怎样获得mp3的ID3Tag的持续时间(50分)

怎样获得mp3的ID3Tag的持续时间？

{
----------------------------------------------------------
MAS-CompMaker was used to generate this code
MAS-CompMaker, 2000-2001?Mats Asplund
----------------------------------------------------------

Component Name: Tmp3Tag
Author: Slightly improved and redone from a class made by
Andrey V. Sorokin, into a component by Mats Asplund.
Creation: 2001-11-08
Version: 1.0
Description: A component for reading and writing mp3-tags.
Credit: Andrey V.Sorokin
Saint-Petersburg, Russia
anso@mail.ru
anso@usa.net
http://anso.da.ru
http://anso.virtualave.net
E-mail: masprod@telia.com
Site: http://go.to/masdp
Legal issues: Copyright(c) 1999,2000 by Andrey V.Sorokin.
All rights reserved 2001?by Mats Asplund.

Usage:
This software is provided 'as-is', without any express or
implied warranty. In no event will the author be held liable
for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any
purpose, including commercial applications, and to alter it
and redistribute it freely, subject to the following
restrictions:

1. The origin of this software must not be misrepresented,
you must not claim that you wrote the original software.
If you use this software in a product, an acknowledgment
in the productdo
cumentation would be appreciated but is
not required.

2. Altered source versions must be plainly marked as such, and
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source
distribution.

4. If you decide to use this software in any of your applications.
Send me an EMail and tell me about it.

Quick Reference:

Tmp3Tag inherits from TComponent.

Key-Properties:

TagPresent: True if loaded tag seems to be OK.

TagModified: True if anything changed.

v1Tag: True if ID3v1, false if ID3v1.1

Title: Music title

Artist: Performer

Year: Year as 4-chars string.

Album: Album title

Track: Track number (only if not v1)

Comment: Comment

GenreID: Genre ID (see fID3Genres which contains genres list as
TStrings)

Genre: Genre as string


Key-Methods:

LoadTag: Load tag from ABuf (max ABufSz)

LoadTagFromStream: Find ID3tag in AStream (max AStreamSz bytes from current
position) and Load it. If success then
returns offset to
tag, else
-1.

LoadTagFromFile: Load ID3Tag from file AFileName

SaveTag: Write tag into ABuf (max ABufSz bytes), clear Modified.

SaveTagToStream: Write tag ito current position of AStream, clear Modified.

SaveTagToFile: Add/Update tag in file AFileName, clear Modified.

DeleteTagFromFile: Delete tag from file AFileName (if it exists).

--------------------------------------------------------------------------------
}
unit mp3Tag;

interface

uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls, ExtCtrls;

type

Tmp3Tag = class(TComponent)
private
fAbout: string;
fModified: Boolean;
fOk: Boolean;
fv1: Boolean;
fTrack: Integer;
fGenreID: Integer;
fArtist: string;
FTitle: string;
fAlbum: string;
fYear: string;
fComment: string;
fGenre: string;
fID3Genres: TStringList;
procedure SetCop(Value: string);
procedure SetGenreID(AGenreID: Integer);
procedure SetTrack(ATrack: Integer);
procedure Setv1(b: Boolean);
procedure SetField(AIdx: Integer;
S: string);
procedure Reset;
procedure SetGenre(const Value: string);
procedure SetID3Genres(const Value: TStringList);
public
constructor Create(AOwner: TComponent);
override;
destructor Destroy;
override;
procedure LoadTag(const ABuf;
ABufSz: Integer);
procedure LoadTagFromStream(AStream: TStream;
AStreamSz: Integer);
procedure LoadTagFromFile(const aFileName: string);
procedure SaveTag(var ABuf;
ABufSz: Integer);
procedure SaveTagToStream(AStream: TStream);
procedure SaveTagToFile(const aFileName: string);
procedure DeleteTagFromFile(const aFileName: string);
published
property TagPresent: Boolean read fOk write fOk;
property TagModified: Boolean read fModified;
property v1Tag: Boolean read fv1 write Setv1;
property Title: string index 1 read FTitle write SetField;
property Artist: string index 2 read fArtist write SetField;
property Year: string index 3 read fYear write SetField;
property Album: string index 4 read fAlbum write SetField;
property Track: Integer read fTrack write SetTrack;
// ID3v1.1 only
property Comment: string index 5 read fComment write SetField;
property GenreID: Integer read fGenreID write SetGenreID;
property Genre: string read fGenre write SetGenre;
property Genres: TStringList read fID3Genres write SetID3Genres;
property About: string read fAbout write SetCop;
end;


procedure Register;

implementation

const
ID3v1TagLen = 128;

procedure Register;
begin

RegisterComponents('MAs Prod.', [Tmp3Tag]);
end;


