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• How To Concatenate Two MP4 Videos With Different Aspect Ratios and Resolutions

  11 novembre 2017, par PortableDiag

  I am using ffmpeg to concatenate multiple MP4 videos, two at a time. The problem I am having is that the videos are often different resolutions and aspect ratios. One might come from a 480p webcam with a 1:1 aspect ratio and the other a brand new iPhone with 4k video and rectangular aspect ratio. Currently I must choose and set the aspect ratio manually and this results in one of the two videos becoming distorted, depending on the selected aspect ratio.

  How can I merge two videos so that the overall viewing field has a square aspect ratio but videos with a rectangular aspect ratio will be scaled to fit inside.

  I am using this command to merge the videos :

  ffmpeg -threads 1 -i '/518.mp4' -i '/516.mp4' -y -filter_complex "[0:v]scale=1080x1920,setpts=PTS-STARTPTS,setdar=0/1[v0];[1:v]scale=1080x1920,setpts=PTS-STARTPTS,setdar=0/1[v1];[v0][0:a][v1][1:a]concat=n=2:v=1:a=1" '/partial1.mp4'

  This is the result : https://www.dropbox.com/s/x1un7z1ljwr6tty/merged_newsort.mp4?dl=0

  Is it possible to apply a border to the rectangular video to give them a square aspect ratio ?

  How can I keep prevent distortion from occurring during the merge process ?

  Thanks in advance.

• How can I overlay an angled gradient or fade over the corner of a video with ffmpeg ?

  16 février 2021, par grgoelyk

  I want to darken the corner of a video with a (for instance) 45-degree black gradient. I'd like to customize the angle, feathering, color and opacity. My video is 10-bit UHD HEVC and I need to output to 10-bit lossless intermediate (probably v210 codec). How can I do all of this in ffmpeg ?

  


  Here is a mockup of what I want to do :

  


  

  


• WebRTC books – a brief review

  1er janvier 2014, par silvia

  I just finished reading Rob Manson’s awesome book “Getting Started with WebRTC” and I can highly recommend it for any Web developer who is interested in WebRTC.

  Rob explains very clearly how to create your first video, audio or data peer-connection using WebRTC in current Google Chrome or Firefox (I think it also now applies to Opera, though that wasn’t the case when his book was published). He makes available example code, so you can replicate it in your own Web application easily, including the setup of a signalling server. He also points out that you need a ICE (STUN/TURN) server to punch through firewalls and gives recommendations for what software is available, but stops short of explaining how to set them up.

  Rob’s focus is very much on the features required in a typical Web application :

  • video calls
  • audio calls
  • text chats
  • file sharing

  In fact, he provides the most in-depth demo of how to set up a good file sharing interface I have come across.

  Rob then also extends his introduction to WebRTC to two key application areas : education and team communication. His recommendations are spot on and required reading for anyone developing applications in these spaces.

  —

  Before Rob’s book, I have also read Alan Johnson and Dan Burnett’s “WebRTC” book on APIs and RTCWEB protocols of the HTML5 Real-Time Web.

  Alan and Dan’s book was written more than a year ago and explains that state of standardisation at that time. It’s probably a little out-dated now, but it still gives you good foundations on why some decisions were made the way they are and what are contentious issues (some of which still remain). If you really want to understand what happens behind the scenes when you call certain functions in the WebRTC APIs of browsers, then this is for you.

  Alan and Dan’s book explains in more details than Rob’s book how IP addresses of communication partners are found, how firewall holepunching works, how sessions get negotiated, and how the standards process works. It’s probably less useful to a Web developer who just wants to implement video call functionality into their Web application, though if something goes wrong you may find yourself digging into the details of SDP, SRTP, DTLS, and other cryptic abbreviations of protocols that all need to work together to get a WebRTC call working.

  —

  Overall, both books are worthwhile and cover different aspects of WebRTC that you will stumble across if you are directly dealing with WebRTC code.