRef h = new System.Runtime.InteropServices.HandleRef(panel1, panel1.Handle);

job.DeviceSources[0].PreviewWindow = new PreviewWindow(h)
{
    Visible = true
};

System.Security.SecureString password = new System.Security.SecureString();
foreach (char letter in txtPassword.Text.ToCharArray())
    password.AppendChar(letter);

job.OutputFormat = new WindowsMediaPublishingPointOutputFormat()
{
    PublishingPoint = new Uri(txtPublishPoint.Text)
    UserName = txtUsername.Text,
    Password = password
};

job.PreConnectPublishingPoint();

有什么想法吗?