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• How to use the blackframe avfilter of ffmpeg in C/C++

  19 juillet 2022, par luchengbiao

  I want to capture the first-not-black frame for a video as its preview ; I looked at sample which came with FFmpeg examples :

  



      /*
 * Copyright (c) 2010 Nicolas George
 * Copyright (c) 2011 Stefano Sabatini

/**
 * @file
 * API example for decoding and filtering
 * @example filtering_video.c
 */


  



  But how can I use the "blackframe" filter in C/C++ ?

  


• cmake installation of x265 for ffmpeg on Cygwin - executable location different from other codecs

  6 mai, par bballdave025

  TL ;DR (with expected vs. real)

  


  For a Cygwin build of ffmpeg, I'm installing x265, and it seems to me that the executable ends up in the wrong place. I'll show some basic directory structure, then I'll show the tree outputs for expected and real, both before and after the cmake installation. For directories where I think this is important, I'll show the outputs before and after the cmake installation.

  


  My question has two parts. I used the following cmake and make commands,

  


  # pwd => $HOME/programs/ffmpeg/ffmpeg_sources/x265/build/linux
PATH="$HOME/programs/ffmpeg/bin:$PATH" \
  cmake -G "Unix Makefiles" \
        -DCMAKE_INSTALL_PREFIX="$HOME/programs/ffmpeg/ffmpeg_build" \
        -DENABLE_SHARED=OFF \
        -DCMAKE_EXE_LINKER_FLAGS="-static" 
            ../../source
PATH="$HOME/programs/ffmpeg/bin:$PATH" make -j $(nproc)
make install


  


  The result is below, with my real vs. expected, and there is a more detailed, more explicit, and hopefully more clear file with the info. at pastebin.com/86wHrtxR.

  


  Edit : I've made a copy of the detailed/explicit/clear file on my GitHub as a gist. This should be more secure. (The Pastebin version still exists, in case that is your preference.)

  


  Now, for my two-part question :

  


  


  1. How can I change my cmake command so that my x265.exe file ends up in $HOME/programs/ffmpeg/bin with the proper linking, rather than $HOME/programs/ffmpeg/ffmpeg_build/bin ?

     


  


  2. Would the build/linker/whatever figure things out for the ffmpeg build ?

     


  


  


  I want to know the answer to question number 1 regardless of the answer to question number 2. I haven't used cmake with the -DVAR=var flags before, and I'd like to take this opportunity to learn.

  


  For the result :

  


  Things surrounded by double curly brackets are {{ expected }}.

  


  Things surrounded by double angle brackets are << real >>, i.e. they exist after the installation is done.

  


  If real matches expected, and the file/directory is new, I've surrounded it by double parentheses, i.e. double round brackets. (( match ))

  


  If something is not new (and thus has the same before and after) I haven't marked it.

  


     me@MACHINE ~/programs/ffmpeg&#xA;   $ tree --charset=ascii bin&#xA;   bin&#xA;   |-- lame.exe&#xA;   |-- mp3rtp.exe&#xA;   |-- mp3x.exe&#xA;   `-- x264.exe&#xA;{{ `-- x265.exe                     }} ## Expected, not Exists&#xA;&#xA;   me@MACHINE ~/programs/ffmpeg&#xA;   $ tree --charset=ascii \&#xA;                   ffmpeg_build&#xA;   ffmpeg_build&#xA;&lt;&lt; |-- bin                          >> ## Not expected, Exists&#xA;&lt;&lt; |   `-- x265.exe                 >> ## Not expected, Exists&#xA;   |-- include&#xA;   |   |-- fdk-aac&#xA;   |   |   |-- aacdecoder_lib.h&#xA;   |   |   |-- aacenc_lib.h&#xA;   |   |   `-- ... <more files="files">&#xA;   |   |-- lame&#xA;   |   |   `-- lame.h&#xA;   |   |-- x264.h&#xA;   |   `-- x264_config.h&#xA;(( |   |-- x265.h                   )) ## Expected and Exists&#xA;(( |   `-- x265_config.h            )) ## Expected and Exists&#xA;   |-- lib&#xA;   |   |-- libfdk-aac.a&#xA;   |   |-- libfdk-aac.la&#xA;   |   |-- libmp3lame.a&#xA;   |   |-- libmp3lame.la&#xA;(( |   |-- libx265.a                )) ## Expected and Exists&#xA;   |   `-- pkgconfig&#xA;   |       |-- fdk-aac.pc&#xA;   |       `-- x264.pc&#xA;(( |       `-- x265.pc              )) ## Expected and Exists&#xA;   `-- share&#xA;       |-- doc&#xA;       |   ... <only lame="lame">&#xA;       `-- man&#xA;           ... <only lame="lame">&#xA;</only></only></more>

  


  Other, possibly useful information about the build directory structure.

