Fmt                    : TAMMediaType;   // Media type of connection

    FStart                 : TReferenceTime;  // time from NewSegment call
    FStop                  : TReferenceTime;  // time from NewSegment
    FRate                  : double;           // rate from NewSegment

    FRef                   : LongInt;
    function GetCurrentMediaType: TBCMediaType;
    function GetAMMediaType: PAMMediaType;
  protected
    procedure DisplayPinInfo(ReceivePin: IPin);
    procedure DisplayTypeInfo(Pin: IPin; pmt: PAMMediaType);

    // used to agree a media type for a pin connection
    // given a specific media type, attempt a connection (includes
    // checking that the type is acceptable to this pin)
    function AttemptConnection(
       ReceivePin: IPin;      // connect to this pin
       pmt       : PAMMediaType // using this type
       ): HRESULT;
    // try all the media types in this enumerator - for each that
    // we accept, try to connect using ReceiveConnection.
    function TryMediaTypes(
               ReceivePin: IPin;           // connect to this pin
               pmt       : PAMMediaType;     // proposed type from Connect
               Enum      : IEnumMediaTypes // try this enumerator
               ): HRESULT;

    // establish a connection with a suitable mediatype. Needs to
    // propose a media type if the pmt pointer is null or partially
    // specified - use TryMediaTypes on both our and then the other pin's
    // enumerator until we find one that works.
    function AgreeMediaType(
               ReceivePin: IPin;      // connect to this pin
               pmt       : PAMMediaType // proposed type from Connect
               ): HRESULT;
    function DisconnectInternal: HRESULT; stdcall;
  public
    function NonDelegatingAddRef: Integer; override; stdcall;
    function NonDelegatingRelease: Integer; override; stdcall;
    constructor Create(
                  ObjectName: string;           // Object description
                  Filter    : TBCBaseFilter;      // Owning filter who knows about pins
                  Lock      : TBCCritSec;         // Object who implements the lock
                  out hr    : HRESULT;          // General OLE return code
                  Name      : WideString;       // Pin name for us
                  dir       : TPinDirection);  // Either PINDIR_INPUT or PINDIR_OUTPUT
    destructor destroy; override;
    // --- IPin methods ---
    // take lead role in establishing a connection. Media type pointer
    // may be null, or may point to partially-specified mediatype
    // (subtype or format type may be GUID_NULL).
    function Connect(pReceivePin: IPin; const pmt: PAMMediaType): HRESULT; virtual; stdcall;
    // (passive) accept a connection from another pin
    function ReceiveConnection(pConnector: IPin; const pmt: TAMMediaType): HRESULT; virtual; stdcall;
    function Disconnect: HRESULT; virtual; stdcall;
    function ConnectedTo(out pPin: IPin): HRESULT; virtual; stdcall;
    function ConnectionMediaType(out pmt: TAMMediaType): HRESULT; virtual; stdcall;
    function QueryPinInfo(out pInfo: TPinInfo): HRESULT; virtual; stdcall;
    function QueryDirection(out pPinDir: TPinDirection): HRESULT; stdcall;
    function QueryId(out Id: PWideChar): HRESULT; virtual; stdcall;
    // does the pin support this media type
    function QueryAccept(const pmt: TAMMediaType): HRESULT; virtual; stdcall;
    // return an enumerator for this pins preferred media types
    function EnumMediaTypes(out ppEnum: IEnumMediaTypes): HRESULT; virtual; stdcall;
    // return an array of IPin* - the pins that this pin internally connects to
    // All pins put in the array must be AddReffed (but no others)
    // Errors: "Can't say" - FAIL, not enough slots - return S_FALSE
    // Default: return E_NOTIMPL
    // The filter graph will interpret NOT_IMPL as any input pin connects to
    // all visible output pins and vice versa.
    // apPin can be NULL if nPin==0 (not otherwise).
    function QueryInternalConnections(out apPin: IPin; var nPin: ULONG): HRESULT; virtual; stdcall;
    // Called when no more data will be sent
    function EndOfStream: HRESULT; virtual; stdcall;
    function BeginFlush: HRESULT; virtual; stdcall; abstract;
    function EndFlush: HRESULT; virtual; stdcall; abstract;
    // Begin/EndFlush still PURE

    // NewSegment notifies of the start/stop/rate applying to the data
    // about to be received. Default implementation records data and
    // returns S_OK.
    // Override this to pass downstream.
    function NewSegment(tStart, tStop: TReferenceTime; dRate: double): HRESULT; virtual; stdcall;
    // --- IQualityControl methods ---
    function Notify(pSelf: IBaseFilter; q: TQuality): HRESULT; virtual; stdcall;
    function SetSink(piqc: IQualityControl): HRESULT; virtual; stdcall;
    // --- helper methods ---

