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• Python subprocess.Popen + ffmpeg breaks terminal input

  16 décembre 2020, par Barney Suit

  I was writing a module to create random screenshots from a video and used subprocess.Popen to run multiple commands in parallel but this leads to terminal refusing from showing any input once the python program is finished running. But it still accepts most inputs given from the keyboard it just doesn't display it.

  


  Only if I type the reset command terminal starts working fine
This happened on ssh with putty and other ssh clients even ssh with powershell on windows and directly running on terminal with VNC

  


  But without ssh directly running the same command on windows ssh works fine and and inputs are visible

  


  here's a gif example for whats happening


  


  and code to replicate it

  


  #!/usr/bin/env python3.8
from subprocess import Popen

def create_screenshots():

    commands = ['ffmpeg -hide_banner -loglevel panic -ss 329  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.329.frame.png"',
                'ffmpeg -hide_banner -loglevel panic -ss 312  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.312.frame.png"',
                'ffmpeg -hide_banner -loglevel panic -ss 533  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.533.frame.png"',
                'ffmpeg -hide_banner -loglevel panic -ss 444  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.444.frame.png"',
                'ffmpeg -hide_banner -loglevel panic -ss 411  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.411.frame.png"',
                'ffmpeg -hide_banner -loglevel panic -ss 413  -i "/home/user/file.mkv" -y -vframes 1   "/home/user/file.413.frame.png"']
    screenshot_files = []
    processes = [Popen(command, shell=True) for command in commands]
    for process in processes:
        process.wait()
    
    return screenshot_files


create_screenshots()


  


• Programmatically using terminal in linux escapes my command

  21 février 2023, par David Chavez

  Using nodeJS exec function which runs my command from a new process overwrites my backslashes which makes my command invalid. How can I prevent this or use a workaround ?

  


  I need the final command to look like this :
  
...drawtext=text='timestamp \: %{pts \: localtime...

  


  With that code, \: is escaped into :.
  
Using \\: is escaped into \\: while I'm expecting \:

  


  How do I get ...drawtext=text='timestamp \: %{pts \: localtime... to be ran ?

  


  // This command works if pasted directly into terminal
const ffmnpegCode = `ffmpeg -i /path/input.mp4 -y -r 25   -ss 0 -to 124 -c:v libx264 -c:a aac -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setsar=1,drawtext=text='timestamp \: %{pts \: localtime \: 1665679092.241 \: %m-%d-%Y %H\\\\\:%M\\\\\:%S}': x=(w-text_w-10): y=(h-text_h-5): fontsize=45: fontcolor=white@0.9: box=1: boxcolor=black@0.6: fontfile='/path/OpenSans-Regular.ttf'" /path/output.mp4`
const encode = async ffmpegCode => {
    try {
        await execPromise(ffmpegCode);
        return 200
    } catch (err) {
        console.log(err)
    }
}


  


  JS adds extra \ which breaks my command

  


• What does the variable ${i%.*} mean in terminal ?

  17 mars 2020, par wongz

  This shell command converts all .avi to .mp4 as per this answer by @llogan

  Can someone explain how $i%.* works ?
  In particular, what does % do ?

  for i in *.avi; do ffmpeg -i "$i" "${i%.*}.mp4"; done