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• splitting a precise .ts piece with ffmpeg when doing -c:v copy

  13 février 2016, par Ivo

  The goal is to generate HLS-compatible MPEGTS pieces from a mkv, copying the video with -c:v copy, but transcoding the audio.

  However, since on input seeking (-ss) ffmpeg seeks to keyframe (for me, that seems to be nearest previous keyframe), I’m getting N seconds of video without audio before most of the segments, starting from the keyframe.

  Possible solutions are :

  1. Define segment offset/duration so that it actually matches the keyframes ; problem is I don’t know how to quickly extract the list of keyframes and their offsets

  2. Force ffmpeg to seek to the proper time somehow, and generate a keyframe there to start the segment with ; EDIT : I assume this is impossible since generating a keyframe changes all frames after that, which is impossible with -c:v copy

  Please do not suggest existing HLS solutions unless they demonstrate in source code a solution to the problem. ffmpeg has to be used, to generate each segment on-demand.

• Assigning variable a home file path returns warning

  28 mai 2015, par Code_Ed_Student

  I am working with ffmpeg and bash. The question that follows is more in relation to bash scripting variable assignment. I compiled ffmpeg from source using the guide. There are two ways to invoke ffmpeg : cd ~/bin && ./ffmpeg -i ~/input.mp4 ~/videos/output.mkv or /home/yourusername/bin/ffmpeg ... . However in my script I am trying to set path to a variable and it returns the error Using a password on the command line interface can be insecure. How can I properly call the program without this warning ?

  #!/bin/bash/
  
  ffprobe_path="/home/yourusername/bin/ffprobe"
  
  
  
  while IFS== read field value; do
  
      details[$field]="$value"
  
  done < <($ffprobe_path -i "$file" -show_format -v quiet | grep '.=.')
  
  
  
  echo "${details[duration]}"

  Result

  Warning: Using a password on the command line interface can be insecure.

• Firefox, Chrome, Safari have grey background for MP4 HTML5 video

  5 avril 2016, par James

  Any video (that I can make) with a white background becomes grey in Firefox, Chrome, and Safari (it is white in IE). Well, on my Windows machine it is grey, on my Android phone/tablet and Mac it is white...

  I am using ffmpeg to encode the video. If I encode it as webm, the background is white.

  See : https://jsfiddle.net/Lbg8f6ck/

  I found a hack that fixes it for Chrome :

  <video style="-webkit-filter:brightness(108.5%);"></video>code>

  But it does not work for Firefox or Safari.

  Another hack for Firefox :

  filter:brightness(1.085)

  But for some reason setting it through JavaScript does not work.

  A few versions ago the background was white for Chrome, then became grey again...

  The question is : Why is white grey ?

  Is it an issue with the video or with Chrome, Firefox, Safari in general ? (How can they not support white ?)

  Is it possible to get a white background ?

  Any hacks, workarounds ?