  


  me@MACHINE ~/programs/ffmpeg
$ tree --charset=ascii -L 1 .
.
|-- bin
|-- ffmpeg_build
`-- ffmpeg_sources

3 directories, 0 files


  


  For this next, ffmpeg_sources dir, I'm showing the after (which is both expected and real/exists) surrounded by double parentheses, i.e. double round brackets, (( <after> ))</after>.

  


     me@MACHINE ~/programs/ffmpeg
   $ tree --charset=ascii -L 1 ffmpeg_sources
   ffmpeg_sources
   |-- fdk-aac.zip
   |-- lame-svn
   |-- mstorsjo-fdk-aac-e7d8591
   |-- x264-snapshot-20191217-2245
   |-- x264-snapshot-20191217-2245.tar.bz2
   `-- x264-snapshot-20191218-README.txt
(( `-- x265                         ))

   3 directories, 3 files
(( 4 directories, 3 files ))


  


  ---

  


  NOW, FOR SOME MORE DETAIL

  


  ---

  


  What I'm Doing

  


  I am working on a Cygwin build (vs. a Windows/mingw build) of ffmpeg. I am following an older guide by koohiimaster (archived). That guide says,

  


  


  [W]e are not cross-compiling for windows ; we are compiling for Cygwin.

  


  


  This 2014 guide doesn't have all of the codecs I want - I want as complete a build as possible - so I've also been referring to this ffmpeg-for-Ubuntu guide (archived), which I hope is kept up-to-date. It's referred to by koohiimaster.

  


  Also, as a way of checking that I'm getting all the codecs I want, I've been looking at this FFmpeg for Windows guide from SuperUser

  


  I'll give the basics of my steps below. More details, as well as all the output is at pastebin.com/suL1nU6Z.

  


  Edit : I've put the log of terminal input/output for all my steps into a gist at my GitHub as this seems safer than Pastebin.

  


  A look at directory structure for the build

  


  me@MACHINE ~/programs/ffmpeg
$ cd $HOME/programs/ffmpeg

me@MACHINE ~/programs/ffmpeg
$ tree --charset=ascii -d -L 1
.
|-- bin
|-- ffmpeg_build
`-- ffmpeg_sources

3 directories


  


  Getting the source. Note that I had to apt-cyg install mercurial, though (with my Cygwin setup GUI/EXE in my Cygwin root directory, i.e. C:\cygwin64\setup-x86_64.exe), I could also have done /setup-x86_64.exe install -q -P mercurial.

  


  cd ffmpeg_sources
hg clone https://bitbucket.org/multicoreware/x265


  


  Running the cmake and make commands

  


  cd x265/build/linux
PATH="$HOME/programs/ffmpeg/bin:$PATH" \
  cmake -G "Unix Makefiles" \
        -DCMAKE_INSTALL_PREFIX="$HOME/programs/ffmpeg/ffmpeg_build" \
        -DENABLE_SHARED=OFF \
        -DCMAKE_EXE_LINKER_FLAGS="-static" \
            ../../source
PATH="$HOME/programs/ffmpeg/bin:$PATH" make -j $(nproc)
make install


  


  It was the last part (actually the very last line) of the make install output that worried me. Here is the whole output - it's not very long.

  


  make[1]: Entering directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
make[2]: Entering directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
make[2]: Leaving directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
[ 20%] Built target encoder
make[2]: Entering directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
make[2]: Leaving directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
[ 83%] Built target common
make[2]: Entering directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
make[2]: Leaving directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
[ 84%] Built target x265-static
make[2]: Entering directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
make[2]: Leaving directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
[100%] Built target cli
make[1]: Leaving directory '/home/me/programs/ffmpeg/ffmpeg_sources/x265/build/linux'
Install the project...
-- Install configuration: "Release"
-- Installing: /home/me/programs/ffmpeg/ffmpeg_build/lib/libx265.a
-- Installing: /home/me/programs/ffmpeg/ffmpeg_build/include/x265.h
-- Installing: /home/me/programs/ffmpeg/ffmpeg_build/include/x265_config.h
-- Installing: /home/me/programs/ffmpeg/ffmpeg_build/lib/pkgconfig/x265.pc
-- Installing: /home/me/programs/ffmpeg/ffmpeg_build/bin/x265.exe


