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• Kill child process only after readFile() Node js Electron

  14 mai 2021, par Radespy

  I'm using an imported ffmpeg binary ffmpeg-static-electronin an Electron-React app (on Windows Pro 10) and want to delete a saved cropped video and then kill the child process afterwards from my Main process.

  


  The overall aim is to crop a video of the whole screen following capture and then send the cropped video to a renderer.

  


  const fsPromises = require('fs').promises
const ffmpeg = require('ffmpeg-static-electron')
const { execFile } = require("child_process")


ipcMain.on("windoze_capture_screen:video_buffer", async (event, buffer) => {
    const temp_directory =  await fsPromises.mkdtemp(await fsPromises.realpath(os.tmpdir()) + path.sep)
    const capture_screen_video_path = path.join(temp_directory, "screen_capture_video.mp4")

    child_object = execFile(`${ffmpeg.path}`, 

            ['-i', `${capture_screen_video_path}`, '-vf', `crop=${width}:${height}:${x_pos}:${y_pos}`, `${path.join(temp_directory,'cropped_video.mp4')}`])
            
    child_object.on("exit", async () => {

        // child_object.kill()
        console.log("?Killed -1", child_object.killed)
        
        try { 
            databasePayload.video_buffer = await fsPromises.readFile(path.join(temp_directory, "cropped_video.mp4"), {encoding: 'base64'})
            mainWindow.webContents.send("main_process:video_buffer", databasePayload.video_buffer)
        } catch (error) {
            console.log(error)
        } finally {

            // child_object.kill()
            console.log("?Killed - 2", child_object.killed)
            
            // noASAR required to be set to 'true' in order to remove temp directory in build
            process.noAsar = true 
            fs.rmdir(temp_directory, {recursive: true}, (error) => {if (error) {log(error)}})
            process.noASAR = false
            }

            // 3rd scenario
            // child_object.kill()
            console.log("?Killed -3", child_object.killed)   
        })

        // 4th scenario
        console.log("?Killed-4", child_object.killed)   
    })



  


  When running each of these scenarios, I get the following outputs.

  


  Scenario's 1, 2 and 3 - Successfully sends cropped video to renderer but doesn't kill process.

  


  Output :

  


  ?Killed-4 false
?Killed -1 false
[ffmpeg version 3.0.1 Copyright (c) 2000-2016 the FFmpeg developers built with gcc 5.3.0 (GCC).... etc. ]
?Killed-2 false
?Killed -3 false


  


  Scenario 4 - Doesn't crop video

  


  ?Killed-4 true
?Killed -1 true
Command failed: C:\Users\XXX\Desktop\windows-electron-forge\node_modules\ffmpeg-static-electron\bin\win\x64\ffmpeg.exe -i C:\Users\XXX\AppData\Local\Temp\4WgnUw\screen_capture_video.mp4 -vf crop=796:763:462:509 C:\Users\XXX\AppData\Local\Temp\4WgnUw\cropped_video.mp4

[Error: ENOENT: no such file or directory, open 'C:\Users\XXX\AppData\Local\Temp\4WgnUw\cropped_video.mp4'] {
errno: -4058,
code: 'ENOENT',
syscall: 'open',
path: 'C:\\Users\\XXX\\AppData\\Local\\Temp\\4WgnUw\\cropped_video.mp4'
}
?Killed - 2 true
?Killed -3 true


  


  The last scenario has been tried out of desperation.

  


  Question : Where am I going wrong with this ? I suspect it's something to do with ipc between child and parent process but not sure where to place the code.

  


  Any help will be much appreciated !!!

  


• Revert "avformat/hls : copy rw_timeout from parent to child AVIOContexts."

  17 avril 2018, par Steven Liu

  Revert "avformat/hls : copy rw_timeout from parent to child AVIOContexts."
  This reverts commit 36deec010cc87c8990477e1703dbf785212992b5.
  

  • [DH] libavformat/hls.c

• how to get the output of a child process in a variable c#

  4 août 2022, par Dokoa

  I want to get width, height information into a variable after ffprobe is finished.

  


  int width, height;   
Process pr = new Process();
                pr.StartInfo.FileName = "ffprobe";
                pr.StartInfo.Arguments = $"- v error - select_streams v: 0 - show_entries stream = width,height - of default = nw = 1 input.mp4";
                pr.StartInfo.UseShellExecute = false;
                pr.StartInfo.CreateNoWindow = true;
                pr.EnableRaisingEvents = true;
                pr.Start();


  


  example of ffprobe console output

  


  width=320
height=180