    // Returns True if the pin is connected. false otherwise.
    function IsConnected: boolean;
    // Return the pin this is connected to (if any)
    property GetConnected: IPin read FConnected;
    // Check if our filter is currently stopped
    function IsStopped: boolean;
    // find out the current type version (used by enumerators)
    function GetMediaTypeVersion: longint; virtual;
    procedure IncrementTypeVersion;
    // switch the pin to active (paused or running) mode
    // not an error to call this if already active
    function Active: HRESULT; virtual;
    // switch the pin to inactive state - may already be inactive
    function Inactive: HRESULT; virtual;
    // Notify of Run() from filter
    function Run(Start: TReferenceTime): HRESULT; virtual;
    // check if the pin can support this specific proposed type and format
    function CheckMediaType(mt: PAMMediaType): HRESULT; virtual; abstract;
    // set the connection to use this format (previously agreed)
    function SetMediaType(mt: PAMMediaType): HRESULT; virtual;
    // check that the connection is ok before verifying it
    // can be overridden eg to check what interfaces will be supported.
    function CheckConnect(Pin: IPin): HRESULT; virtual;
    // Set and release resources required for a connection
    function BreakConnect: HRESULT; virtual;
    function CompleteConnect(ReceivePin: IPin): HRESULT; virtual;
    // returns the preferred formats for a pin
    function GetMediaType(Position: integer; out MediaType: PAMMediaType): HRESULT; virtual;
    // access to NewSegment values
    property CurrentStopTime: TReferenceTime read FStop;
    property CurrentStartTime: TReferenceTime read FStart;
    property CurrentRate: double read FRate;
    //  Access name
    property Name: WideString read FPinName;
    property CanReconnectWhenActive: boolean read FCanReconnectWhenActive write FCanReconnectWhenActive;
    // Media type
    property CurrentMediaType: TBCMediaType read GetCurrentMediaType;
    property AMMediaType: PAMMediaType read GetAMMediaType;
  end;

  TBCEnumPins = class(TInterfacedObject, IEnumPins)
  private
    FPosition: integer;   // Current ordinal position
    FPinCount: integer;   // Number of pins available
    FFilter: TBCBaseFilter; // The filter who owns us
    FVersion: LongInt;    // Pin version information
    // These pointers have not been AddRef'ed and
    // so they should not be dereferenced.  They are
    // merely kept to ID which pins have been enumerated.
    FPinCache: TList;
    { If while we are retrieving a pin for example from the filter an error
      occurs we assume that our internal state is stale with respect to the
      filter (someone may have deleted all the pins). We can check before
      starting whether or not the operation is likely to fail by asking the
      filter what it's current version number is. If the filter has not
      overriden the GetPinVersion method then this will always match }
    function AreWeOutOfSync: boolean;

    (* This method performs the same operations as Reset, except is does not clear
       the cache of pins already enumerated. *)
    function Refresh: HRESULT; stdcall;
  public
    constructor Create(Filter: TBCBaseFilter; EnumPins: TBCEnumPins);
    destructor Destroy; override;

    function Next(cPins: ULONG;  // place this many pins...
      out ppPins: IPin;          // ...in this array of IPin*
      pcFetched: PULONG          // actual count passed returned here
      ): HRESULT; stdcall;
    function Skip(cPins: ULONG): HRESULT; stdcall;
    function Reset: HRESULT; stdcall;
    function Clone(out ppEnum: IEnumPins): HRESULT; stdcall;
  end;

  TBCEnumMediaTypes = class(TInterfacedObject, IEnumMediaTypes)
  private
   FPosition: Cardinal;   // Current ordinal position
   FPin     : TBCBasePin; // The pin who owns us
   FVersion : LongInt;    // Media type version value
   function AreWeOutOfSync: boolean;
  public
    constructor Create(Pin: TBCBasePin; EnumMediaTypes: TBCEnumMediaTypes);
    destructor Destroy; override;
    function Next(cMediaTypes: ULONG; out ppMediaTypes: PAMMediaType;
      pcFetched: PULONG): HRESULT; stdcall;
    function Skip(cMediaTypes: ULONG): HRESULT; stdcall;
    function Reset: HRESULT; stdcall;
    function Clone(out ppEnum: IEnumMediaTypes): HRESULT; stdcall;
  end;


