constructor Create(Name: String; Unk: IUnKnown; Form: TFormPropertyPage);
    destructor  Destroy; override;
    procedure SetPageDirty;

    { IPropertyPage }
    function SetPageSite(const pageSite: IPropertyPageSite): HResult; stdcall;
    function Activate(hwndParent: HWnd; const rc: TRect; bModal: BOOL): HResult; stdcall;
    function Deactivate: HResult; stdcall;
    function GetPageInfo(out pageInfo: TPropPageInfo): HResult; stdcall;
    function SetObjects(cObjects: Longint; pUnkList: PUnknownList): HResult; stdcall;
    function Show(nCmdShow: Integer): HResult; stdcall;
    function Move(const rect: TRect): HResult; stdcall;
    function IsPageDirty: HResult; stdcall;
    function Apply: HResult; stdcall;
    function Help(pszHelpDir: POleStr): HResult; stdcall;
    function TranslateAccelerator(msg: PMsg): HResult; stdcall;
  end;

  TOnConnect = procedure(sender: Tobject; Unknown: IUnknown) of object;

  TFormPropertyPage = class(TForm, IUnKnown, IPropertyPage)
  private
    FPropertyPage: TBCBasePropertyPage;
    procedure MyWndProc(var aMsg: TMessage);
  public
    constructor Create(AOwner: TComponent); override;
  published
    function OnConnect(Unknown: IUnknown): HRESULT; virtual;
    function OnDisconnect: HRESULT; virtual;
    function OnApplyChanges: HRESULT; virtual;
    property PropertyPage   : TBCBasePropertyPage read FPropertyPage implements IUnKnown, IPropertyPage;
  end;

  TBCBaseDispatch = class{IDispatch}
  protected
    FTI: ITypeInfo;
  public
    // IDispatch methods
    function GetTypeInfoCount(out Count: Integer): HResult; stdcall;
    function GetTypeInfo(const iid: TGUID; info: Cardinal; lcid: LCID; out tinfo): HRESULT; stdcall;
    function GetIDsOfNames(const IID: TGUID; Names: Pointer;
      NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; stdcall;
  end;

  TBCMediaControl = class(TBCUnknown, IDispatch)
  public
    FBaseDisp: TBCBaseDispatch;
    constructor Create(name: string; unk: IUnknown);
    destructor Destroy; override;

    // IDispatch methods
    function GetTypeInfoCount(out Count: Integer): HResult; stdcall;
    function GetTypeInfo(Index, LocaleID: Integer; out TypeInfo): HResult; stdcall;
    function GetIDsOfNames(const IID: TGUID; Names: Pointer;
      NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; stdcall;
    function Invoke(DispID: Integer; const IID: TGUID; LocaleID: Integer;
      Flags: Word; var Params; VarResult, ExcepInfo, ArgErr: Pointer): HResult; stdcall;
  end;

  TBCMediaEvent = class(TBCUnknown, IDisPatch{,IMediaEventEx})
  protected
    FBasedisp: TBCBaseDispatch;
  public
    constructor Create(Name: string; Unk: IUnknown);
    destructor destroy; override;
    // IDispatch methods
    function GetTypeInfoCount(out Count: Integer): HResult; stdcall;
    function GetTypeInfo(Index, LocaleID: Integer; out TypeInfo): HResult; stdcall;
    function GetIDsOfNames(const IID: TGUID; Names: Pointer;
      NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; stdcall;
    function Invoke(DispID: Integer; const IID: TGUID; LocaleID: Integer;
      Flags: Word; var Params; VarResult, ExcepInfo, ArgErr: Pointer): HResult; stdcall;
  end;

  TBCMediaPosition = class(TBCUnknown, IDispatch {IMediaPosition})
  protected
    FBaseDisp: TBCBaseDispatch;
  public
    constructor Create(Name: String; Unk: IUnknown); overload;
    constructor Create(Name: String; Unk: IUnknown; out hr: HRESULT); overload;
    destructor Destroy; override;
    // IDispatch methods
    function GetTypeInfoCount(out Count: Integer): HResult; stdcall;
    function GetTypeInfo(Index, LocaleID: Integer; out TypeInfo): HResult; stdcall;
    function GetIDsOfNames(const IID: TGUID; Names: Pointer;
      NameCount, LocaleID: Integer; DispIDs: Pointer): HResult; stdcall;
    function Invoke(DispID: Integer; const IID: TGUID; LocaleID: Integer;
      Flags: Word; var Params; VarResult, ExcepInfo, ArgErr: Pointer): HResult; stdcall;
  end;


