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• Using ffmpeg codec inside Xamarin ?

  6 juin 2016, par Ahmed Mujtaba

  I’ve been struggling with this topic for the past few weeks and I am yet to find a way to use ffmpeg inside my Xamarin project. There are couple of C# wrappers that work great but they don’t work for API 15 and below versions of Android.

  I’m trying to use ffmpeg in my project but I really don’t know how to. I have tried to bind a Java project I found but .jar binding didn’t work and apparently the only way is to use JNI for the binding which isn’t very easy to do, at least for me.

  I’m hoping someone can provide me some sources I can read on and understand how it works and what ways I can use ffmpeg in my project.

  I will really appreciate any kind of help I can get.

• Merging Many Webms With FFMPEG

  10 août 2016, par cfog

  We’ve been trying to merge multiple webms together so that they play in series in a new webm using FFMPEG. These webms are from multiple sources (webcams), so the resolution will vary.

  We’re using these options, it works perfectly for 3 files. But, we need to be able to do it for n number video files.

  -filter_complex "[1:v]scale=640:-1[v1]; [0:v][0:a][v1][1:a][2:v]
  
  [2:a]concat=n=3:v=1:a=1[v][a]" -map "[v]" -map "[a]"

• How to use the function expr in drawtext ffmpeg to add a text to video ?

  18 décembre 2013, par nhanpt

  I'm try to add a text to my video using FFmpeg.
  Sources : http://www.ffmpeg.org/ffmpeg-all.html#drawtext-1

  ffmpeg -i 1385363109.avi -vf "drawtext=fontfile=/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf : text = %{localtime}: \x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out11.avi

  I am trying to figure out how to add a timestamp in a formatable manner (specifically, I'd like to show mm:ss). I think this should be possible using a command like

  Code : Select all
  ffmpeg -i input.avi -vf "drawtext=fontfile=/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans-Bold.ttf:expansion=normal:text='%expr=floor(t/60)~:%expr=floor(t)' : fontcolor=white " output.avi

  But I just get a lot of

  Code : Select all
  [Parsed_drawtext_0 @ 0x1a68a80] %expr=floor(t/60) is not known

  and no text is displayed.

  If I try

  Code : Select all
  ffmpeg -i input.avi -vf "drawtext=fontfile=/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans-Bold.ttf:expansion=normal:text='%expr' : fontcolor=white " output.avi

  I get instead

  Code : Select all
  [Parsed_drawtext_0 @ 0x2d22be0] %expr requires at least 1 arguments

  so the version of drawtext I have definitely recognizes the expr function, but I can't figure out the syntax for giving it an argument. Does anyone know what the synatax is for the expr (or e) function ?

  Alternately, if there is another way to display the timecode as mm:ss that would be great too. I know that using the 'timecode' argument of drawtext you can get hh:mm:ss:ff, or using text='%pts' gives me decimal seconds to the microsecond, but I am sure that my advisor (who is very picky) will not accept either of these. Thanks in advance for any assistance !