running ffmpeg command in java Process hangs in waitFor()

Question

I'm running ffmpeg command to generate video for given images (img001.jpg, img002.jpg ...) it's creating slide.mp4, but it waits infinitely:

public class Ffmpeg {

public static void main(String[] args) throws IOException, InterruptedException {
    String path = "E:\\pics\\Santhosh\\FadeOut\\testing";       
    String cmd = "ffmpeg -r 1/5 -i img%03d.jpg -c:v libx264 -r 30 -y -pix_fmt yuv420p slide.mp4";
    runScript (path, cmd);
}

private static boolean runScript(String path, String cmd) throws IOException, InterruptedException {       
    List<String> commands = new ArrayList<String>();
    commands.add("cmd");
    commands.add("/c");
    commands.add(cmd);
    ProcessBuilder pb = new ProcessBuilder(commands);
    pb.directory(new File(path));
    pb.redirectErrorStream(true);
    Process process = pb.start();   
    flushInputStreamReader(process);                
    int exitCode = process.waitFor();
    return exitCode == 0;
}    
}

private static void flushInputStreamReader (Process process) throws IOException, InterruptedException {
            BufferedReader input = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String line=null;
            StringBuilder s = new StringBuilder();
            while((line=input.readLine()) != null) {            
                s.append(line);
            }
        }

Any suggestions?

After writing the function flushInputStreamReader, its working

If memory serves well, I think the problem is stuff in the InputStreamReader, u either have to read them out or disable it — nafas
– nafas, Commented Jun 9, 2015 at 10:11
btw, just do system.out.println("hello"); after runScript(path,cmd); — nafas
– nafas, Commented Jun 9, 2015 at 10:16
Hi @nafas after inserting system.out.println("hello"); its not working, how InputStreamReader related this ? — Mahesha M
– Mahesha M, Commented Jun 9, 2015 at 10:58
i believe the process waits, because technically program hasn't been finished . since there are still data to be read. so you can try to clear the stream (by reading it) and see if it works. as i said, I'm not 100% here as it was a while ago I had this problem — nafas
– nafas, Commented Jun 9, 2015 at 12:08

knucle · Accepted Answer · 2017-09-15 05:33:41Z

4

Aside from reading the ErrorStream, there's a better way to handle this.

Add -loglevel quiet to the command, so that the ErrorStream won't overflow and blocking the process at the first place.

answered Sep 15, 2017 at 5:33

knucle

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Adrian Mole · Accepted Answer · 2021-02-14 13:12:49Z

Here the working code for the live project:

public void executeHLS() throws IOException, InterruptedException {
        String original_video_file = "C:\\xampp\\htdocs\\hls\\test.mp4";
        String conversion = "cmd.exe /c F:\\java\\ffmpeg\\ffmpeg\\bin\\ffmpeg -i "+original_video_file+" -hls_time 10  -hls_playlist_type vod -hls_segment_filename \"C:\\xampp\\htdocs\\hls\\video_segments_%0d.ts\" C:\\xampp\\htdocs\\hls\\hls_master_for_test.m3u8";
        //String conversion = "cmd.exe /c "+"dir";
        String[] cmds={conversion};
        
        for(int i=0;i<cmds.length;i++) {
             try {
                System.out.println(cmds[i]);
                if(runScript(conversion)) {
                    System.out.println("Operation Successfull!!!!");
                }else {
                    System.out.println("Operation Failed ####");
                }
             } catch (IOException e) {
                 e.printStackTrace();
             }
             //System.exit(0);
            
         }
    }
    private static boolean runScript(String cmd) throws IOException, InterruptedException {       
        ArrayList<String> commands = new ArrayList<String>();
        commands.add("cmd");
        commands.add("/c");
        commands.add(cmd);
        ProcessBuilder pb = new ProcessBuilder(commands);
        //pb.directory(new File(path));
        pb.redirectErrorStream(true);
        Process process = pb.start();   
        flushInputStreamReader(process);                
        int exitCode = process.waitFor();
        return exitCode == 0;
    }    
    
    private static void flushInputStreamReader (Process process) throws IOException, InterruptedException {
            BufferedReader input = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String line=null;
            StringBuilder s = new StringBuilder();
            while((line=input.readLine()) != null) {            
                s.append(line);
            }
    }

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