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• HTML5 Video FFMPEG Shell Script

  18 novembre 2011, par Schermy

  I wrote this quick and dirty shell script to run ffmpeg over a bunch of files to generate webm/ogg/h.264 videos for a HTML5 site.

  #!/bin/bash
  
  
  
  ext=$1
  
  enc=$2
  
  
  
  #!/bin/bash
  
  for file in *.$ext; do
  
          while pidof /usr/local/bin/ffmpeg; do sleep 10; done >/dev/null
  
  
  
          ffmpeg -i "$file" -s 1280x720 -b 500k  "${file/%$ext/$enc}"   
  
  done

  It works great for my purposes but I've noticed that each video now takes a lot longe to convert and ffmpeg is not taking advantage of my multi-core setup.

  I would like to improve this script when I have some time and make it available for use by others but I'd like to solve this issue first.

  Thanks in advance for all of your help.

  P.S. This is setup to use the ffmpeg installation from brew on the Mac (and yes I would like to make this script more platform agnostic later on).

• ffmpeg resize down larger video to fit desired size and add padding

  5 février 2017, par misterjinx

  I’m trying to resize a larger video to fit an area that I have. In order to achieve this I calculate first the dimensions of the resized video so That it fits my area, and then I try to add padding to this video so that the final result will have the desired dimension, keeping the aspect ratio as well.

  So let’s say that I have the original video dimensions of 1280x720 and to fit my area of 405x320 I need first to resize the video to 405x227. I do that. Everything is fine at this point. I do some math and I find out that I have to add 46 pixels of padding at the top and the bottom.

  So the padding parameter of the command for that would be -vf "pad=405:320:0:46:black". But each time I run the command I get an error like Input area 0:46:405:273 not within the padded area 0:0:404:226.

  The only docs for padding that I found is this http://ffmpeg.org/libavfilter.html#pad.

  I don’t know what I’m doing wrong. Anyone had this problem before ? Do you have any suggestions ?

• How to avoid a growing delay with ffmpeg between sound and raw video data ?

  13 novembre 2011, par roland

  Hello everybody and thank you for reading !

  Here is my problem : I have a program piping raw video frames to the standard output. This program is using OpenCV to capture and process the video and outputs directly the processed frames. The loop is synced to the framerate I chose. I'm using ffmpeg to read from the standard input and everything works fine for the video.
  But now that I added the sound I have a big problem : a growing delay is occuring and I really need to get rid of it. So here is my idea, but I really need your help :

  I have to find a way to include a timestamp information to the raw video. To be understandable by ffmpeg, it needs to be a known raw video compatible container. And then I will need to use the container API and pipe it to the standard output in my program. I really do not know what to use in the jungle of video formats and codecs, and I don't event know how to enable timestamp synchronizing in ffmpeg...

  If anyone has an idea, i am really interested here. For information, here is the command line i use to pipe the raw video :

  ./myprogram | ffmpeg -y -f alsa -i pulse -ac 2  -f rawvideo -vcodec rawvideo -r 24 -s 640x480 -pix_fmt bgr24 -i - -vcodec libx264 -pix_fmt yuv420p -r 24 -f flv -ar 44100 out.flv;

  Thand you very much,

  Roland