MP3 reader - Practice Exercises Java

Lesson 8:

File management

Exercise 8.26:

MP3 reader

Objetive:

ID3 specifications apply to any file or audiovisual container. However, it is usually applied primarily audio containers. There are three versions of the specification that are compatible. For example, a file may contain labels simultaneously version 1.1 and version 2.0. In this case, the media player must decide which are relevant.

ID3 version 1
This first specification is very simple. It consists of attaching a fixed block size of 128 bytes at the end of the file in question. This block contains the following tags: A header that identifies the presence of block ID3 and version. Specifically, said header comprises TAG characters.

Title: 30 characters.
Artist: 30 characters.
Album: 30 characters.
Year: 4 characters.
Comment: 30 characters.
Genre (music): a character.

All tags using ASCII characters except gender, an integer stored within a single byte. The musical genre associated with each byte is predefined in the standard definitions and includes 80 genera, numbered 0 to 79. Some breeding programs have expanded their own defined genres (from 80th).

import java.util.*;
public class Main
{
	public static void main(String[] args)
	{
		final int SIZE = 128;

		byte[] data;

		System.out.print("Enter name: ");
		String name = new Scanner(System.in).nextLine();

		if (!(new java.io.File(name)).isFile())
		{
			System.out.println("Not exists");
			return;
		}

		try
		{
			java.io.FileInputStream file = File.OpenRead(name);

			data = new byte[SIZE];

			file.Seek(-128, SeekOrigin.End);
			file.read(data, 0, SIZE);

			file.close();

			byte b1 = data[0];
			byte b2 = data[1];
			byte b3 = data[2];

			if ((char)b1 != 'T' || (char)b2 != 'A' || (char)b3 != 'G')
			{
				System.out.println("not mp3 valid");
				return;
			}

			int i = 3;

			String title = "";
			for (; i < 33; i++)
			{
				if (data[i] != 0)
				{
					title += (char)data[i];
				}
			}

			String author = "";
			for (i = 33; i < 63; i++)
			{
				if (data[i] != 0)
				{
					author += (char)data[i];
				}
			}

			String album = "";
			for (i = 63; i < 93; i++)
			{
				if (data[i] != 0)
				{
					album += (char)data[i];
				}
			}

			String year = "";
			for (i = 93; i < 97; i++)
			{
				if (data[i] != 0)
				{
					year += (char)data[i];
				}
			}

			String comments = "";
			for (i = 97; i < 127; i++)
			{
				if (data[i] != 0)
				{
					comments += (char)data[i];
				}
			}

			System.out.println("Data of MP3:");
			System.out.println("----------------------------");
			System.out.println();

			System.out.println("Title: " + title);
			System.out.println("Author: " + author);
			System.out.println("Album: " + album);
			System.out.println("Year: " + year);
			System.out.println("Comments: " + comments);
			System.out.println("Genre: " + data[127]);
		}
		catch (RuntimeException e)
		{
			System.out.println("Error");
		}
	}
}