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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 ?

  


• Proprietary codecs on Linux. What is legal ?

  17 octobre 2016, par George Eco

  So, assuming we got a distribution without proprietary codecs installed.
  Let’s take Linux Mint for example. I want to store and playback wav and ogg format sounds, either by using my own software, or by using another developer’s software. So far so good right ?

  Imagine now that we have the following scenario. For some reason, I wanna playback a file that is either an mp4 or mp3 or mpeg or any other format, made by proprietary codecs. Instantly, I will need a codec for these formats.

  I read somewhere that Fluendo sells solutions for "legal codec usage" for linux distros.
  URL of fluendo : http://www.fluendo.com/en/

  So here comes the questions :

  Using VLC and ffmpeg is enough for me to convert a file to an ogg or ogv so I can playback a song or a video using an open format. You can also playback playback files made by proprietary formats. But are VLC and ffmpeg legal to use, to playback such files made by proprietary codecs ? For example, ss VLC codecs okay to be used without paying anyone for mp4 playback ? Is it okay to convert a file from mp4 to ogv ?
  If not, are there any legal and open source and free (as in freedom) codecs around that can solve the issue, or does someone have to pay a product, to be ethically correct, to the developers of the proprietaty codecs ?

  Note that I do not ask for Windows, since codec licenses are included to the price of the operating system. I ask exclusively for a free linux distribution.

• lavc/flacdsp : R-V V LPC16 function

  15 novembre 2023, par Rémi Denis-Courmont

  lavc/flacdsp : R-V V LPC16 function
  In this case, the inner loop computing the scalar product can be reduced
  
  to just one multiplication and one sum even with 128-bit vectors. The
  
  result is a lot simpler, but also brings more modest performance gains :
  flac_lpc_16_13_c :       15241.0
  
  flac_lpc_16_13_rvv_i32 : 11230.0
  
  flac_lpc_16_16_c :       17884.0
  
  flac_lpc_16_16_rvv_i32 : 12125.7
  
  flac_lpc_16_29_c :       27847.7
  
  flac_lpc_16_29_rvv_i32 : 10494.0
  
  flac_lpc_16_32_c :       30051.5
  
  flac_lpc_16_32_rvv_i32 : 10355.0
  

  • [DH] libavcodec/riscv/flacdsp_init.c
  • [DH] libavcodec/riscv/flacdsp_rvv.S