  TBCBaseOutputPin = class(TBCBasePin)
  protected
    FAllocator: IMemAllocator;
    // interface on the downstreaminput pin, set up in CheckConnect when we connect.
    FInputPin : IMemInputPin;
  public
    constructor Create(ObjectName: string; Filter: TBCBaseFilter; Lock: TBCCritSec;
      out hr: HRESULT; const Name: WideString);

    // override CompleteConnect() so we can negotiate an allocator
    function CompleteConnect(ReceivePin: IPin): HRESULT; override;
    // negotiate the allocator and its buffer size/count and other properties
    // Calls DecideBufferSize to set properties
    function DecideAllocator(Pin: IMemInputPin; out Alloc: IMemAllocator): HRESULT; virtual;
    // override this to set the buffer size and count. Return an error
    // if the size/count is not to your liking.
    // The allocator properties passed in are those requested by the
    // input pin - use eg the alignment and prefix members if you have
    // no preference on these.
    function DecideBufferSize(Alloc: IMemAllocator; propInputRequest: PAllocatorProperties): HRESULT; virtual;

    // returns an empty sample buffer from the allocator
    function GetDeliveryBuffer(out Sample: IMediaSample; StartTime: PReferenceTime;
      EndTime: PReferenceTime; Flags: Longword): HRESULT; virtual;

    // deliver a filled-in sample to the connected input pin
    // note - you need to release it after calling this. The receiving
    // pin will addref the sample if it needs to hold it beyond the
    // call.
    function Deliver(Sample: IMediaSample): HRESULT; virtual;

    // override this to control the connection
    function InitAllocator(out Alloc: IMemAllocator): HRESULT; virtual;
    function CheckConnect(Pin: IPin): HRESULT; override;
    function BreakConnect: HRESULT; override;

    // override to call Commit and Decommit
    function Active: HRESULT; override;
    function Inactive: HRESULT; override;

    // we have a default handling of EndOfStream which is to return
    // an error, since this should be called on input pins only
    function EndOfStream: HRESULT; override; stdcall;

    // called from elsewhere in our filter to pass EOS downstream to
    // our connected input pin
    function DeliverEndOfStream: HRESULT; virtual;

    // same for Begin/EndFlush - we handle Begin/EndFlush since it
    // is an error on an output pin, and we have Deliver methods to
    // call the methods on the connected pin
    function BeginFlush: HRESULT; override; stdcall;
    function EndFlush: HRESULT; override; stdcall;
    function DeliverBeginFlush: HRESULT; virtual;
    function DeliverEndFlush: HRESULT; virtual;

    // deliver NewSegment to connected pin - you will need to
    // override this if you queue any data in your output pin.
    function DeliverNewSegment(Start, Stop: TReferenceTime; Rate: double): HRESULT; virtual;
  end;

  TBCBaseInputPin = class(TBCBasePin, IMemInputPin)
  protected
    FAllocator: IMemAllocator;    // Default memory allocator
    // allocator is read-only, so received samples
    // cannot be modified (probably only relevant to in-place
    // transforms
    FReadOnly: boolean;

    //private:  this should really be private... only the MPEG code
    // currently looks at it directly and it should use IsFlushing().
    // in flushing state (between BeginFlush and EndFlush)
    // if True, all Receives are returned with S_FALSE
    FFlushing: boolean;

    // Sample properties - initalized in Receive

    FSampleProps: TAMSample2Properties;

  public

    constructor Create(ObjectName: string; Filter: TBCBaseFilter;
      Lock: TBCCritSec; out hr: HRESULT; Name: WideString);
    destructor Destroy; override;

    // ----------IMemInputPin--------------
    // return the allocator interface that this input pin
    // would like the output pin to use
    function GetAllocator(out ppAllocator: IMemAllocator): HRESULT; stdcall;
    // tell the input pin which allocator the output pin is actually
    // going to use.
    function NotifyAllocator(pAllocator: IMemAllocator; bReadOnly: BOOL): HRESULT; stdcall;
    // this method is optional (can return E_NOTIMPL).
    // default implementation returns E_NOTIMPL. Override if you have
    // specific alignment or prefix needs, but could use an upstream
    // allocator
    function GetAllocatorRequirements(out pProps: TAllocatorProperties): HRESULT; stdcall;
    // do something with this media sample
    function Receive(pSample: IMediaSample): HRESULT; virtual; stdcall;
    // do something with these media samples
    function ReceiveMultiple(var pSamples: IMediaSample; nSamples: Longint;
        out nSamplesProcessed: Longint): HRESULT; stdcall;
     // See if Receive() blocks
    function ReceiveCanBlock: HRESULT; stdcall;

    //-----------Helper-------------
    // Default handling for BeginFlush - call at the beginning
    // of your implementation (makes sure that all Receive calls