constructor Tmp3Tag.Create(AOwner: TComponent);
begin

inherited Create(AOwner);
fID3Genres:= TStringList.Create;
fID3Genres.Duplicates:= dupAccept;
fID3Genres.Sorted:= false;
fID3Genres.CommaText:=
'"Blues","Classic Rock","Country","Dance","Disco","Funk","Grunge",'
+ '"Hip-Hop","Jazz","Metal","New Age","Oldies","Other","Pop",'
+ '"R&B","Rap","Reggae","Rock","Techno","Industrial","Alternative",'
+ '"Ska","Death Metal","Pranks","Soundtrack","Euro-Techno","Ambient",'
+ '"Trip-Hop","Vocal","Jazz+Funk","Fusion","Trance","Classical",'
+ '"Instrumental","Acid","House","Game","Sound Clip","Gospel",'
+ '"Noise","AlternRock","Bass","Soul","Punk","Space","Meditative",'
+ '"Instrumental Pop","Instrumental Rock","Ethnic","Gothic",'
+ '"Darkwave","Techno-Industrial","Electronic","Pop-Folk","Eurodance",'
+ '"Dream","Southern Rock","Comedy","Cult","Gangsta","Top 40",'
+ '"Christian Rap","Pop/Funk","Jungle","Native American","Cabaret",'
+ '"New Wave","Psychedelic","Rave","Showtunes","Trailer","Lo-Fi",'
+ '"Tribal","Acid Punk","Acid Jazz","Polka","Retro","Musical",'
+ '"Rock &
Roll","Hard Rock",' // 79 standard genres
+ '"Folk","Folk/Rock","National Folk","Swing","Fast Fusion",'
+ '"Bebob","Latin","Revival","Celtic","Bluegrass","Avantgarde",'
+ '"Gothic Rock","Progressive Rock","Psychedelic Rock",'
+ '"Symphonic Rock","Slow Rock","Big Band","Chorus","Easy Listening",'
+ '"Acoustic","Humour","Speech","Chanson","Opera","Chamber Music",'
+ '"Sonata","Symphony","Booty Bass","Primus","Porn Groove",'
+ '"Satire","Slow Jam","Club","Tango","Samba","Folklore",'
+ '"Ballad","Power Ballad","Rhythmic Soul","Freestyle",'
+ '"Duet","Punk Rock","Drum Solo","Acapella","Euro-House",'
+ '"Dance Hall", "Goa", "Drum &
Bass", "Club-House", "Hardcore",'
+ '"Terror", "Indie", "BritPop", "Negerpunk", "Polsk Punk", "Beat",'
+ '"Christian Gangs", "Heavy Metal", "Black Metal", "Crossover",'
+ '"Contemporary Ch?", "Cristian Rock", "Merengue", "Salsa",'
+ '"Thrash Metal", "Anime", "JPop", "Synthpop", ""';
// 0 .. 93h

fGenreId:= 0;
fGenre:= 'Blues';
fAbout:= 'Version 1.0, 2001?Andrey V.Sorokin &
Mats Asplund';
end;


procedure Tmp3Tag.DeleteTagFromFile(const aFileName: string);
var
F: TStream;
S: string;
begin

F:= TFileStream.Create(aFileName, fmOpenReadWrite or fmShareExclusive);
try
if F.Size >= ID3v1TagLen then

begin

F.Position:= F.Size - ID3v1TagLen;
SetString(S, nil, 3);
F.ReadBuffer(S[1], 3);
if S = 'TAG' then

begin

F.Size:= F.Size - ID3v1TagLen;
end;

end;

finally F.Free;
end;

end;

{ of procedure TID3v1Tag.DeleteFromFile }

destructor Tmp3Tag.Destroy;
begin

inherited Destroy;
end;


procedure Tmp3Tag.LoadTag(const ABuf;
ABufSz: Integer);
var
b: array[0..ID3v1TagLen - 1] of Byte absolute ABuf;
GenreIdx, i: Integer;
function BufStr(APos, ALen: Integer): string;
begin

SetString(Result, nil, ALen);
Move(b[APos], Result[1], ALen);
if Pos(#0, Result) > 0 then

Result:= Copy(Result, 1, Pos(#0, Result) - 1);
Result:= TrimRight(Result);
end;

begin

// save genres IDs for genres list resorting ability
Reset;
for i:= 0 to fID3Genres.Count - 1
do
fID3Genres.Objects:= TObject(i);

fOk:= false;
fModified:= false;
if ABufSz < ID3v1TagLen then
Exit;
if BufStr(0, 3) = 'TAG' then

begin

fOk:= true;
FTitle:= BufStr(3, 30);
fArtist:= BufStr(33, 30);
fAlbum:= BufStr(63, 30);
fYear:= BufStr(93, 4);
fComment:= BufStr(97, 30);
if (b[97 + 28] = 0) and (b[97 + 29] <> 0) then

begin

fv1:= false;
fTrack:= b[97 + 29];
end
else

begin

fv1:= true;
fTrack:= 0;
end;

fGenreID:= b[127];
GenreIdx:= fID3Genres.IndexOfObject(TObject(fGenreID));
if GenreIdx >= 0 then
fGenre:= fID3Genres[GenreIdx]
else
fGenre:= '';
end;

end;

{ of procedure TID3v1Tag.Load }

procedure Tmp3Tag.LoadTagFromFile(const aFileName: string);
var
F: TStream;
begin

