Extract song information from MP3
In addition to music information, a MP3 song contains information such as song name, singer and so on, when we listen to music with Winamp software, the playlist automatically reads the information. Most people like downloading music from the Internet, but download the MP3 file name is the file upload system automatically named, and the song itself simply does not match, so, to the user brought a lot of trouble. However, lazy people have the practice of lazy people, why don't we write a program, the song information automatically read out and automatically renamed for MP3 files?
Below I will use C # as a tool to write out the development process.
The extra information for a MP3 is held at the end of the file, representing a total of 128 bytes, including the following (we define a structure description):
public struct Mp3info
{
public string Identify;//tag, three bytes
public string title;//song name, 30 bytes
public string artist;//singer name, 30 bytes
public string album;//belongs to record, 30 bytes
public string year;//year, 4 characters
public string comment;//Comment, 28 bytes
Public char reserved1;//reserved bit, one byte
Public char reserved2;//reserved bit, one byte
Public char reserved3;//reserved bit, one byte
}
So, we can just read the last 128 bytes of the MP3 file and save it in the structure. The function is defined as follows:
<summary>
Get the last 128 bytes of the MP3 file
</summary>
<param name= "filename" > FileName </param>
<returns> return byte array </returns>
Private byte[] getLast128 (string FileName)
{
FileStream fs = new FileStream (filename,filemode.open,fileaccess.read);
Stream stream = FS;
Stream. Seek ( -128,seekorigin.end);
const int SEEKPOS = 128;
int RL = 0;
byte[] Info = new Byte[seekpos];
RL = stream. Read (Info,0,seekpos);
Fs. Close ();
Stream. Close ();
return Info;
}
The byte array returned above is then segmented and saved into the MP3INFO structure for return.
<summary>
Get information on MP3 songs
</summary>
<param name = "Info" > binary information intercepted from MP3 file </param>
<returns> return to a MP3INFO structure </returns>
Private Mp3info Getmp3info (byte[] Info)
{
Mp3info mp3info = new Mp3info ();
string str = NULL;
int i;
int position = start value of 0;//loop
int currentindex = Current index value of 0;//info
Get tag ID
for (i = currentindex;i<currentindex+3;i++)
{
str = str+ (char) info[i];
position++;
}
Currentindex = position;
mp3info.identify = str;
Get the name of the song
str = NULL;
byte[] Byttitle = new byte[30];//reads the song name part into a separate array
int j = 0;
for (i = currentindex;i<currentindex+30;i++)
{
BYTTITLE[J] = Info[i];
position++;
j + +;
}
Currentindex = position;
Mp3info.title = this.bytetostring (Byttitle);
Get the name of the singer
str = NULL;
j = 0;
byte[] Bytartist = new byte[30];//reads the singer name part into a separate array
for (i = currentindex;i<currentindex+30;i++)
{
BYTARTIST[J] = Info[i];
position++;
j + +;
}
Currentindex = position;
Mp3info.artist = this.bytetostring (bytartist);
Get album name
str = NULL;
j = 0;
byte[] Bytalbum = new byte[30];//reads part of the album name into a separate array
for (i = currentindex;i<currentindex+30;i++)
{
BYTALBUM[J] = Info[i];
position++;
j + +;
}
Currentindex = position;
Mp3info.album = this.bytetostring (bytalbum);
Get year
str = NULL;
j = 0;
byte[] Bytyear = new byte[4];//reads the year part into a separate array
for (i = currentindex;i<currentindex+4;i++)
{
BYTYEAR[J] = Info[i];
position++;
j + +;
}
Currentindex = position;
Mp3info.year = this.bytetostring (bytyear);
Get comments
str = NULL;
j = 0;
byte[] Bytcomment = new byte[28];//reads the annotation section into a separate array
for (i = currentindex;i<currentindex+25;i++)
{
BYTCOMMENT[J] = Info[i];
position++;
j + +;
}
Currentindex = position;
Mp3info.comment = this.bytetostring (bytcomment);
The following gets the reserved bit
mp3info.reserved1 = (char) info[++position];
Mp3info.reserved2 = (char) info[++position];
Mp3info.reserved3 = (char) info[++position];
return mp3info;
}
The above procedure uses the following method:
<summary>
Converts a byte array to a string
</summary>
<param name = "B" > byte array </param>
<returns> returns the converted string </returns>
private string bytetostring (byte[] b)
{
Encoding enc = encoding.getencoding ("GB2312");
String str = Enc. GetString (b);
str = str. Substring (0,str. IndexOf (' >= ') 0? Str. IndexOf (' the '): Str. LENGTH);//Remove unwanted characters
return str;
}
What about renaming? We renamed the song according to the name of the song (singer), and the procedure was as follows:
<summary>
Change file name
</summary>
<param name= "FilePath" > FileName </param>
<returns></returns>
private bool ReName (string FilePath)
{
if (file.exists (FilePath))
{
Mp3info mp3info = new Mp3info ();
Mp3info = This.getmp3info (this.getlast128 (FilePath));/read out file information
Mp3info.artist = this. Deletenotvalue (mp3info.artist);
Mp3info.title = this. Deletenotvalue (Mp3info.title);
if (Mp3Info.Artist.Trim (). length==0)
{
Mp3info.artist= "not named";
}
if (Mp3Info.Title.Trim (). length==0)
{
Mp3info.title= "not well-known song";
}
Try
{
Renamed
File.move (filepath,filepath.substring) (0,filepath.tolower (). LastIndexOf ("\")). Trim () + "\" + "(" + mp3Info.Artist.Trim () + ")" +mp3info.title.trim () + ". mp3");
return true;
}
catch (Exception)
{
return false;
}
}
Else
{
return false;
}
}
Ah, the idea is this, if there is a problem or need source code, please send an email to: lifenote@21cn.com request.
