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• What’s So Hard About Building ?

  10 septembre 2011, par Multimedia Mike — Programming

  I finally had a revelation as to why so building software can be so difficult– because build systems are typically built on programming languages that you don’t normally use in your day to day programming activities. If the project is simple enough, the build system usually takes care of the complexities. If there are subtle complexities — and there always are — then you can to figure out how to customize the build system to meet your needs.

  First, there’s the Makefile. It’s easy to forget that the syntax which comprises a Makefile pretty well qualifies as a programming language. I wonder if it’s Turing-complete ? But writing and maintaining Makefiles manually is arduous and many systems have been created to generate Makefiles for you. At the end of the day, running ‘make’ still requires the presence of a Makefile and in the worst case scenario, you’re going to have to inspect and debug what was automatically generated for that Makefile.

  So there is the widespread GNU build system, a.k.a., “the autotools”, named due to its principle components such as autoconf and automake. In this situation, you have no fewer than 3 distinct languages at work. You write your general build instructions using a set of m4 macros (language #1). These get processed by the autotools in order to generate a shell script (language #2) called configure. When this is executed by the user, it eventually generates a Makefile (language #3).

  Over the years, a few challengers have attempted to dethrone autotools. One is CMake which configures a project using its own custom programming language that you will need to learn. Configuration generates a standard Makefile. So there are 2 languages involved in this approach.

  Another option is SCons, which is Python-based, top to bottom. Only one programming language is involved in the build system ; there’s no Makefile generated and run. Until I started writing this, I was guessing that the Python component generated a Makefile, but no.

  That actually makes SCons look fairly desirable, at least if your only metric when choosing a build system is to minimize friction against rarely-used programming languages.

  I should also make mention of a few others : Apache Ant is a build system in which the build process is described by an XML file. XML doesn’t qualify as a programming language (though that apparently doesn’t stop some people from using it as such). I see there’s also qmake, related to the Qt system. This system uses its own custom syntax.

• ffmpeg filtre ocr and ocv

  21 août 2016, par user3689259

  i want to know how to use Filtre ocr and ocv , on FFmpeg . i dont find any doc for the 2 filter ffmpeg .
  this is doc on ffmpeg

  Optical Character Recognition
  
  
  
  This filter uses Tesseract for optical character recognition.
  
  
  
  It accepts the following options:
  
  
  
  datapath
  
  
  
      Set datapath to tesseract data. Default is to use whatever was set at installation.
  
  language
  
  
  
      Set language, default is "eng".
  
  whitelist
  
  
  
      Set character whitelist.
  
  blacklist
  
  
  
      Set character blacklist. 
  
  
  
  The filter exports recognized text as the frame metadata lavfi.ocr.text. 

• Pick 2 lang stream and one video ffmpeg

  7 juin 2023, par Gwildor

  Please help me. I have try alot of diffrent code to get this to work, but i can't fix it. So now im going to try to get pro help from you :)

  


  I use this code, it works perfect, but it select all audio stream from eng and swe. How can i get only ony stream of eng and swe audio and one video ?

  


  for f in /mnt/re-encode/*/*.mkv_; do /usr/local/bin/ffmpeg -fflags +igndts -analyzeduration 2147483647 -probesize 2147483647 \ -hide_banner -sn -err_detect ignore_err -init_hw_device vaapi=foo:/dev/dri/renderD128 -hwaccel vaapi -hwaccel_output_format vaapi -hwaccel_device foo -i "$f" \ -b:v 6M -minrate 6M -maxrate 6M -bufsize 6M \ -profile:v 100 -level 41 -bf 0 -r film -sn -movflags +faststart+write_colr+prefer_icc \ -map 0:v:0 -map 0:a:m:language:eng? -map 0:a:m:language:swe? -filter_hw_device foo -vf "deinterlace_vaapi,scale_vaapi=w=-2:h=720,hwdownload,format=nv12|vaapi,subtitles='${f%.*}.srt',hwupload" -c:v h264_vaapi \ -c:a:0 aac -ac 2 -af "volume=2" -b:a 256k \ -f mp4 -y -hide_banner "${f%.*}_b.mp4_"

  


  I have tryc pipe : and /dev/null