Question:
How can I determine the bitrate of a *.WAV file?
Answer:
Use the MCI and follow these steps:
open the file: TForm1.OpenMedia using MCI_OPEN
obtain the desired status information: TForm1.GetStatus using MCI_STATUS
then close it: TForm1.CloseMedia using MCI_CLOSE
The unit below shows how it's done.
unit fMain;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
OpenDialog1: TOpenDialog;
ListBox1: TListBox;
procedure Button1Click(Sender: TObject);
private
{ private declarations }
procedure OpenMedia(WaveFile: string);
function GetStatus(StatusRequested: DWord) : LongInt;
procedure CloseMedia;
public
{ public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
uses
MMSystem;
var
MyError,
dwFlags: LongInt;
FDeviceID: Word;
procedure TForm1.OpenMedia(WaveFile: string);
var
MyOpenParms: TMCI_Open_Parms;
begin { TForm1.OpenMedia }
with MyOpenParms do
begin
dwCallback := Handle; // TForm1.Handle
lpstrDeviceType := PChar('WaveAudio');
lpstrElementName := PChar(WaveFile)
end; { with MyOpenParms }
dwFlags := MCI_WAIT or MCI_OPEN_ELEMENT or MCI_OPEN_TYPE;
MyError := mciSendCommand(0, MCI_OPEN, dwFlags, LongInt(@MyOpenParms));
// one could use mciSendCommand(DevId, here to specify a particular device
if MyError=0 then
FDeviceID := MyOpenParms.wDeviceID
else
raise Exception.Create('Open Failed')
end; { TForm1.OpenMedia }
function TForm1.GetStatus(StatusRequested: DWord) : LongInt;
var
MyStatusParms: TMCI_Status_Parms;
begin { TForm1.GetStatus }
dwFlags := MCI_WAIT or MCI_STATUS_ITEM;
with MyStatusParms do
begin
dwCallback := Handle;
dwItem := StatusRequested
end; { with MyStatusParms }
MyError := mciSendCommand(FDeviceID, MCI_STATUS, MCI_WAIT or MCI_STATUS_ITEM,
LongInt(@MyStatusParms));
if MyError=0 then
Result := MyStatusParms.dwReturn
else
raise Exception.Create('Status call to get status of ' + IntToStr(StatusRequested)
+ ' Failed')
end; { TForm1.GetStatus }
procedure TForm1.CloseMedia;
var
MyGenParms: TMCI_Generic_Parms;
begin { TForm1.CloseMedia }
if FDeviceID>0 then
begin
dwFlags := 0;
MyGenParms.dwCallback := Handle; // TForm1.Handle
MyError := mciSendCommand(FDeviceID, MCI_CLOSE, dwFlags, LongInt(@MyGenParms));
if MyError=0 then
FDeviceID := 0
else
begin
raise Exception.Create('Close Failed')
end; { not (MyError=0) }
end; { FDeviceID>0 }
end; { TForm1.CloseMedia }
procedure TForm1.Button1Click(Sender: TObject);
begin { TForm1.Button1Click }
if OpenDialog1.Execute then
begin
OpenMedia(OpenDialog1.FileName);
with ListBox1.Items do
begin
Clear;
Add(OpenDialog1.FileName);
Add('Average Bytes / Sec : ' + IntToStr(GetStatus(MCI_WAVE_STATUS_AVGBYTESPERSEC)));
Add('Bits / Sample : ' + IntToStr(GetStatus(MCI_WAVE_STATUS_BITSPERSAMPLE)));
Add('Samples / Sec : ' + IntToStr(GetStatus(MCI_WAVE_STATUS_SAMPLESPERSEC)));
Add('Channels : ' + IntToStr(GetStatus(MCI_WAVE_STATUS_CHANNELS)))
end; { with ListBox1.Items }
CloseMedia
end; { OpenDialog1.Execute }
end; { TForm1.Button1Click }
end.