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• Killing a Python process from Node doesn't kill Python's child process (child process being ffmpeg.exe)

  3 avril 2022, par Impasse

  I am developing an Electron application. In this application, I am spawning a Python process with a file's path as an argument, and the file itself is then passed to ffmpeg (through the ffmpeg-python module) and then goes through some Tensorflow functions.

  


  I am trying to handle the case in which the user closes the Electron app while the whole background process is going. From my tests though, it seems like ffmpeg's process stays up no matter what. I'm on Windows and I'm looking at the task manager and I'm not sure what's going on : when closing the Electron app's window, sometimes ffmpeg.exe will be a single process, some other times it will stay in an Electron processes group.

  


  I have noticed that if I kill Electron's process through closing the window, the python process will also close once ffmpeg has done its work, so I guess this is half-working. The problem is, ffmpeg is doing intensive stuff and if the user needs to close the window, then the ffmpeg process also NEEDS to be killed. But I can't achieve that in any way.

  


  I have tried a couple things, so I'll paste some code :

  


  main.js

  


  // retrieve video data
ipcMain.handle('get-games', async (event, arg) => {
    const spawn = require('child_process').spawn;
    const pythonProcess = spawn('python', ["./backend/predict_games.py", arg]);

    // sets pythonProcess as a global variable to be accessed when quitting the app
    global.childProcess = pythonProcess;

    return new Promise((resolve, reject) => {
        let result = "";

        pythonProcess.stdout.on('data', async (data) => {
            data = String(data);

            if (data.startsWith("{"))
                result = JSON.parse(data);
        });

        pythonProcess.on('close', () => {
            resolve(result);
        })

        pythonProcess.on('error', (err) => {
            reject(err);
        });
    })
});

app.on('before-quit', function () {
    global.childProcess.kill('SIGINT');
});


  


  predict_games.py (the ffmpeg part)

  


  def convert_video_to_frames(fps, input_file):
    # a few useful directories
    local_dir = os.path.dirname(os.path.abspath(__file__))
    snapshots_dir = fr"{local_dir}/snapshots/{input_file.stem}"

    # creates snapshots folder if it doesn't exist
    Path(snapshots_dir).mkdir(parents=True, exist_ok=True)

print(f"Processing: {Path(fr'{input_file}')}")
try:
    (
        ffmpeg.input(Path(input_file))
        .filter("fps", fps=fps)
        .output(f"{snapshots_dir}/%d.jpg", s="426x240", start_number=0)
        .run(capture_stdout=True, capture_stderr=True)
    )
except ffmpeg.Error as e:
    print("stdout:", e.stdout.decode("utf8"))
    print("stderr:", e.stderr.decode("utf8"))


  


  Does anyone have any clue ?

  


• Flutter ffmpeg_kit_flutter : get FFmpegKit.executeAsync error

  2 août 2022, par Pitu Werno

  I have prepared a test program to run FFMPEG command and it successfully run -i "/data/user/0/com.example.test/cache/file_picker/test.mp4" -c:v mpeg4 "/data/user/0/com.example.test/cache/test-1639310478143.mp4" command. This is just to ensure that ffmpeg_kit_flutter was loaded properly and all permissions has been obtained.

  


  But, I have problem executing -i "source.mp4" -vf fps=30 "thumb%03d.jpg" -hide_banner command. The command itself is working well when I run it on windows, for example :

  


  md frame1
ffmpeg -i "test.mp4" -vf fps=30 frame1/thumb%%04d.jpg -hide_banner


  


  (note : double % is to escape the % in windows batch file)

  


  This is what I do in flutter on android :

  


  

  1. Create temporary folder.

  


  2. Execute :

  


  


      String command = '-i "/data/user/0/com.example.test/cache/file_picker/test.mp4" -vf fps=30 "/data/user/0/com.example.test/cache/tmp-1639309602536/thumb%03d.jpg" -hide_banner';
    FFmpegKit.executeAsync(command, (session) async {
        final returnCode = await session.getReturnCode();
        if (ReturnCode.isSuccess(returnCode)) {
            //ok
        } else if (ReturnCode.isCancel(returnCode)) {
            //cancelled
        } else {
            //error
        }
    });


  


  The proses is not working (always going to the error part). My questions are :

  


  

  1. What is the difference between running that command on windows and android ? Why it works on windows but not working on android ?

  


  2. How can I get the explanation about any FFMPEG error ? In my case, I only know that wasn't working, but I have no clue why.

  


  


• A process' child doesn't get killed from killing the parent process

  2 avril 2022, par Impasse

  I am developing an Electron application. In this application, I am spawning a Python process with a file's path as an argument, and the file itself is then passed to ffmpeg (through the ffmpeg-python module) and then goes through some Tensorflow functions.

  


  I am trying to handle the case in which the user closes the Electron app while the whole background process is going. From my tests though, it seems like ffmpeg's process stays up no matter what. I'm on Windows and I'm looking at the task manager and I'm not sure what's going on : when closing the Electron app's window, sometimes ffmpeg.exe will be a single process, some other times it will stay in an Electron processes group.

  


  I have noticed that if I kill Electron's process through closing the window, the python process will also close once ffmpeg has done its work, so I guess this is half-working. The problem is, ffmpeg is doing intensive stuff and if the user needs to close the window, then the ffmpeg process also NEEDS to be killed. But I can't achieve that in any way.

  


  I have tried a couple things, so I'll paste some code :

  


  main.js

  


  // retrieve video data
ipcMain.handle('get-games', async (event, arg) => {
    const spawn = require('child_process').spawn;
    const pythonProcess = spawn('python', ["./backend/predict_games.py", arg]);

    // sets pythonProcess as a global variable to be accessed when quitting the app
    global.childProcess = pythonProcess;

    return new Promise((resolve, reject) => {
        let result = "";

        pythonProcess.stdout.on('data', async (data) => {
            data = String(data);

            if (data.startsWith("{"))
                result = JSON.parse(data);
        });

        pythonProcess.on('close', () => {
            resolve(result);
        })

        pythonProcess.on('error', (err) => {
            reject(err);
        });
    })
});

app.on('before-quit', function () {
    global.childProcess.kill('SIGINT');
});


  


  predict_games.py (the ffmpeg part)

  


  def convert_video_to_frames(fps, input_file):
    # a few useful directories
    local_dir = os.path.dirname(os.path.abspath(__file__))
    snapshots_dir = fr"{local_dir}/snapshots/{input_file.stem}"

    # creates snapshots folder if it doesn't exist
    Path(snapshots_dir).mkdir(parents=True, exist_ok=True)

print(f"Processing: {Path(fr'{input_file}')}")
try:
    (
        ffmpeg.input(Path(input_file))
        .filter("fps", fps=fps)
        .output(f"{snapshots_dir}/%d.jpg", s="426x240", start_number=0)
        .run(capture_stdout=True, capture_stderr=True)
    )
except ffmpeg.Error as e:
    print("stdout:", e.stdout.decode("utf8"))
    print("stderr:", e.stderr.decode("utf8"))


  


  Does anyone have any clue ?