F:= TFileStream.Create(aFileName, fmOpenRead or fmShareDenyNone);
try
LoadTagFromStream(F, F.Size);
finally F.Free;
end;

end;

{ of procedure TID3v1Tag.LoadFromFile }

procedure Tmp3Tag.LoadTagFromStream(AStream: TStream;
AStreamSz: Integer);
var
Buf: array[0..ID3v1TagLen - 1] of Byte;
begin

Reset;
if AStreamSz >= ID3v1TagLen then

begin

AStream.Position:= AStream.Position + AStreamSz - ID3v1TagLen;
AStream.ReadBuffer(Buf, ID3v1TagLen);
LoadTag(Buf, ID3v1TagLen);
end
else
fOk:= false;
end;

{ of procedure TID3v1Tag.LoadFromStream }

procedure Tmp3Tag.Reset;
begin

fGenreID:= 94;
{empty string}
fArtist:= '';
FTitle:= '';
fAlbum:= '';
fYear:= '';
fComment:= '';
fGenre:= '';
end;


procedure Tmp3Tag.SaveTag(var ABuf;
ABufSz: Integer);
var
b: array[0..ID3v1TagLen - 1] of Byte absolute ABuf;
procedure StrBuf(APos, ALen: Integer;
const AStr: string);
var
Len: Integer;
begin

Len:= Length(AStr);
if Len > ALen then

Len:= ALen;
Move(AStr[1], b[APos], Len);
if Len < ALen then

FillChar(b[APos + Len], ALen - Len, $20);
end;

begin

if ABufSz < ID3v1TagLen then

raise Exception.Create('TID3v1Tag.Save: Buffer too small');
// fOk ?!!
StrBuf(0, 3, 'TAG');
StrBuf(3, 30, FTitle);
StrBuf(33, 30, fArtist);
StrBuf(63, 30, fAlbum);
StrBuf(93, 4, fYear);
StrBuf(97, 30, fComment);
if not fv1 then

begin

b[97 + 28]:= 0;
b[97 + 29]:= fTrack;
end;

b[127]:= fGenreID;
fModified:= false;
end;

{ of procedure TID3v1Tag.Save }

procedure Tmp3Tag.SaveTagToFile(const aFileName: string);
var
F: TStream;
S: string;
begin

F:= TFileStream.Create(aFileName, fmOpenReadWrite or fmShareDenyNone);
try
if F.Size >= ID3v1TagLen then

begin

F.Position:= F.Size - ID3v1TagLen;
SetString(S, nil, 3);
F.ReadBuffer(S[1], 3);
end
else
S:= 'NON';
if S = 'TAG' then

F.Position:= F.Size - ID3v1TagLen
else
F.Position:= F.Size;
SaveTagToStream(F);
finally F.Free;
end;

end;

{ of procedure TID3v1Tag.SaveToFile }

procedure Tmp3Tag.SaveTagToStream(AStream: TStream);
var
Buf: array[0..ID3v1TagLen - 1] of Byte;
begin

SaveTag(Buf, ID3v1TagLen);
AStream.WriteBuffer(Buf, ID3v1TagLen);
end;

{ of procedure TID3v1Tag.SaveToStream }

procedure Tmp3Tag.SetCop(Value: string);
begin

Exit;
end;


procedure Tmp3Tag.SetField(AIdx: Integer;
S: string);
procedure SetIt(const ANewValue: string;
AMaxLen: Integer;
var AField: string);
begin

if Copy(ANewValue, 1, AMaxLen) <> AField then

begin

AField:= Copy(ANewValue, 1, AMaxLen);
fModified:= true;
end;

end;

begin

case AIdx of
1: SetIt(S, 30, FTitle);
2: SetIt(S, 30, fArtist);
3: SetIt(S, 4, fYear);
4: SetIt(S, 30, fAlbum);
5:
if fv1 then

SetIt(S, 30, fComment)
else

SetIt(S, 28, fComment);
end;

end;

{ of procedure TID3v1Tag.SetTitle }

procedure Tmp3Tag.SetGenre(const Value: string);
begin

if Value <> fGenre then

begin

fGenre:= Value;
fGenreID:= Genres.IndexOf(fGenre);
fModified:= true;
end;

end;


procedure Tmp3Tag.SetGenreID(AGenreID: Integer);
begin

if fGenreID <> AGenreID then

begin

fGenreID:= AGenreID;
fGenre:= Genres[fGenreID];
fModified:= true;
end;

end;

{ of procedure TID3v1Tag.SetGenreID}

procedure Tmp3Tag.SetID3Genres(const Value: TStringList);
begin

Exit;
// List should be read-only
end;


procedure Tmp3Tag.SetTrack(ATrack: Integer);
begin

if fTrack <> ATrack then

begin

fTrack:= ATrack;
fv1:= fTrack = 0;
fModified:= true;
end;

end;

{ of procedure TID3v1Tag.SetTrack }

procedure Tmp3Tag.Setv1(b: Boolean);
begin

if fv1 <> b then

begin

fv1:= b;
fModified:= true;
end;

end;

{ procedure TID3v1Tag.Setv1 }

end.