New Mash

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import javax.swing.JOptionPane;
import javax.swing.JTextField;


/**
 * Francis Lyons
 * 10/13/14
 *
 *   program built to delete i frames and repeat certain sections of b-frames
 *
 *   takes as an argument the filename w/o filetype of the video to be used (works with videos in AVI format, converted using FFMPEG)
 *
 *   reccomended to use avidemux or something similar to find total number of frames in video / specific frame locations
 */

public class NewMash
{
	public static final int[] F_BYTES = new int[4];
	public static final int[] I_BYTES = new int[4];

	/*
	 * the nextFrame method should return the long position of the
	 * beginning of the next frame, regardless of if it is a keyframe
	 * or not.  method will return -1 if it hits the end of the file
	 * before finding another frame
	 * takes as a parameter the current read position in the file
	 */
	public static long nextFrame(RandomAccessFile file, long start) throws IOException
	{
		long startPos = -1;
		long currentPos = start;  // get current read position
		file.seek(start);

		while(file.getFilePointer() < file.length())
		{
			file.seek(currentPos);  // currentPos is incremented by 1 each time, reads in if went to far
			if(file.read() == F_BYTES[0] && file.read() == F_BYTES[1] && file.read() == F_BYTES[2] && file.read() == F_BYTES[3])
			{
				// we have found the beginning of a frame
				// grab the found frame start position and get out of the while loop

				startPos = currentPos;
				break;
			}
	    	currentPos++;
		}
		file.seek(start);
		return startPos;
	}


	/*
	 * method to check if current frame is a keyframe
	 * to be used properly this method should be used in conjunction
	 * with nextFrame (this method should take as a parameter the long position
	 * of the beginning of a frame in the file, then it will return boolean
	 * of whether or not the frame is an i frame)
	 *
	 * right now the number of bytes to search for the iframe flag
	 * is hardcoded at 15 to be safe
	 */
	public static boolean isIFrame(RandomAccessFile file, long pos) throws IOException
	{
	    boolean iFrame = false;

	    for(int i = 0; i < 15; i++)
	    {
			file.seek(pos + i);  // start reading at the given position, then moves 1 forward each time

			if(file.read() == I_BYTES[0] && file.read() == I_BYTES[1] && file.read() == I_BYTES[2] && file.read() == I_BYTES[3])
			{
				// we have found the flag that indicates that this is an iframe
				// exit the for loop

				iFrame = true;
				break;
			}
	    }
	    file.seek(pos);
	    return iFrame;
	}


	public static void main(String[] args) throws IOException
	{

		String filename = args[0];  // only argument should be the filename of the video

		// get user input for various parameters
		JTextField endBeginTxtFld = new JTextField(); // end of beginning unchanged area
		JTextField startTxtFld = new JTextField(); // start of changed area
		JTextField endTxtFld = new JTextField();  // end of changed area
		JTextField repeatTxtFld = new JTextField(); // number of times to repeat each frame
		JTextField totalRepTxtFld = new JTextField();  //  number of times to repeat whole change area

		Object[] message = {"end of beginning: ", endBeginTxtFld,
						"start frame: ", startTxtFld,
						"end frame: ", endTxtFld,
						"number of times to repeat each frame: ", repeatTxtFld,
						"number of times to repeat total frame area: ", totalRepTxtFld};

		JOptionPane.showConfirmDialog(null, message, "Enter Specified Values", JOptionPane.OK_OPTION);

		// get strings for each of the inputs
		String endBegStr = endBeginTxtFld.getText();
		String startStr = startTxtFld.getText();
		String endStr = endTxtFld.getText();
		String repeatStr = repeatTxtFld.getText();
		String totalRepStr = totalRepTxtFld.getText();

		// get usable integer values from above strings
		int endBegin = Integer.parseInt(endBegStr);
		int start = Integer.parseInt(startStr);
		int end = Integer.parseInt(endStr);
		int repeat = Integer.parseInt(repeatStr);
		int totalRep = Integer.parseInt(totalRepStr);


		F_BYTES[0] = 48; // decimal equivalent of 30 in hex
		F_BYTES[1] = 48; // decimal equivalent of 30 in hex
		F_BYTES[2] = 100; // decimal equivalent of 64 in hex
		F_BYTES[3] = 99; // decimal equivalent of 63 in hex

