ZPlay.SetCallbackFunc Method

Set callback function.

Pascal

function SetCallbackFunc(CallbackFunc: TCallbackFunc; Messages: TCallbackMessage; UserData: Integer): Boolean;

Parameters

Parameters	Description
CallbackFunc: TCallbackFunc	Address to callback function. Set this value to 0 to disable callback mechanism.
Messages: TCallbackMessage	Specify messages you need to receive with callback function. This parameter can be combination of multiple callback messages.
UserData: Integer	User data. This value will be passed to CallbackFunc as parameter.

Return Values

Return Values	Description
True	All OK.
False	Error. To get error message read here.

Remarks

All callback messages are sent from decoding thread.

There are 2 types of callback messages, blocking (sync) and not blocking (async).

Blocking message will block decoding thread until callback function returns. Non blocking mesage will not block decoding thread.

Warning: callback function must have __stdcall calling convention.

Note: You must protect CallbackFunc from garbage collector. Use global or static variable to keep alive callback function all the time. If you don't protect CallbackFunc, garbage collector will destroy or move this function and you will get memory access error when next callback event occurrs.

See Also

TCallbackFunc

Example


// callback function

Function player_callback(objptr: Pointer; user_data: Integer; msg: TCallbackMessage; param1: Cardinal; param2: Cardinal):Integer;stdcall;
var
  ReadBytes: Integer;
beginResult := 0;
   case msg of
      libZPlay.MsgStreamNeedMoreDataAsync:
      begin
      // managed stream, read more data
        if FileHandle = 0 then
        begin
          player.PushDataToStream(nil, 0);
          Exit;
        end;

        if Buffer = nil then
        begin
          player.PushDataToStream(nil, 0);
          Exit;
        end;
        // read next data from file
        ReadBytes := FileRead(FileHandle, Buffer^, ChunkSize);
        if ReadBytes = 0 then
        begin
          player.PushDataToStream(nil, 0);
          Exit;
        end;
        // push new data to stream
        player.PushDataToStream(Buffer, ReadBytes);
      end;
   end;
Result := 0;
end;

// ...

if player.SetCallbackFunc(Addr(player_callback), TCallbackMessage(libZPlay.MsgStreamNeedMoreDataAsync) , 0) = false then
begin
  MessageBox(0, PAnsiChar(player.GetError()), 'Fatal error' ,0);
end;

Group

ZPlay Methods

Web: http://libzplay.sourceforge.net/

Email: zcindori@inet.hr

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