delphi 获取Wav文件的长度

如何在不使用TMediaPlayer打开文件的情况下获取Wav文件的长度？

使用MCI_SENDSTRING API调用可以获取长度，但这确实涉及到。但是，已经提出了一种更好的方法，可以直接访问文件并解释其自身的内部数据以获得信息。

这是函数：

function GetWaveLength(WaveFile: string): Double;

var

  groupID: array[0..3] of char;

  riffType: array[0..3] of char;

  BytesPerSec: Integer;

  Stream: TFileStream;

  dataSize: Integer;

  // chunk seeking function,

  // -1 means: chunk not found

function GotoChunk(ID: string): Integer;

var

  chunkID: array[0..3] of char;

  chunkSize: Integer;

begin

  Result := -1;

  with Stream do

    begin

      // index of first chunk

      Position := 12;

      repeat

        // read next chunk

        Read(chunkID, 4);

        Read(chunkSize, 4);

        if chunkID <> ID then

         // skip chunk

         Position := Position + chunkSize;

      until (chunkID = ID) or (Position >= Size);

      if chunkID = ID then

        // chunk found,

        // return chunk size

        Result := chunkSize;

    end;

  end;

  begin

    Result := -1;

    Stream := TFileStream.Create(WaveFile, fmOpenRead or fmShareDenyNone);

    with Stream do

      try

        Read(groupID, 4);

        Position := Position + 4; // skip four bytes (file size)

        Read(riffType, 4);

        if (groupID = 'RIFF') and (riffType = 'WAVE') then

          begin

            // search for format chunk

            if GotoChunk('fmt') <> -1 then

              begin

                // found it

                Position := Position + 8;

                Read(BytesPerSec,4);

                //search for data chunk

                dataSize := GotoChunk('data');

                if dataSize <> -1 then

                  // found it

                  Result := dataSize / BytesPerSec

              end

          end

      finally

        Free;

      end;

end;

This returns the number of seconds as a floating point number, which is not necessarily the most helpful format.  Far better to return it as a string  representing the time in hours, minutes and seconds.  The following function achieves this based on the number of seconds as an integer:

function SecondsToTimeStr(RemainingSeconds: Integer):String;

var

  Hours, Minutes, Seconds: Integer;

  HourString, MinuteString, SecondString: String;

begin

  // Calculate Minutes

  Seconds := RemainingSeconds mod 60;

  Minutes := RemainingSeconds div 60;

  Hours := Minutes div 60;

  Minutes := Minutes-(Hours*60);

  if Hours < 10  then

    HourString := '0'+IntToStr(Hours)+':'

  else

    HourString := IntToStr(Hours)+':';

  if Minutes < 10 then

    MinuteString := '0'+ IntToStr(Minutes)+':'

  else

    MinuteString := IntToStr(Minutes)+':';

  if Seconds <10 then

    SecondString := '0'+ IntToStr(Seconds)

  else

    SecondString := IntToStr(Seconds);

  Result := HourString+MinuteString+SecondString;

end;

这将返回秒数作为浮点数，这不一定是最有用的格式。最好以字符串形式返回它，以小时，分钟和秒为单位。以下函数基于秒数（整数）实现此目的：

procedure TForm1.Button1Click(Sender: TObject);

var

  Seconds: Integer;

begin

  Seconds := Trunc(GetWaveLength(Edit1.Text));//gets only the Integer part of the length

  Label1.Caption := SecondsToTimeStr(Seconds);

end;

创建完这些功能后，您可以从任何相关事件中调用它们，例如单击按钮：

procedure TForm1.Button1Click(Sender: TObject);

begin

  Label1.Caption := SecondsToTimeStr(Trunc(GetWaveLength(Edit1.Text)));

end;