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• Remove frames based off an image with FFmpeg

  15 novembre 2020, par VEXED

  The Goal : Take a frame or a reference image and use that to decide what frames to keep/remove from an old screen recording (no audio).

  


  To be slightly more specific, I want to match a specific program that is being used in the screen recording. The program is always full screen and could potentially be identified just by a crop of the top left corner.

  


  The Question : What would be the best way to take an image, in particular a cropped corner of say 100px width and height, and look for the same matching corner in a video ? I would want to output those matches to a new file, that or remove the non-matching frames and create a new file with all the frames that match.

  


  What I Know : I know that duplicate frame removal is very possible, and I already use that for screen recordings.

  


  -filter:v mpdecimate, setpts=N/FRAME_RATE/TB \


  


  The above is being used in my screen recording script to remove duplicate frames.

  


  I'm also aware that you can crop using FFmpeg, but I'm not looking to have actual cropped output. I'm only looking to use a crop to find the portion that matches my reference image or reference frame.

  


  ffmpeg -i in.mp4 -filter:v "crop=out_w:out_h:x:y" out.mp4


  


  The above is a basic crop.

  


  The only reference to finding frames by images is this one. It didn't do what I wanted and just produced dark and distorted output. Though I might be understanding what the aim of that post was incorrectly.

  


  Notes : Thanks in advance for any help, this frame/image matching doesn't have to be done while recording, but can be done in post.

  


• Introducing the Piwik Java Tracker – Analytics for your Java based applications

  18 novembre 2015, par Brett — Community, Development

  Hello Piwik Community !

  My name is Brett Csorba, a Software Engineer out of the US. I’d like to introduce the Piwik Java Tracker project, an easy way to track usage data within your Java applications !

  When would I need to track users in a Java application ? What’s wrong with front end tracking ?

  Absolutely nothing ! We encourage users to track information where it makes the most sense for them ! But in cases where

  • you have a 100% Java based application
  • you expose a REST layer where users can bypass your front end tracking code
  • you have valuable data you want to track that is unnecessary or too sensitive to pass back to the user

  the Piwik Java Tracker can help you track the data you need.

  What exactly can it track ?

  We aim to provide the full Tracking HTTP API. If you find we’ve left something out by mistake, let us know !

  You’ve sparked my curiosity, how would I use such a thing ?

  Well, once you’ve installed Piwik and set up your first website, you can grab the latest jar and include it in your project. The dependencies needed to both use and test this library can be found here.

  This library is intended to be used for projects that support Java 8. The released binaries are built, tested, and deployed from Oracle JDK 8.

  Using this API is as simple as creating a new request

  PiwikRequest request = new PiwikRequest(1, new URL("http://my-site.com/action")) ;

  Setting some more information if you want to

  request.setActionName("myAction") ;
  request.setPageCustomVariable("key", "value") ;

  and firing the request.

  PiwikTracker tracker = new PiwikTracker("http://your-piwik-domain.tld/piwik.php") ;
  HttpResponse response = tracker.sendRequest(request) ;

  Check out this guide to using the API for some more information !

  Looks cool so far, can I help out ?

  Yes ! Absolutely ! Download the project, try it, break it without mercy ! (Just make sure you tell us how.) Contribute to the project or let us know what we can do to it to improve it. As with all open source projects, we need your help to improve it.

• Generating a P frame based on an I frame

  17 octobre 2016, par Navid Ahmadi

  Say I have 5 images that are quite similar. I’d like to compress images 2, 3, 4 and 5 based on the first image, somewhat similar to the way P frames are generated from an I frame.

  • In general, what’s the best way/tool to do so ?
  • For instance, using FFMPEG, is it possible to generate P frames and store them in a separate file ?

  Edit :
  Although similar, I am not looking for simply generating a diff between the two images. My goal is to somehow use the information in the first image to make the consecutive images much smaller. If I simply do a diff, the diff itself is about the same size (about 10% reduced) which is not as much as I expect. If I generate a mp4 video including these 5 frames, the video size is much less than putting 5 frames in a file, which probably has to with frame predications based on the I frames. Is there a way to generate those predicted frames one by one and store them individually ?