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• C run linux shell command(fmpeg) 10x slower than typing directly in terminal

  14 November 2014, by dadylonglegs

  CLOSED

  I’m writing an application that execute a linux shell command (ffmpeg) from my C code. Such as:

  char command[2000];
  
  sprintf(command, "ffmpeg -i %s/%s -r 1 -vf scale=-1:120 -vframes 1 -ss  00:00:00 %s.gif", publicFolder, mediaFile, mediaFile);
  
  system(command);

  To extract video thumbnail from a specific video. But the strange that it is too much slower when executing shell command form C compare to typing directly to the terminal. I have no idea about this.
  Can anybody help me pls?. Thanks in advance.

• Why does ffmpeg command work in terminal but not subprocess.call

  4 August, by Brian

  I reviewed the "similar questions", but those seem to refer to using the full path for ffmpeg to ensure using the same version, which I am already doing so posting my question.

  


  I am using a Mac runnning Sequoia 15.5, python 3, and ffmpeg 4.2.1.

  


  I'm trying to write a script that can convert flac to mp3 320k.

  


  If I use the following command in terminal everything works as intended:

  


  /usr/local/bin/ffmpeg -i "/Volumes/MainData/Media/Media Server/_Stage/03 - People Like Us - Aaron Tippin.flac" -b:a 320k -map_metadata 0 -id3v2_version 3 "/Volumes/MainData/Media/Media Server/_Stage/03 - People Like Us - Aaron Tippin.mp3"


  


  But when trying to do the same thing with subprocess.call with the following:

  


  command = ['/usr/local/bin/ffmpeg', '-i', '/Volumes/MainData/Media/Media Server/_Stage/03 - People Like Us - Aaron Tippin.flac', '-b:a 320k', '-map_metadata 0', '-id3v2_version 3', '/Volumes/MainData/Media/Media Server/_Stage/03 - People Like Us - Aaron Tippin.mp3']
p = subprocess.call(command)


  


  I get this as a result:

  


  Unrecognized option 'id3v2_version 3'.
Error splitting the argument list: Option not found


  


  If I remove the '-id3v2_version 3', then the subprocess.call results in the following error:

  


  [mp3 @ 0x7fae2c008200] Invalid stream specifier: a 320k.


  


  Why does Terminal understand but subprocess.call doesn't when I've verified I'm using the same version of ffmpeg?

  


• Programmatically using terminal in linux escapes my command

  21 February 2023, by 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