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• avcodec/hevcdec : Add pointers to logctx and parent ctx to HEVCLocalCtx

  29 juin 2022, par Andreas Rheinhardt

  avcodec/hevcdec : Add pointers to logctx and parent ctx to HEVCLocalCtx
  It is safe for a slice thread to read the main context
  
  and therefore it is safe to add a pointer to const HEVCContext
  
  (namely the parent context) to each HEVCLocalContext.
  
  It is also safe (and actually redundant) to add a pointer
  
  to a logcontext to HEVCLocalContext.
  Doing so allows to pass the HEVCLocalContext as context in
  
  the parts of the code that is run slice-threaded when slice-threading
  
  is in use (currently these parts of the code use ordinary
  
  HEVCContext*). This way one is not tempted to modify
  
  the main context from the slice contexts.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/hevcdec.c
  • [DH] libavcodec/hevcdec.h

• 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 ?

  


• avcodec/h264dec : Constify slices' pointer to the parent context

  24 mars 2022, par Andreas Rheinhardt

  avcodec/h264dec : Constify slices' pointer to the parent context
  Modifying the main context by a slice thread is racy ;
  
  so constify the pointer to it in H264SliceContext.
  
  The code itself was already compatible with this change.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/h264dec.h