javacv error (Has setFormat() been called?)_ - opencv

Question

hi i'm making program that record video with audio by javacv but i got some error. any suggestion?
lib version : jdk 1.8 javacv 0.8 opencv 2.4.9
Exception in thread "main" org.bytedeco.javacv.FrameGrabber$Exception: avformat_open_input() error -2: Could not open input "output.mp4". (Has setFormat() been called?)
at org.bytedeco.javacv.FFmpegFrameGrabber.startUnsafe(FFmpegFrameGrabber.java:362)
at org.bytedeco.javacv.FFmpegFrameGrabber.start(FFmpegFrameGrabber.java:312)
at com.unomic.securobot.javacv.main(javacv.java:14)
my code
FFmpegFrameGrabber grabber1 = new FFmpegFrameGrabber("output.mp4");
FFmpegFrameGrabber grabber2 = new FFmpegFrameGrabber("test.mp3");
grabber1.setFormat("mp4");
grabber1.start();
grabber2.start();
FFmpegFrameRecorder recorder = new FFmpegFrameRecorder("outputFinal.mp4",
grabber1.getImageWidth(), grabber1.getImageHeight(),
grabber2.getAudioChannels());
recorder.setFrameRate(grabber1.getFrameRate());
recorder.setSampleFormat(grabber2.getSampleFormat());
recorder.setSampleRate(grabber2.getSampleRate());
recorder.start();
Frame frame1;
Frame frame2 = null;
while ((frame1 = grabber1.grabFrame()) != null ||
(frame2 = grabber2.grabFrame()) != null) {
recorder.record(frame1);
recorder.record(frame2);
}
recorder.stop();
grabber1.stop();
grabber2.stop();
}

Answer 1

I was trying to get thumbnails from a videos using the framegrabber. I was getting the same error but then I just tried giving the full path of the files and voila it worked. Previously, I was using a relative path which was not working. When I gave the full path it started working.
package com.tape.controller;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import javax.imageio.ImageIO;
import org.bytedeco.javacv.FFmpegFrameGrabber;
import org.bytedeco.javacv.OpenCVFrameGrabber;
public class VideoThumbTaker {
protected String ffmpegApp;
public VideoThumbTaker(String ffmpegApp)
{
this.ffmpegApp = ffmpegApp;
}
public void getThumb(String videoFilename, String thumbFilename, int width, int height,int hour, int min, float sec)
throws IOException, InterruptedException
{
ProcessBuilder processBuilder = new ProcessBuilder(ffmpegApp, "-y", "-i", videoFilename, "-vframes", "1",
"-ss", hour + ":" + min + ":" + sec, "-f", "mjpeg", "-s", width + "*" + height, "-an", thumbFilename);
Process process = processBuilder.start();
InputStream stderr = process.getErrorStream();
InputStreamReader isr = new InputStreamReader(stderr);
BufferedReader br = new BufferedReader(isr);
String line;
while ((line = br.readLine()) != null);
process.waitFor();
}
public static void main(String[] args) throws Exception, IOException
{
//Both case work
FFmpegFrameGrabber g = new FFmpegFrameGrabber("C:\\JavaEE\\New Project\\tape\\src\\main\\webapp\\web-resources\\videos\\vid.mp4");
g.setFormat("mp4");
g.start();
for (int i = 0 ; i < 50 ; i++) {
ImageIO.write(g.grab().getBufferedImage(), "png", new File("C:\\JavaEE\\New Project\\tape\\src\\main\\webapp\\web-resources\\thumbnails\\video-frame-" + System.currentTimeMillis() + ".png"));
}
g.stop();
}
}