使用Delphi自动化VideoLan的VLC [英] Automating VideoLan's VLC using Delphi

问题描述

我已经从VideoLan VLC播放器的v.2.2.1
生成了一个类型库导入单元，并将所得的插件组件嵌入到一个简单的Delphi（D7和XE8）表单中。代码摘要在下面。

I've generated a type-library import unit from v.2.2.1 of VideoLan's VLC player and embedded the resulting plug-in component in a simple Delphi (D7 and XE8) form. Code extract is below.

组件的基本功能很好 - 我可以播放（本地）.MP4文件，
停止它，加快速度和下来等没有任何问题。但是，有一个基本的
函数不起作用，即音量控制。

The basic functionality of the component is fine - I can play a (local) .MP4 file, stop it, speed it up and down, etc without any problem. However, there is one basic function which is not working, namely volume control.

插件显示v。simple（与VLC作为应用程序运行）
toobar在底部有两个轨道栏，一个显示+更改播放
在视频中的位置，另一个用于控制音频音量。后者是
，最初显示为100（％）。

The plug-in displays a v. simple (compared with the one in VLC running as an app) toobar at the bottom with two track-bars, one to display + change the playing position in the video and the other for controlling audio volume. The latter is initially shown with the volume at 100 (%).

如果我尝试通过点击轨道栏来更改它，我得到一个太多未处理的
异常错误（EInvalidOp）。如果我安装了一个Application.OnException处理程序，并且
捕获异常，插件将变得无响应，我必须在IDE中重新设置
。如果我在代码中读取Volume设置，然后将
设置为刚刚读取的值，那么也会发生。

If I attempt to change it by clicking on the track bar, I get a "Too many unhandled exceptions" error (EInvalidOp). If I install an Application.OnException handler and catch the exception, the plug-in becomes unresponsive and I have to reset the app in the IDE. The same happens if I read the Volume setting in code and then just set it to the value I've just read.

在事件中，在呼叫中，Get8087CW返回相同的值，
4798，因为我在应用启动时保存。

Inside events that the plug-in calls out from, Get8087CW returns the same value, 4798, as I save when the app starts.

我的问题是：如何避免这些异常尝试通过GUI跟踪栏或代码更改
卷？我错过了一步，也许或者是有
我可以做的是将8087的值或异常处理设置为
，阻止应用锁定？ （btw，可以在代码中显示插件的工具栏，所以如果一切都失败，我可以用自己的方式替换它，但是如果可能，我宁愿让VLC一个正常工作）。

My question is: How to avoid these exceptions when attempting to change the volume via the GUI trackbar or in code? Am I missing a step, maybe, or is there something I could do in terms of setting the 8087 value or exception-handling to prevent the app locking up? (btw, it is possible to turn the display of the plug-in's toolbar in code, so I could replace it by one of my own if all else fails, but I'd rather get the VLC one working properly, if possible).

代码：

TForm1 = class(TForm)
  VLCPlugin1: TVLCPlugin;
  [...]
public
  { Public declarations }
  IPlugIn : IVlcControl;
  IPlugIn2 : IVlcControl2;
  Input : IVlcInput;
  PlayList : IVlcPlayList;
  IAudio : IVlcAudio;
  Speed : Integer;
  Volume : Integer;
  Saved8087CW : Integer;
  procedure PlayFile;
  property FileName : WideString read FFileName write SetFileName;
end;

// This routine, NoOp, is one I've used since D1 to facilitate single-stepping
// through code and checking values on the way.  It accesses the NoOpCount
// global variable because I assumed/hoped the compiler's optimiser wouldn't optimise it away.
var
  NoOpCount : Integer;
procedure NoOp;
begin
  Inc(NoOpCount);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Application.OnException := HandleException;
  Saved8087CW := Get8087CW;
end;

procedure TForm1.PlayFile;
begin
  Assert((Trim(FileName) <> '') and (FileExists(FileName)));
  if VLCPlugIn1.Playing then
    VLCPlugIn1.stop;

  IPlugIn := VlcPlugIn1.ControlInterface;

  //VLC's VLCPlugIn2 contains some extra methods compared to VLCPlugIn, so
  IPlugIn.QueryInterface(VlcPlugIn2, IPlugIn2);
  if IPlugIn2 = Nil then
    NoOp
  else
    NoOp;

  IAudio := IPlugIn2.Audio;  // this is the interface to the object which gets/sets the volume
  if IAudio = Nil then
    NoOp
  else
    NoOp;

  Input := IPlugIn2.Input;
  if Input = Nil then
    NoOp
  else
    NoOp;

  VLCPlugin1.addTarget('file:///' + FileName, null, VLCPlayListInsert, 0);

{  The following assignment to IAudio.Volume causes an EInvalidOp exception
  Volume := IAudio.Volume;
  IAudio.Volume := Volume;
}

  VlcPlugIn1.AutoLoop := True;

  IPlugIn2.playlist.play;
end;

procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  if IPlugIn.Playing then
    IPlugIn.Stop;
end;

procedure TForm1.VLCPlugin1MediaPlayerPlaying(Sender: TObject);
begin
  if Saved8087CW = Get8087CW then
    NoOp
  else
    NoOp;
end;

procedure TForm1.VLCPlugin1play(Sender: TObject);
begin
  if IAudio <> Nil then begin
    Volume := IAudio.Volume;
    // IAudio.Volume := Volume; <- provokes EInvalidOp
  end;
end;

procedure TForm1.HandleException(Sender: TObject; E: Exception);
begin
  if Saved8087CW = Get8087CW then
    NoOp
  else
    NoOp;
end;

推荐答案

尝试在启动时禁用FPU异常：

Try to disable FPU exceptions on startup:

Set8087CW($133F);

或（用于现代Delphi）

Or (for modern Delphi)

Math.SetExceptionMask(exAllArithmeticExceptions);

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