MediaElement体积-速度

Question

我正在用MediaElement构建一个UWP应用程序。

我希望能够改变MediaElement的音量和播放速度，但是我的代码不能正常工作。

如果我在第一次演奏之前设定了音量和速度，但是如果我改变了。播放后的音量不会改变音量。

我的代码：

Private mElement As MediaElement

Private Async Sub MainPage_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
    mElement = New MediaElement
    AddHandler mElement.MediaEnded, AddressOf OnMediaEnded
End Sub

Async Function SayAsync(ByVal text As String) As Task
    If Synth Is Nothing Then
        Dim chosenVoice = SpeechSynthesizer.AllVoices.First(Function(v) v.DisplayName.Contains(cboVoice.SelectedItem.ToString))
        Synth = New SpeechSynthesizer() With {.Voice = chosenVoice}
    End If
    currentStream = Await Synth.SynthesizeTextToStreamAsync(text)
    mElement.Volume = SpeechVol / 100
    mElement.PlaybackRate = SpeechSpeed / 100
    mElement.SetSource(currentStream, String.Empty)
    mElement.Play()
End Function

Private Sub OnMediaEnded(ByVal sender As Object, ByVal e As RoutedEventArgs)
    currentStream?.Dispose()
    currentStream = Nothing
End Sub

Answer 1

通过在我这边的测试，当音频播放时，Volume可以被正确地改变。由于您的代码片段只是整体的一部分，下面是一个完整的演示程序，可以在我这边很好地工作：

XAML

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" x:Name="rootgrid"> 
   <Button x:Name="btnstart" Click="btnstart_Click" Content="start play"></Button>
   <Button x:Name="btnchangevolume" Click="btnchangevolume_Click" Content="change volume to 50" Margin="100"></Button>
</Grid>

代码背后

Inherits Page

Private mElement As MediaElement
Private Synth As SpeechSynthesizer
Private currentStream As SpeechSynthesisStream 

Private Async Sub MainPage_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
    mElement = New MediaElement
    rootgrid.Children.Add(mElement)
End Sub

Async Function SayAsync(ByVal text As String) As Task
    Synth = New SpeechSynthesizer
    currentStream = Await Synth.SynthesizeTextToStreamAsync(text)
    mElement.Volume = 10 / 100
    mElement.PlaybackRate = 50 / 100
    mElement.SetSource(currentStream, String.Empty)

End Function

Private Async Sub btnstart_Click(sender As Object, e As RoutedEventArgs)
    Await SayAsync("The privacy statement was declined." +
       "Go to Settings -> Privacy -> Speech, inking and typing, and ensure you" +
       "have viewed the privacy policy, and 'Get To Know You' is enabled.")
End Sub

Private Sub btnchangevolume_Click(sender As Object, e As RoutedEventArgs)
    mElement.Volume = 50 / 100
End Sub

可能的原因可能是在XAML后面创建代码之后，没有将MediaElement添加到XAML中。如果你仍然有问题，请提供一个最小的复制项目。

顺便说一句，在Windows 10中，构建1607或更高版本，我们建议您使用MediaPlayerElement代替MediaElement。