播放 YouTube 的 C# LibVLCSharp 问题

Question

我正在尝试在 WPF 应用程序中的多个实例中使用 LibVLC 播放 YouTube。这可能在 75% 的时间里工作正常，但流会卡住一两秒钟，而在另外 25% 的时间里会被像素化。这似乎是随机的。

这是我的代码:

public async void PlayUri(string path, bool isMuted, bool repeat)
{
    await Dispatcher.InvokeAsync(new Action(async () =>
    {
        Core.Initialize();

        using (LibVLC libVLC = new LibVLC(MediaOptions(repeat)))
        {
            using (var media = new Media(libVLC, path, FromType.FromLocation))
            {
                await media.Parse(MediaParseOptions.ParseNetwork);
                vlcPlayer = new MediaPlayer(media.SubItems.FirstOrDefault());
                if (!repeat)
                    vlcPlayer.EndReached += (sender, args) => ThreadPool.QueueUserWorkItem(_ => waitHandle.Set());
                VideoView.MediaPlayer = vlcPlayer;
                VideoView.MediaPlayer.Play();
            }

            // Set the sound and audio output device            
            SetAudioToDirectsound(isMuted);
        }
    }));            
}

MediaOptions 只是传递一个字符串[]

mediaOptions = new[]
{
    "--input-repeat=5",
    "--sout-mux-caching=12000"
};

并且(为了完整性)SetAudioToDirectSount(bool)

var directsound = VideoView.MediaPlayer.SetAudioOutput("directsound");
IsMuted = isMuted;

这个“--sout-mux-caching=12000”选项应该缓存接下来的 12 秒视频。
这是正确的吗，我还需要其他选择吗？我查看了所有 cmd 行选项，似乎找不到任何明显的东西。

阅读最佳实践here , 它提到
“VL​​C 核心开发人员建议在应用程序的生命周期中只创建一个 LibVLC 类型的实例。您可以根据需要从单个 LibVLC 对象创建任意数量的 MediaPlayer 对象。”

在我的例子中，它嵌套在一个 using 语句中，所以我似乎没有遵循最佳实践。所以我应该声明:

Core.Initialize();
public LibVLC libVLC {get; set; } = new LibVLC();

只有一次，并且只在卸载时处理 MediaPlayer？


最小测试解决方案

名为 VLCStream 的新 WPF 项目

NuGet 安装:

• VideoLAN.LibVLC.Windows
  
• LibVLCSharp.WPF
  
• LibVLCSharp
  
  

主窗口.xaml

<Window x:Class="VLCStream.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:vlc="clr-namespace:LibVLCSharp.WPF;assembly=LibVLCSharp.WPF"
        xmlns:local="clr-namespace:VLCStream"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800"
        Loaded="Window_Loaded">
    
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="40" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <Button Content="Play" Click="Button_Click" />

        <vlc:VideoView x:Name="VideoView" Grid.Row="1" />
    </Grid>
</Window>

MainWindow.xaml.cs

using LibVLCSharp.Shared;
using LibVLCSharp.WPF;
using System;
using System.Linq;
using System.Windows;

namespace VLCStream
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Dispatcher.InvokeAsync(new Action(async () =>
            {
                using (LibVLC libVLC = new LibVLC("--sout-mux-caching=12000"))
                {
                    using (var media = new Media(libVLC, "https://youtu.be/pW-iVG0_D34", FromType.FromLocation))
                    {
                        await media.Parse(MediaParseOptions.ParseNetwork);
                        MediaPlayer vlcPlayer = new MediaPlayer(media.SubItems.FirstOrDefault());
                        VideoView.MediaPlayer = vlcPlayer;
                        VideoView.MediaPlayer.Play();
                    }
                }
            }));
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            Core.Initialize();
        }
    }
}

问题似乎是随机的，需要不止 1 次运行。

Answer 1

对您的代码的一般反馈。

• 在使用媒体播放器的过程中一直对其进行跟踪，并在用完后将其丢弃。
• 不要在使用 LibVLC 时丢弃它。
• 将每个媒体播放器与一个 View 集成，现在您只是在没有绘图目标的媒体播放器上调用播放。 LibVLC 将创建随机窗口以供绘制。可能不是您想要的。

现在，在打开日志的情况下在 VLC 桌面应用程序中播放您的流将提供一些见解:

main error: ES_OUT_SET_(GROUP_)PCR is called too late (pts_delay increased to 2926 ms)
main debug: Received first picture
main error: Timestamp conversion failed for 9480001: no reference clock
main error: Could not convert timestamp 0 for FFmpeg
main debug: Buffering 0%
main debug: Buffering 8%
main debug: Buffering 17%
main debug: Buffering 25%
main debug: Buffering 34%
main debug: Buffering 42%
main debug: Buffering 51%
main debug: Buffering 59%
main debug: Buffering 68%
main debug: Buffering 76%
main debug: Buffering 85%
main debug: Buffering 93%
main debug: Stream buffering done (3000 ms in 7056 ms)
main debug: Decoder wait done in 0 ms
main debug: inserting 307 zeroes
mmdevice debug: state changed: 1
main warning: buffer too late (-217851 us): dropped
main warning: buffer too late (-194631 us): dropped
main error: ES_OUT_SET_(GROUP_)PCR is called too late (pts_delay increased to 3774 ms)
main debug: ES_OUT_RESET_PCR called
main warning: buffer too late (-171411 us): dropped
main debug: Received first picture
main error: Timestamp conversion failed for 15800001: no reference clock
main error: Could not convert timestamp 0 for FFmpeg
mmdevice debug: state changed: 0

这看起来不太好。也许 YouTube 对视频编码不当？或者更可能是 LibVLC 的问题？我不确定。