Mega Code Archive
Build an MP3 Player
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Title: Build an MP3 Player
Question: The mciSendString function sends a command string to an MCI device. The device that the command is sent to is specified in the command string; but how to map the function ?
Answer:
The operations are found in
Winmm.lib and as a DLL in Winmm.dll
using a simple wav you call also the winmm.dll
//function PlaySound(s: pchar; flag, syncflag: integer): boolean;
//external 'PlaySound@winmm.dll stdcall';
But we want to play mp3 with the MCI.
The Media Control Interface (MCI) provides standard commands for playing multimedia devices and recording multimedia resource files. These commands are a generic interface to nearly every kind of multimedia device.
I map at first 3 functions and 1 procedure to call the mciSendString (say it a command string):
procedure playMP3(mp3path: string);
begin
mciSendString(PChar('open "' + mp3path + '" alias MP3'), NIL, 0, 0);
//player.handle
mciSendString('play MP3', NIL, 0, 0);
//mciSendString('close MP3', 0,0,0);
end;
procedure stopMP3;
begin
mciSendString('stop MP3', 0,0,0);
end;
procedure closeMP3;
begin
mciSendString('close MP3', 0,0,0);
end;
function lengthmp3(mp3path: string):integer;
var nlength: string;
begin
mciSendString(PChar('open "' + mp3path + '" alias MP3'), NIL, 0, 0);
setlength(nlength, 255);
mciSendString('status MP3 length', pchar(nlength), length(nlength), 0);
result:= StrToInt(nlength);
end;
The first parameter is always a pointer to a null-terminated string that specifies an MCI command string. For a list, see Multimedia Command Strings at:
http://msdn.microsoft.com/en-us/library/dd743572(v=VS.85).aspx
Next I put some code around the mapped procedures:
for i:= 0 to lstbox.items.count - 1 do begin
mp3time:= lengthmp3(lstbox.items[i])
writeln(Format('%s',[lstbox.items[i]+MSecToTime(mp3time)]));
LetLogoDraw(inFrm.Canvas, 10, 5, 3, clpurple);
playmp3(lstbox.items[i])
sleep(mp3time)
closemp3;
end;
The whole player is found at:
http://www.softwareschule.ch/download/88_pas_soundbox2_mp3.txt
the GUI of the Player in the box:
http://www.softwareschule.ch/download/maxboxgui29.png
its a script which runs in maXbox but the concept is ready to run in Delphi or FreePascal too.
http://sourceforge.net/projects/maxbox/
by the way: mp3 and shuffle is close behind, the best shuffle code is from Don Knuth (elegant and efficient):
procedure Shuffle(vQ: TStringList);
var j, k: integer;
tmp: String;
begin
randomize;
for j:= vQ.count -1 downto 0 do begin
k:= Random(j+1);
tmp:= (vQ[j]);
vQ[j]:= vQ[k];
vQ[k]:= tmp;
end;
end;
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