  


  As discussed in the TL ;DR section, I expected to see x265.exe at

  


  home/me/programs/ffmpeg/bin/x265.exe

  


  rather than the path given on the last line of output,

  


  /home/me/programs/ffmpeg/ffmpeg_build/bin/x265.exe

  


  This worries me especially because the first part of the ffmpeg install command that my instructions inform me to run is

  


  PATH="$HOME/programs/ffmpeg/bin:$PATH" \
PKG_CONFIG_PATH="$HOME/programs/ffmpeg/ffmpeg_build/lib/pkgconfig" \
  ./configure \
    --prefix="$HOME/programs/ffmpeg/ffmpeg_build" \
    --extra-cflags="-I$HOME/programs/ffmpeg/ffmpeg_build/include" \
    --extra-ldflags="-L$HOME/programs/ffmpeg/ffmpeg_build/lib" \
    --bindir="$HOME/programs/ffmpeg/bin" \


  


     ... and on it goes ...

  


  It would seem to me that the .configure script for ffmpeg won't find the x265 executable, since it's not in the bindir.

  


  I'll repeat my two-part question from before :

  


  

  1. How can I change my cmake command so that my x265.exe file ends up in $HOME/programs/ffmpeg/bin with the proper linking, rather than $HOME/programs/ffmpeg/ffmpeg_build/bin ?

  


  


  What I'm looking for here is something akin to the --bindir flag from make's ./confiure.

  


  

  2. Would the build/linker/whatever figure things out for the ffmpeg build ?

  


  


  I want to know the answer to question number 1 regardless of the answer to question number 2. I haven't used cmake with the -DVAR=var flags before, and I'd like to take this opportunity to learn.

  


  ---

  


  Where I've Looked & What I've Tried

  


  I first started with the man page and the --help for cmake. That was scary. I was hoping that I'd find something useful around the CMAKE_INSTALL_PREFIX stuff, but I wasn't sure what to make of it.

  


  I tried greping through cmake --help-full (with 50 lines before and after whatever I was searching for), but got tripped up by the complexity. I've only used basic cmake stuff, before, and I got more than a little lost.

  


  Even with the --help, I don't know if I need to look at the help-manual, the help-command, the help-module, the help-policy, the help-variable, or something else.

  


  It seemed to me, in reading, that a "binary directory" is the top of the "build", whereas I thought it would be the dir named bin ... I couldn't tell what things were meant to be used by the person creating the package rather than by me, who am trying to make/build the package from the command line.

  


  I looked through what seemed to be a cmake wiki's Useful Variables page (archived), as well as at this thread at cmake.org (archived), which, along with this SO source and this and this and this and this SO sources, seemed to suggest using the CMAKE_RUNTIME_OUTPUT_DIRECTORY variable (since the EXECUTABLE_OUTPUT-DIRECTORY variable has been superseded by it). By the way, I couldn't tell which things should be used by the creator of the package vs. the consumer of the package - the consumer being me. I tried with

  


  PATH="$HOME/programs/ffmpeg/bin:$PATH" \
  cmake -G "Unix Makefiles" \
        -DCMAKE_INSTALL_PREFIX="$HOME/programs/ffmpeg/ffmpeg_build" \
        -DCMAKE_RUNTIME_OUTPUT_DIRECTORY="$HOME/programs/ffmpeg/bin" \
        -DENABLE_SHARED=OFF \
        -DCMAKE_EXE_LINKER_FLAGS="-static" 
            ../../source
PATH="$HOME/


  


  and have thought about fifty-or-so other -DVAR variables, but with any I have tried, I still get the same result. I still get the executable in what seems to be the wrong place.

  


  ---

  


  System Details

  


  $ date && date +'%s'
Tue, May  5, 2020 11:14:40 AM
1588698880
$ uname -a
CYGWIN_NT-10.0 MACHINE 3.1.4(0.340/5/3) 2020-02-19 08:49 x86_64 Cygwin
$ cmake --version
cmake version 3.14.5

CMake suite maintained and supported by Kitware (kitware.com/cmake).
$ bash --version | head -n 1
GNU bash, version 4.4.12(3)-release (x86_64-unknown-cygwin)
$ gcc --version | head -n 1
gcc (GCC) 9.3.0
$ g++ --version | head -n 1
g++ (GCC) 9.3.0
$ make --version | head -n 2
GNU Make 4.3
Built for x86_64-pc-cygwin


  


• Why do you need analytics for your WordPress ?

