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• Build a C++ project with OpenCV 4.5.x in Visual Studio with custom flags for ffmpeg

  18 mai 2022, par Ivy Growing

  Our C++ project in MS Visual Studio under Windows 10 uses OpenCV 4.5.

  


  #include <opencv2></opencv2>opencv.hpp>&#xA;#include <opencv2></opencv2>videoio.hpp>&#xA;#include <opencv2></opencv2>imgcodecs.hpp>&#xA;#include "opencv2/highgui/highgui.hpp"&#xA;#include "opencv2/core/core.hpp"&#xA;

  


  The project works well. The OpenCV uses ffmpeg as dependency for extracting video frames from a stream or a file. Our legals require following flags are not used when compiling the ffmpeg to approve the product release :

  


  

  • without --enable-gpl

  


  • without --enable-nonfree

  


  


  So far this page gets close to the answer, however, I cannot understand how to configure the Visual Studio to use custom flags just for ffmpeg and not for other dependencies. Elaboration is appreciated.

  


  The Visual Studio has challenging and pretty confusing (for me in person, often) menues and settings. This is the root of the question :

  


  How/where in Visual Studio can I see which flags are used for compiling of dependent libraries ?
Specifically, how can I check which flags are used in OpenCV to build the ffmpeg ?

  


• Create animated Gif in Kotlin

  27 octobre 2022, par Gregor Sotošek

  I am struggling with something I thought would be a piece of cake. In my Android App (jetpack compose variant), I want to save some screenshots (not many, 10-20 of them), and then "packed them" into animated GIF file, and then user would be able to share this GIF to other users. I am having a hard time "creating" or "saving" GIF file from saved screenshots. The only thing I found on web was pretty old post here

  


  1 : How to create an animated GIF from JPEGs in Android (development) but I just can't get it to work. All the others posts are related to "displaying" GIF in android, which is not my problem currently. If someone can point me in the right direction, would be very nice.

  


  I also try to make it to work with FFmpeg, but don't know how to either.
https://proandroiddev.com/a-story-about-ffmpeg-in-android-part-i-compilation-898e4a249422

  


  Thank you

  


• Remux video file and get the output bytes on the fly

  22 septembre 2014, par Miguel Botón

  I have been looking for a solution too many hours and maybe I didn’t use the proper keywords to find it but I give up. I hope somebody can help me with this.

  My goal is to create a small C code that remux a video file to another container (mp4 or whatever, not decided yet) and create a JNI interface to read the raw output bytes in my Java application.

  Create the JNI interface is not a problem and remux the video is pretty simple (and there is a great example at http://ffmpeg.org/doxygen/trunk/doc_2examples_2remuxing_8c-example.html), but I’m having a headache trying to figure out how I can tell FFmpeg to deliver the data when my application requests it.

  I was thinking in create a thread, where the remux would be done, and write the output data to a buffer where my application would read it. When the buffer is full the remux would be paused until it is flushed, but I don’t know how I can achieve that or if it would be a proper solution.

  I believe the best solution will involve creating an AVIOContext but I’m not very sure.

  Thank you very much in advance.

  EDIT :

  A solution I found, but I don’t like it at all, is to run the "ffmpeg" executable, tell it to write the output to "stdout" and read this output from my Java application using an InputStream.