// A utility class that handles IMediaPosition and IMediaSeeking on behalf
// of single-input pin renderers, or transform filters.
//
// Renderers will expose this from the filter; transform filters will
// expose it from the output pin and not the renderer.
//
// Create one of these, giving it your IPin* for your input pin, and delegate
// all IMediaPosition methods to it. It will query the input pin for
// IMediaPosition and respond appropriately.
//
// Call ForceRefresh if the pin connection changes.
//
// This class no longer caches the upstream IMediaPosition or IMediaSeeking
// it acquires it on each method call. This means ForceRefresh is not needed.
// The method is kept for source compatibility and to minimise the changes
// if we need to put it back later for performance reasons.

  TBCPosPassThru = class(TBCMediaPosition, IMediaSeeking)
  protected
    FPin: IPin;
    function GetPeer(out MP: IMediaPosition): HRESULT;
    function GetPeerSeeking(out MS: IMediaSeeking): HRESULT;
  public

    constructor Create(name: String; Unk: IUnknown; out hr: HRESULT; Pin: IPin);
    function ForceRefresh: HRESULT;{return S_OK;}

    // override to return an accurate current position
    function GetMediaTime(out StartTime, EndTime: int64): HRESULT; virtual;

    // IMediaSeeking methods
    function GetCapabilities(out pCapabilities: DWORD): HRESULT; stdcall;
    function CheckCapabilities(var pCapabilities: DWORD): HRESULT; stdcall;
    function IsFormatSupported(const pFormat: TGUID): HRESULT; stdcall;
    function QueryPreferredFormat(out pFormat: TGUID): HRESULT; stdcall;
    function GetTimeFormat(out pFormat: TGUID): HRESULT; stdcall;
    function IsUsingTimeFormat(const pFormat: TGUID): HRESULT; stdcall;
    function SetTimeFormat(const pFormat: TGUID): HRESULT; stdcall;
    function GetDuration(out pDuration: int64): HRESULT; stdcall;
    function GetStopPosition(out pStop: int64): HRESULT; stdcall;
    function GetCurrentPosition(out pCurrent: int64): HRESULT; stdcall;
    function ConvertTimeFormat(out pTarget: int64; pTargetFormat: PGUID;
               Source: int64; pSourceFormat: PGUID): HRESULT; stdcall;
    function SetPositions(var pCurrent: int64; dwCurrentFlags: DWORD;
               var pStop: int64; dwStopFlags: DWORD): HRESULT; stdcall;
    function GetPositions(out pCurrent, pStop: int64): HRESULT; stdcall;
    function GetAvailable(out pEarliest, pLatest: int64): HRESULT; stdcall;
    function SetRate(dRate: double): HRESULT; stdcall;
    function GetRate(out pdRate: double): HRESULT; stdcall;
    function GetPreroll(out pllPreroll: int64): HRESULT; stdcall;

    // IMediaPosition properties
    function get_Duration(out plength: TRefTime): HResult; stdcall;
    function put_CurrentPosition(llTime: TRefTime): HResult; stdcall;
    function get_CurrentPosition(out pllTime: TRefTime): HResult; stdcall;
    function get_StopTime(out pllTime: TRefTime): HResult; stdcall;
    function put_StopTime(llTime: TRefTime): HResult; stdcall;
    function get_PrerollTime(out pllTime: TRefTime): HResult; stdcall;
    function put_PrerollTime(llTime: TRefTime): HResult; stdcall;
    function put_Rate(dRate: double): HResult; stdcall;
    function get_Rate(out pdRate: double): HResult; stdcall;
    function CanSeekForward(out pCanSeekForward: Longint): HResult; stdcall;
    function CanSeekBackward(out pCanSeekBackward: Longint): HResult; stdcall;
  end;