  7 avril 2020, par Joselyn Khor — Analytics Tips, Plugins
  Not many people know this, but having a WordPress analytics tool gives you a competitive advantage. It’s also essential to the growth of your website. For many businesses, websites are the main driver of revenue and sales. In the case of blogs, it’s your first chance to make a lasting impression.

  Now, maybe you’ve heard of Google Analytics or even the privacy-friendly alternative, Matomo Analytics, but have never tried them ? These are analytics platforms that help you understand your website traffic and visitors. (You can find these platforms as plugins in the WordPress directory !)

  They’re important because the insights you get help you determine what changes to make to improve your website. Without them you could face a tougher time figuring out what’s working, what the issues are (and solving them before they get out of hand), and making sure you’re taking your website in the right direction. 

  WordPress analytics gives you an understanding of what’s actually going on.

  How does a WordPress analytics plugin benefit your website ?

  What this means for you is getting a toolkit to learn how to get more sales or followers and subscribers (aka conversions in analytics terms). 

  By getting insights into user behaviour, content performance, and how you can optimise your website, you can reach more of your goals, like increasing sales or growing your audience.

  A WordPress analytics tool helps you get more traffic to your site

  You get a range of features which tell you which acquisition channels are working for you like – social media, search engines, and other websites mentioning you. This helps you make an informed decision on where to focus energies (or spend) to get more of the ideal people coming through to your website. 

  

  Example : Looking through your acquisition channels and seeing that Reddit drives a lot of traffic through to your website. Since this channel seems to be working for you, you could then spend more time on Reddit posts to increase traffic.

  But getting more traffic isn’t all there is to it. Once they land on your site, you want them to stay for a little longer so they are intrigued by what you’re offering. Be it a product, or awesome content.

  Which leads us to …

  Increasing engagement by learning about visitor behaviour

  When you get a solid number of visitors on your website, it’s good to then learn about how they behave on your site. A WordPress analytics tool helps with engagement since you’re seeing what’s appealing to them, and what isn’t.

   Increasing engagement is good for a few reasons. 

  • You end up speaking the language of your readers. 
  • You can make a difference with the information you’re putting out. 
  • You get loyal customers and believers in your organisation. 

  With more engaged visitors, you can build trust with them and eventually be able to convince them that your product, service, or blog is needed in their lives.

  

  Example : Looking through entry and exit pages to see what first impression is making them stay, and what impression is making them leave. This helps you redirect efforts to give your website a better chance of getting visitors to stay longer.

  Improving your content and engagement can lead to more conversions

  After you get visitors engaged, it’s time to convert. 

  Whether you have an ecommerce site or freelance blog, you’ll need to know how to boost conversions. This simply means getting people to achieve more of the actions you’re wanting them to take on your site. Like subscribing to your newsletter or adding items to a cart.

  With conversion optimization features, you’re finding out how well your website is designed to get buyers through a journey to conversion. 

  

  Example : Say you’ve created a newsletter sign up page, but you’re not getting as many sign ups as you’d like. With a web analytics tool, you can look into it further. A funnels feature could tell you how they’re getting to that page. If people can’t find your page, that could be reason for low conversion rates. Or, maybe you are getting people landing on this page, but you can’t tell why they’re not signing up. Try setting up a heatmap to see how far they’re scrolling down your page to the sign up section. Through these conversion optimization features, you can make tweaks that significantly improve conversions.

  So, how does the Matomo Analytics for WordPress plugin help with all of this ?

  

  Matomo Analytics for WordPress is a free web analytics plugin that gives you access to all the features mentioned above, right in your own WordPress dashboard. It’s completely free to use and is handy for users of all skill levels. From beginners right through to advanced analysts. 

  You get to move through all the stages to increase traffic, increase engagement, and convert. By using Matomo for WordPress, you put yourself in a better position to track all the needed data from your WordPress website. 

  You have this toolkit to improve your website for free, with a few clicks ! 

  By getting useful insights like visitors, acquisitions, bounce rates etc. you gain a new perspective on how to improve your website so it’s better at doing what you created it to do. Getting these insights also means giving yourself the confidence to do what’s best for your website in a data-driven way. 

  With all this knowledge, you can be competitive, or grow enough that you’re leaving your competitors in the dust.