Delphi:加载BASS DLL并播放MP3

Question

我想从某个地方手动加载一个低音DLL,然后播放一个mp3文件.怎么做？德尔福XE2.

我的尝试不起作用:

type
  QWORD = Int64;
  HSTREAM = LongWord;
type
  TBASS_ChannelPlay = function(handle: HSTREAM; restart: LongBool): LongBool; stdcall;

type
  TBASS_StreamCreateFile = function(mem: LongBool; f: Pointer;
    offset, length: QWORD; flags: LongWord): HSTREAM; stdcall;

procedure PlayMP3(FileName: string);
var
  BASS_ChannelPlay: TBASS_ChannelPlay;
  BASS_StreamCreateFile: TBASS_StreamCreateFile;
  DllHandle: THandle;
  MP3Stream: HSTREAM;
  DllPath:string;
  pFileName:pchar;
begin
  DllPath:= 'c:\dll\bass.dll';
  DllHandle := LoadLibrary(pchar(DLLPath));
  try
    if DllHandle = 0 then
      Exit;
    @BASS_StreamCreateFile := GetProcAddress(DllHandle,
      'BASS_StreamCreateFile');
    if @BASS_StreamCreateFile <> nil then
    begin
      pfilename:=pchar(FileName);
      MP3Stream := BASS_StreamCreateFile(false, Pfilename, 0, 0, 0);
      if MP3Stream <> 0 then
      begin
        @BASS_ChannelPlay := GetProcAddress(DllHandle, 'BASS_ChannelPlay');
        if @BASS_ChannelPlay <> nil then
          BASS_ChannelPlay(MP3Stream,false);
      end;
    end;
  finally
    FreeLibrary(DllHandle);
  end;
end;

但是BASS_StreamCreateFile一直返回0 :(

他们的例子(Bass Test)和Bass.pas中的代码:

type
  DWORD = LongWord;
  BOOL = LongBool;
  QWORD = Int64;
  HSTREAM = DWORD;

function BASS_StreamCreateFile(mem: BOOL; f: Pointer; offset, length: QWORD; flags: DWORD): HSTREAM; {$IFDEF WIN32}stdcall{$ELSE}cdecl{$ENDIF}; external bassdll;

strs: array[0..128] of HSTREAM;

procedure TForm1.Button15Click(Sender: TObject);
var
    f: PChar;
begin
    if not OpenDialog2.Execute then Exit;
    f := PChar(OpenDialog2.FileName);
    strs[strc] := BASS_StreamCreateFile(False, f, 0, 0, 0 {$IFDEF UNICODE} or BASS_UNICODE {$ENDIF});
    if strs[strc] <> 0 then
    begin
        ListBox3.Items.Add(OpenDialog2.FileName);
        Inc(strc);
    end
    else
        Error('Error creating stream!');
end;

添加

  MP3Stream := BASS_StreamCreateFile(false, Pfilename, 0, 0, 0);
  ShowMessage(SysErrorMessage(GetLastError));

GetLastError 没有显示任何错误!

添加

还有BASS 2.4 Delphi单元(动态).

它写道:

如何安装将DYNAMIC_BASS.PAS复制到Delphi路径或项目目录的\ LIB子目录中调用Load_BASSDLL(例如在FormCreate中)以在使用任何函数之前加载BASS,并在您使用
Unload_BASSDLL(例如在FormDestory中)卸载它时重做.

注意:Delphi 2009用户应尽可能使用BASS_UNICODE标志

我做:

 if Load_BASSDLL(DllPath) then
  begin
  FileName:='C:\Users\V\Desktop\cmd.mp3';
  MP3Stream:=BASS_StreamCreateFile(False, pchar(FileName), 0, 0, 0 {$IFDEF UNICODE} or BASS_UNICODE {$ENDIF});
    if MP3Stream <> 0 then
     BASS_ChannelPlay(MP3Stream, False);
     Unload_BASSDLL;
  end;

它仍然不起作用:(

添加:

如果要这样做

BASS_Init(-1, 44100, 0, Form1.Handle, nil);

然后BASS_ChannelPlay(MP3Stream, False)返回true但我听不到声音:(

Answer 1

你错过了电话BASS_Init.从您引用的相同演示中,在以下情况FormCreate中:

// Initialize audio - default device, 44100hz, stereo, 16 bits
if not BASS_Init(-1, 44100, 0, Handle, nil) then
  Error('Error initializing audio!'); 

另外,看一下demo源的调用:

BASS_StreamCreateFile(False, f, 0, 0, 
 0 {$IFDEF UNICODE} or BASS_UNICODE {$ENDIF});

注意最后一个参数会发生什么？在or BASS_UNICODE需要对D2009及以上的,除非你使用PAnsiChar的替代PChar; Delphi的默认字符串类型是UnicodeString,默认PChar为PWideChar.

您可以在有{$IFDEF UNICODE}或没有它的情况下使用它; Delphi定义UNICODE,所以如果你使用它,你的代码也将与早期版本的Delphi(pre-D2009)向后兼容.

您还应该查看dynamic_bass.pas该Bass\Delphi\dynamic文件夹.它有代码来动态加载库并检索所有函数; 如果你不想直接使用它,至少你可以从那里复制你需要的函数定义和动态加载代码.