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• ffmpeg scale not woking as expected it adds weird lines

  21 juin 2021, par Jintor

  When I encode without scalling, all is ok,

  


  

  


  but when I add this

  


  -vf "-2:1080" or -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setsar=1" I GET THIS :


  


  if I add w3fdif or format rgba like -vf "w3fdif,format=rgba.... i GET THIS


  


  why and how to fix this ?

  


  I tried with different .mov, .mkv

  


• ffmpeg resulting bitrate higher than expected. did i miss something ? [migrated]

  7 octobre 2013, par zantafio

  i am using ffmpeg to create some h264 transport streams.
  the bitrate for video is 496k, for audio 64k.
  However when the ( 2-pass ) encoding is done, i get a stream with more then 600k.
  i am using the following syntax in my script :

  codec=h264
  
  streamsuffix=ts
  
  audiocutoff=15000
  
  audioprofile=aac_low
  
  audiosamplerate=48000
  
  video_med=496k
  
  audio_med=64k
  
  suffix_med=_med
  
  preset=veryslow
  
  threads=4
  
  dirname="${1%/*}"
  
  filename=$(basename "$1")
  
  extension="${filename##*.}"
  
  filename="${filename%.*}"
  
  
  
  ffmpeg -i $filename"."$extension -preset $preset -strict experimental -threads $threads -c:v $codec -b:v $video_med -bsf:v h264_mp4toannexb -pass 1 -an -f rawvideo -y /dev/null 
  
  ffmpeg -y -i $filename"."$extension -preset $preset -strict experimental -threads $threads -c:a aac -cutoff $audiocutoff -profile:a $audioprofile -b:a $audio_med -ar $audiosamplerate  -c:v $codec -b:v $video_med -bsf:v h264_mp4toannexb -pass 2 $filename$suffix_med"."$streamsuffix

  did i miss something ? do i need to enforce the target bitrate ?
  thanks a lot !

• The built ffmpeg.exe is not working as expected

  29 avril 2021, par user1939578

  In my c++ application, I want to use ffmpeg lib statically.

  


  I downloaded the ffmpeg-3.4.1 source and built the statically linked ffmpeg using MINGW, Yasm and VS2015 Command prompt as follows,

  


  

  1. Downloaded the msys2-x86_64-20161025.exe

  


  2. On opening the MINGW command prompt, install the required gcc tool using command "pacman -S make gcc diffutils"

  


  3. Renamed C :\msys64\usr\bin\link.exe to C :\msys64\usr\bin\link_orig.exe

  


  4. Downloaded the yasm 32 bit exe and set it's path to PATH environment variable. ("%PATH% ;D :\ffmpeg")

  


  5. Run VS2015, and open MINGW- C :\msys64\msys2_shell.cmd -use-full-path

  


  6. On opening MingW, change pwd to ffmpeg. Run ./configure then make the make install.

  


  


  The configuration is used : ./configure —prefix="build" —toolchain=msvc —arch=x86 —enable-yasm —enable-asm —disable-shared —enable-static

  


  It is built successfully. I got the bin folder having ffmpeg.exe and ffprobe.exe. The size of ffmpeg.exe is 18 Mb. Also the 7 libs as .a file.

  


  I guess I have to convert.a files to .lib and use in application ?

  


  I wanted to confirm if I have built everything correctly. So I tried to convert a .webm file to mp4 using the built ffmpeg.exe. I found that the size of output file is very large and quality is too bad. The input.webm file size was only 15 Mb and output.mp4 file size was about 188 Mb.

  


  Then I downloaded the statically link ffmpeg application from https://ffmpeg.zeranoe.com/builds/. I see the size of ffmpeg.exe is about 35 Mb and It works fine. For same .webm file, it created .mp4 file only 44 Mb and quality is also ok. I figured out that it is built with lots of external libs.

  


  Are external libs creating the difference or my built ffmpeg application is not right ? Do I need all those libs in my application too in order to get similar output ?

  


  screenshot output.mp4 from built ffmpeg.exe(15 Mb)