JavaFX: Creando un front end para ffmpeg | Haciendo ScreenCast.

import java.io.File;
import javafx.application.Platform;
import javafx.concurrent.Task;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.AnchorPane;
import javafx.stage.DirectoryChooser;
import javafx.stage.Stage;
import javafx.stage.WindowEvent;
import utils.ScreenRecordUtils;

/**
 *
 * @author kalt
 */
public class Controller {

    @FXML
    private Button bRecord, bSaveTo;
    @FXML
    private AnchorPane anchorPane;
    private static String path = null;
    private Stage s;
   
    public Controller() {
        ScreenRecordUtils.sizeWindow();
    }

    @FXML
    protected void clicButtonRecord(MouseEvent e) {
        s = (Stage) anchorPane.getScene().getWindow();
        if (bRecord.getText().equals("Record")) {
            s.setIconified(true);
            bRecord.setText("Stop");
            bSaveTo.setDisable(true);
           
            Task t = new Task() {
                @Override
                protected Void call() {
                    ScreenRecordUtils.runCommand();
                    return null;
                }
            };
            new Thread(t).start();
           
            Platform.setImplicitExit(false);
            s.setOnCloseRequest((WindowEvent event) -> {
               
               if(s.getTitle().equals("Recording...")) {
                   event.consume();
                   Alert alert = new Alert(Alert.AlertType.WARNING);
                   alert.setTitle("Operacion no permitida: Gabracion en curso.");
                   alert.setHeaderText("La grabacion sigue en curso.");
                   alert.setContentText("Debe parar la grabacion en el boton de Stop.");
                   alert.showAndWait();
               } else {
                   Platform.exit();
               }
            });
            s.setTitle("Recording...");
        } else if (bRecord.getText().equals("Stop")) {
            ScreenRecordUtils.commandExit();
            bRecord.setText("Record");
            bRecord.setDisable(true);
            bSaveTo.setDisable(false);
            s.setTitle("My ScreenCast");
        }
    }

    @FXML
    protected void clicButtonSave(MouseEvent event) {
        DirectoryChooser dc = new DirectoryChooser();
        dc.setTitle("Guardar en...");
        File selectDirectory = dc.showDialog(s);
        if (selectDirectory != null && selectDirectory.isDirectory()) {
            File[] listFiles = selectDirectory.listFiles();
            path = selectDirectory.getAbsolutePath();
            for (File f : listFiles) {
                if (f.toString().equals(path + "/out.mkv")) {
                    f.delete();
                }
            }
            ScreenRecordUtils.modifyCommand(path);
            bRecord.setDisable(false);
        }
    }
}

    <?import java.lang.*?>
    <?import java.util.*?>
    <?import javafx.scene.control.*?>
    <?import javafx.scene.layout.*?>
    <?import javafx.scene.paint.*?>

    <AnchorPane fx:id="anchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="310.0" prefWidth="339.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/2.2" fx:controller="controller.Controller">
      <children>
        <Button fx:id="bSaveTo" layoutX="241.0" layoutY="268.0" mnemonicParsing="false" onMouseClicked="#clicButtonSave" text="Save to..." textAlignment="LEFT" textOverrun="CLIP" wrapText="false" />
        <Button fx:id="bRecord" disable="true" layoutX="111.0" layoutY="118.0" mnemonicParsing="false" onMouseClicked="#clicButtonRecord" text="Record" />
      </children>
    </AnchorPane>

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

/**
 *
 * @author kalt
 */
public class MainView extends Application {

    @Override
    public void start(Stage primaryStage) {
        configureUI(primaryStage);
    }

    private void configureUI(Stage s) {
        try {
            Parent root = FXMLLoader.load(getClass().getResource("/fxml/UI.fxml"));
            Scene scene = new Scene(root);
            scene.getStylesheets().add("/css/Style.css");
            s.setScene(scene);
            s.setResizable(false);

            s.centerOnScreen();
            s.setTitle("My ScreenCast");
            s.show();
        } catch (IOException ex) {
            Logger.getLogger(MainView.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

.button {
    -fx-padding: 10 10 15 15;
    -fx-background-insets: 0,0 0 5 0, 0 0 6 0, 0 0 7 0;
    -fx-background-radius: 8;
    -fx-background-color:  #00b300;        
    -fx-font-weight: bold;
    -fx-font-size: 2em;
    -fx-text-fill: white;
    -fx-text-alignment: center;
}
.button:hover {
    -fx-background-color: #cc0000;  
}
.button:pressed {
    -fx-padding: 10 15 13 15;
    -fx-background-insets: 2 0 0 0,2 0 3 0, 2 0 4 0, 2 0 5 0;
}

#bSaveTo {
    -fx-background-insets: 0,0 0 5 0, 0 0 6 0, 0 0 7 0;
    -fx-background-color:  #6666ff;  
    -fx-background-radius: 6;
    -fx-font-weight: bold;
    -fx-font-size: 0.85em;
    -fx-text-fill: white;
    -fx-text-alignment: center;
}

#bSaveTo:hover {
    -fx-background-color: #000099;
}
#bSaveTo:pressed {
    -fx-padding: 10 15 13 15;
    -fx-background-insets: 2 0 0 0,2 0 3 0, 2 0 4 0, 2 0 5 0;
 
}

import java.awt.Dimension;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import main.MainView;

/**
 *
 * @author kalt
 */
public class ScreenRecordUtils {

    private static String SIZE_WINDOW;
    private static String command = "ffmpeg -f alsa -ac 1 -i pulse -f x11grab -r 30 -s  -i :0.0 -acodec pcm_s16le -vcodec libx264 -preset ultrafast -crf 0 -threads 0 output";

    public static void sizeWindow() {
        Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        SIZE_WINDOW = screenSize.width + "x" + screenSize.height;
    }

    public static void modifyCommand(String path) {
        command = command.replace("-s", "-s " + SIZE_WINDOW);
        command = command.replace("output", path + "/out.mkv");
    }

    public static void runCommand() {
        try {
            commandExit();
            Process p = Runtime.getRuntime().exec(command);
            p.waitFor();
        } catch (IOException | InterruptedException ex) {
            Logger.getLogger(MainView.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static void commandExit() {
        try {
            Process p = Runtime.getRuntime().exec("pkill ffmpeg");
            p.waitFor();
        } catch (IOException | InterruptedException ex) {
            Logger.getLogger(MainView.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}