		I_BYTES[0] = 0; // decimal equivalent of 00 in hex
		I_BYTES[1] = 1; // decimal equivalent of 01 in hex
		I_BYTES[2] = 176; // decimal equivalent of B0 in hex
		I_BYTES[3] = 1; // decimal equivalent of 01 in hex


		RandomAccessFile file = new RandomAccessFile(filename + ".avi", "rw");

		// skip some initial frames otherwise video just changes from green
		int frames = 0;
		long current = nextFrame(file, 0);
		System.out.println("finding beginning");
		while(frames < endBegin)
		{
			current = nextFrame(file, current + 1);
			frames++;  // found another frame, increment count
			//System.out.println(frames + " / " + copyBegin);
		}


	    FileOutputStream newFile = new FileOutputStream(filename + "_0.avi" ,true);

		file.seek(0);
	    System.out.println("copying beginning");
	    // copy beginning of file until moved past startOffSet number of frames
		while(file.getFilePointer() < current)
		{
		   newFile.write(file.readByte());
		}

		System.out.println("skipping from beginning to repeat area");

		// go through these frames but dont read them over
		while(frames < start)
		{
			current = nextFrame(file, current + 1);
			frames++;  // found another frame, increment count
			//System.out.println(frames + " / " + start);
		}


    	long currFrame = nextFrame(file, file.getFilePointer());
    	long nextFrame;

    	long startFrame = currFrame;

	    // need to loop through file and copy over bytes unless we are in an iframe
    	System.out.println("copying repeat area");
    	for(int j = 0; j < totalRep; j++)
    	{
    		file.seek(startFrame);
    		currFrame = startFrame;
    		nextFrame = nextFrame(file, currFrame + 1);
        	int frameCount = start;

		    while(file.getFilePointer() < file.length() && frameCount < end)
		    {
		    	if(nextFrame == -1)
		    	{
		    		// there is no next frame, just copy the rest
		    	    while(file.getFilePointer() < file.length())
		    	    {
		    	    	newFile.write(file.readByte());
		    	    }
		    	}

		    	// if next frame is iFrame and we want to delete them, skip past it
		    	else if(isIFrame(file, currFrame))
		    	{
		    		//System.out.println("skipped iFrame");
		    		// skip to next frame
		    		file.seek(nextFrame);
		    	}

		    	// if not iFrame then we want to copy it
		    	else
		    	{
				    for(int i = 0; i < repeat; i++)
				    {
				   		while(file.getFilePointer() < nextFrame)
				   		{
				   			newFile.write(file.readByte());
				   		}
				   		file.seek(currFrame);
				   	}
		    	}

		    	// nextFrame is now the current frame
		    	currFrame = nextFrame;
		    	nextFrame = nextFrame(file, file.getFilePointer() + 1);
		    	frameCount++;
		    	//System.out.println(frameCount + " / " + end);
		    	newFile.flush();
		    	//System.out.println(file.getFilePointer() + " / " + file.length());
		    }
		    System.out.println("repeat: " + j);
    	}

    	System.out.println("copying end");
	    while(file.getFilePointer() < file.length())
	    {
		    //copy rest of the file after 'end'
	    	nextFrame = nextFrame(file, file.getFilePointer() + 1);

	    	if(nextFrame == -1)
	    	{
	    		// there is no next frame, just copy the rest
	    	    while(file.getFilePointer() < file.length())
	    	    {
	    	    	newFile.write(file.readByte());
	    	    }
	    	}

	    	// if next frame is iFrame and we want to delete them, skip past it
	    	else if(isIFrame(file, currFrame))
	    	{
	    		//System.out.println("skipped iFrame");
	    		// skip to next frame
	    		file.seek(nextFrame);
	    	}

	    	// if not iFrame or we want to keep iFrames then copy it
	    	else
	    	{
			    while(file.getFilePointer() < nextFrame)
			    {
			    	newFile.write(file.readByte());
			    }
			    file.seek(currFrame);
	    	}
	    	currFrame = nextFrame;
	    	nextFrame = nextFrame(file, file.getFilePointer() + 1);
	    	newFile.flush();
	    }

	    System.out.println("done");
	    newFile.close();
	}

}