  TBCRendererPosPassThru = class(TBCPosPassThru)
  protected
    FPositionLock: TBCCritSec; // Locks access to our position
    FStartMedia  : Int64;      // Start media time last seen
    FEndMedia    : Int64;      // And likewise the end media
    FReset       : boolean;    // Have media times been set
  public
    // Used to help with passing media times through graph
    constructor Create(name: String; Unk: IUnknown; out hr: HRESULT; Pin: IPin); reintroduce;
    destructor destroy; override;

    function RegisterMediaTime(MediaSample: IMediaSample): HRESULT; overload;
    function RegisterMediaTime(StartTime, EndTime: int64): HRESULT; overload;
    function GetMediaTime(out StartTime, EndTime: int64): HRESULT; override;
    function ResetMediaTime: HRESULT;
    function EOS: HRESULT;
  end;

  // wrapper for event objects
  TBCAMEvent = class
  protected
    FEvent: THANDLE;
  public
    constructor Create(ManualReset: boolean = false);
    destructor destroy; override;
    property Handle: THandle read FEvent;
    procedure SetEv;
    function Wait(Timeout: Cardinal = INFINITE): boolean;
    procedure Reset;
    function Check: boolean;
  end;

  TBCTimeoutEvent = TBCAMEvent;

  // wrapper for event objects that do message processing
  // This adds ONE method to the CAMEvent object to allow sent
  // messages to be processed while waiting
  TBCAMMsgEvent = class(TBCAMEvent)
  public
    // Allow SEND messages to be processed while waiting
    function WaitMsg(Timeout: DWord = INFINITE): boolean;
  end;

  // support for a worker thread
  // simple thread class supports creation of worker thread, synchronization
  // and communication. Can be derived to simplify parameter passing
  TThreadProc = function: DWORD of object;

  TBCAMThread = class
  private
    FEventSend: TBCAMEvent;
    FEventComplete: TBCAMEvent;
    FParam: DWord;
    FReturnVal: DWord;
    FThreadProc: TThreadProc;
  protected
    FThread: THandle;

    // thread will run this function on startup
    // must be supplied by derived class
    function ThreadProc: DWord; virtual;
  public
    FAccessLock: TBCCritSec; // locks access by client threads
    FWorkerLock: TBCCritSec; // locks access to shared objects
    constructor Create;
    destructor Destroy; override;


    // thread initially runs this. param is actually 'this'. function
    // just gets this and calls ThreadProc
    function InitialThreadProc(p: Pointer): DWORD; virtual; stdcall;  // WINAPI;

    // start thread running  - error if already running
    function Create_: boolean;

    // signal the thread, and block for a response
    //
    function CallWorker(Param: DWORD): DWORD;

    // accessor thread calls this when done with thread (having told thread
    // to exit)
    procedure Close;

    // ThreadExists
    // Return True if the thread exists. FALSE otherwise
    function ThreadExists: boolean; // const

    // wait for the next request
    function GetRequest: DWORD;

    // is there a request?
    function CheckRequest(Param: PDWORD): boolean;

    // reply to the request
    procedure Reply(v: DWORD);

    // If you want to do WaitForMultipleObjects you'll need to include
    // this handle in your wait list or you won't be responsive
    function GetRequestHandle: THANDLE;

    // Find out what the request was
    function GetRequestParam: DWORD;

    // call CoInitializeEx (COINIT_DISABLE_OLE1DDE) if
    // available. S_FALSE means it's not available.
    class function CoInitializeHelper: HRESULT;
  end;



  TBCRenderedInputPin = class(TBCBaseInputPin)
  private
    procedure DoCompleteHandling;
  protected
    // Member variables to track state
    FAtEndOfStream    : boolean; // Set by EndOfStream
    FCompleteNotified : boolean; // Set when we notify for EC_COMPLETE
  public
    constructor Create(ObjectName: string; Filter: TBCBaseFilter;
      Lock: TBCCritSec; out hr: HRESULT; Name: WideString);

    // Override methods to track end of stream state
    function EndOfStream: HRESULT; override; stdcall;
    function EndFlush: HRESULT; override; stdcall;

    function Active: HRESULT; override;
    function Run(Start: TReferenceTime): HRESULT; override;
  end;


(* A generic list of pointers to objects.
   No storage management or copying is