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• Programmatically terminate ffmpeg child process on Raspberry Pi

  16 août 2020, par McGuireV10

  Is it possible to cleanly terminate ffmpeg when it's running as a child process under Linux (specifically on a Raspberry Pi 4B) ? I have a .NET Core 3.1 application which spawns ffmepg with the following command, which should encode an h.264 stream to an MP4 file :

  


  ffmpeg -framerate 24 -i - -b:v 2500k -c copy video.mp4


  


  After some arbitrary period of time I want to terminate ffmpeg, but everything I try is either ignored or causes ffmpeg to exit immediately — it never writes the MOOV chunk to the end of the MP4 file, which results in a corrupted file that cannot be played. I realize this chunk can take awhile to generate, and I've tried leaving the process alone for up to 60 seconds, which is far longer than h.264 to MP4 encoding requires interactively on the same device. For the record, I know how to create a "fragmented" MP4 which is mostly playable (using the -movflags switch and others), but I'm trying to generate a correct MP4.

  


  I've tried sending a Q key with or without various CR+LF combos, which I've seen mentioned in similar questions, but I think that's a Windows-only thing.

  


  I've tried every Unix signal as well as combinations of two signals. I saw somewhere (I think the ffmpeg site itself) that SIGINT should be sent twice, but that does nothing. In another SO post, somebody suggested sending SIGQUIT which also does nothing. Interestingly, sending SIGINT followed by SIGQUIT is the only combination that actually terminates the process, but it ends immediately with the following output :

  


  Error writing trailer of /media/ramdisk/video.mp4: Immediate exit requested
frame=  236 fps= 29 q=-1.0 Lsize=   28928kB time=00:00:09.79 bitrate=24201.9kbits/s speed= 1.2x
video:29167kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.


  


  I've tried a long delay between the two, nothing happens until the SIGQUIT at which point it responds as shown above. Oddly, sometimes it says received signal 3 instead of 2.

  


  There has to be some trick I'm missing.

  


• Use both stdio and stout in the same child process

  31 janvier 2021, par mr noob

  I am using ffmpeg to combine the audio/video 2 streams and pipe them to express. Here is my code :

  


  var ffmpeg = cp.spawn('ffmpeg', [
        // Set inputs
        '-i', 'pipe:4',
        '-i', 'pipe:5',
        // Map audio & video from streams
        '-map', '0:v',
        '-map', '1:a',
        // Keep encoding
        '-c', 'copy',
        '-movflags', 'frag_keyframe+empty_moov',
        '-f', 'mp4',
        // Define output file
        'pipe:1',
      ], {
        stdio: [
          /* Standard: stdin, stdout, stderr */
          'inherit', 'inherit', 'inherit',
          /* Custom: pipe:3, pipe:4, pipe:5 */
          'pipe', 'pipe', 'pipe',
        ],
      });
      video.pipe(ffmpeg.stdio[4]);
      audio.pipe(ffmpeg.stdio[5]);
      res.header('Content-Disposition', 'attachment; filename="video.mp4"');
      ffmpeg.stdout.pipe(res);


  


  But the code gives an error saying that ffmpeg.stout is null. After a bit of research, I found out that you can't have the stdio options array, or else stout will be null. Any way to fix this ?

  


• 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 !!!