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• A 'clean' way to cut an MP4 movie into two sections using FFMPEG ?

  30 août 2020, par Peter in Japan

  I am attempting to use FFMPEG to make a script that can easily split a short MP4 movie with sound into two pieces at a certain point. I've searched through what feels like hundreds of posts to try to find "the" answer, but most of my attempts end up with poor results, broken video files that cause my video play to freeze, and so on. I am attempting to make a script that allows me to easily cut a short anime movie (something grabbed from Twitter or some other short source) and cut it into two sections, so it can be under the 2:20 Twitter time limit, or to cut out some scene I don't want to show my followers.

  


  The issue is that FFMPEG is good at cutting videos into segments, but bad at know where keyframes are, so most videos have two seconds of blank video at the front before some keyframe appears, which looks terrible.

  


  One example I found that works well is below, which cuts any mp4 into a bunch of chunks of n second size (six seconds in the example below). Source and documentation for this is https://moe.vg/3b8eNTs

  


  ffmpeg -i seitokai.mp4 -c:v libx264 -crf 22 -map 0 -segment_time 6 -reset_timestamps 1 -g 30 -sc_threshold 0 -force_key_frames "expr:gte(t,n_forced*1)" -f segment output%03d.mp4

  


  This code works great, at least allowing me to access the "left" side of a video that I want, in this case a six-second segment I want. Can anyone tell me how to accomplish the above, but starting at the 13-second period in said video, so I could get right "right" (not starting from 00:00:00) video cut cleanly ?

  


  Alternately, a single, unified and elegant way to split (re-encode) an MP4 into two segments that forces keyframes from the very beginning of the cut pieces would be wonderful. I can't believe how hard this seems to be.

  


  Thanks in advance for any help you can give ! Greetings from rural Japan !

  


• How to make shell exec run in background while php continues

  30 juin 2015, par Jizbo Jonez

  I have ffmpeg doing a video conversion in a PHP file and it works as it should. The problem is it takes up to a minute for this to finish. I thought it might be easy to do but I can only get it to work in the background when I use just one command (eg single pass conversion without mp4box) like this

  exec("nohup " . $ffmpegPath . " -i " . $srcFile . " -f mp4 -vcodec libx264 -crf 27 -s " . $srcWidth . "x" . $srcHeight . " -an -r 20 " . $destFile . ".mp4 > /dev/null 2>&1 &");

  The problem is I need to use three different commands to do a proper conversion though. So far my commands look like this in the PHP file and it works, but with a massive delay :

  exec($ffmpegPath . " -y -i " . $srcFile . " -f mp4 -pass 1 -passlogfile " . $video_pass_log . " -vcodec libx264 -vpre ipod640 -b:v 2M -bt 4M -an " . $destFile . ".mp4");
  
  exec($ffmpegPath . " -y -i " . $srcFile . " -f mp4 -pass 2 -passlogfile " . $video_pass_log . " -vcodec libx264 -vpre ipod640 -b:v 2M -bt 4M -acodec libfaac -ac 2 -ar 44100 -ab 96k " . $destFile . ".mp4");
  
  exec($mp4boxpath . " -tmp /tmp -hint " . $destFile . ".mp4");

  How can I make the shell exec run in background while PHP continues ?

• ffmpeg - create from .png - [on hold]

  9 janvier 2016, par John

  I am new user to R studio.
  I want to create a video from a serie of .png files.
  I have checked the post about doing so but using the code provided result in error. I get the " unexpected token " error with command like :
  ffmpeg -r 1/5 ...etc
  says " unexpected token 1 " ; ..then a bunch of other unexpected token...
  What is wrong with the command line ? Do I need to install a package to use this ffmpeg ? If so, using the command " install.ffmpeg or install.package() didn’t work.
  Any help on this ? thanks !