Recherche avancée

Sur d’autres sites (12793)

• Unable to get the original quality after resizing in ffmpeg

  24 septembre 2018, par Sabha

  I am trying to resize a high res video into 480x ??? and with to maintain aspect ratio and also without losing quality. I wish to maintain the original quality of the video. I tried this command line but it loses quality.

  ffmpeg -i a.mp4 -filter:v scale=480:-1 -c:a copy b.mp4

  I got some filters and options from google search such as -qscale,-sameq etc but it is not working.

  Can you please tell me the exact command ?

  Thanks

  EDIT : I also need to place two videos one below the other and wish to know if there is any such option in ffmpeg coz I cannot find anything on google.

• How to make ffmpeg respect the "start_time" variable when combining cdg and mp3 ?

  5 juillet 2020, par Steffen Poulsen

  I'm trying to combine two .cdg and .mp3 files because I want to make a single .mkv file out of them.

  



  When I do it I get a .mkv file alright, but the audio is unfortunately not synced with the video.

  



  So, I was wondering why this is ? Apparently I must be missing a parameter on my command or something.

  



  What I do is this :

  



  ffmpeg -y -i song.cdg -i song.mp3 -pix_fmt yuv420p -vcodec libx264 -acodec copy song.mkv


  



  It works fine, but in this particular case the result is out of sync by 1.2 seconds. This varies per song, from 0 to a couple of seconds.

  



  However, if I do a ffprobe on the .cdg file I notice that this number is already present, as the "start_time" variable :

  



  ffprobe -v error -show_format -show_streams song.cdg
...
start_time=1.186667
...


  



  So, if I just use this number directly as this for the -itsoffset parameter :

  



  ffmpeg -y -itsoffset 1.186667 -i song.cdg -i song.mp3 -pix_fmt yuv420p -vcodec libx264 -acodec copy song.mkv


  



  Then the video and audio is in perfect sync.

  



  So, I am wondering - what parameter do I need to add to my command to have ffmpeg respect this variable ?

  


• macOS compile FFMpeg as static standalone binary

  27 octobre 2019, par ColdSteel

  I am trying to compile ffmpeg for macOS (from macOS) as static binary for several days with no luck.
  Here is a script I am running to compile the FFmpeg binary

  cd /Users/$USER/ffmpeg/macOSBuild
  
  basePath=/macOSdependencies/DependenciesOutput
  
  
  
  export LD_LIBRARY_PATH="/Users/romanlevin/ffmpeg/macOSdependencies/DependenciesOutputbasePath/SDL2/lib/“
  
  
  
  ../configure --disable-autodetect --pkg-config-flags="--static" --extra-cflags="-I$basePath/SDL2/include/" --extra-ldflags="-L/Users/romanlevin/ffmpeg/macOSdependencies/DependenciesOutput/SDL2/lib/" --prefix=/usr/local --enable-gpl --enable-version3 --enable-sdl2 --enable-static --disable-shared
  
  
  
  make clean
  
  make -j8

  However it is always linking SDL2 as dynamic lib.

  Please note I have compiled the SDL2 by myself and put it in the directory I am trying to add to ld

  

  However I also have SDL2 installed with brew, but I don’t want to use it.
  I want Ffmpeg to pick compiled SDL2.

  It does looking for my Compiled library but only asdylib in a hardcoded path - which means I can’t get a portable binaries :(.

  Could some1 open my eyes on what am I doing wrong please ?