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• why reducing the resolution a percentage doesn't reduce the video the same proportion using ffmpeg ?

  14 mars 2023, par user44551

  I'm using this command :

  


  -y -r -i $inVideoUri -movflags faststart -c:v libx265 -s $videoResolution -c:a copy -preset ultrafast $outPutUri"


  


  However, if "videoResolution" is a 50% of the original video resolution, the resulting file size is not 50% of the original one. I assume there are some headers or metadata added during the process but I would like to know how to estimate the final video size.

  


• avcodec/h264_slice : don't sync default_ref[] between threads.

  18 juillet 2017, par Wan-Teh Chang

  avcodec/h264_slice : don't sync default_ref[] between threads.
  default_ref[] is unconditionally initialized in h264_initialise_ref_list()
  
  (called from ff_h264_build_ref_list(), called from h264_slice_init()).
  This fixes the following tsan warning when running fate-h264 :
  WARNING : ThreadSanitizer : data race (pid=31070)
  
    Write of size 8 at 0x7bbc000082a8 by thread T1 (mutexes : write M1628) :
  
      #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5
  
  (ffmpeg+0x10de9d)
  
      #1 h264_initialise_ref_list ffmpeg/libavcodec/h264_refs.c:214:29 (ffmpeg+0x1186b3f)
  
      #2 ff_h264_build_ref_list ffmpeg/libavcodec/h264_refs.c:306 (ffmpeg+0x1186b3f)
  
      #3 h264_slice_init ffmpeg/libavcodec/h264_slice.c:1900:11 (ffmpeg+0x1191149)
  
  [..]
  
    Previous read of size 8 at 0x7bbc000082a8 by main thread (mutexes :
  
  write M1630) :
  
      #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5
  
  (ffmpeg+0x10de9d)
  
      #1 ff_h264_update_thread_context ffmpeg/libavcodec/h264_slice.c:411:5 (ffmpeg+0x118b7dc)
  Signed-off-by : Wan-Teh Chang <wtc@google.com>
  
  Signed-off-by : Ronald S. Bultje <rsbultje@gmail.com>
  

  • [DH] libavcodec/h264_slice.c

• Extend plain background in a video

  3 juillet 2022, par Maiki

  Is there any easier way to achieve this ?, I'd like to make a .bat file that modify 148 videos that are 3840x2160

  


  They belong to the COLORFUL platform video set 1.8.0

  


  Every video has a system or console in the middle of it and it has a plain color as background. I want to keep the resolution, 3840x2160 but I need to displace the image a 15% to the right so it will be neccesary to fill the left area with the same color it's being use as color of the background.

  


  This is a snapshot from one of these videos :

  


  Snapshot of the original video

  


  The result should be something like this :

  


  Snapshot of the video I'd like to get

  


  So far I was trying lot of things with no success, I maybe did it harder than it is really. I did a first script that crop the video :

  


  for %%X in (*.mp4) do .\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -filter:v "crop=2688:ih" -c:a copy -threads 4 "second_script\%%X"


  


  The new video will be stored in the second_script folder, then there is a second script that will use ffmpeg to export a picture from the video and magick.exe will help me to identify the color, after that it will use ffmpeg again to add an are of that color, but ... for some reason I don't know the color result is not the same

  


  for %%X in (*.mp4) do (
..\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -vf "select=eq(n\,100)" -vframes 1 %%~nX.png

magick.exe .\%%~nX.png -format "%%[hex:u.p{0,0}]" info: > temp.txt

for /f "delims=" %%i in (temp.txt) do (
..\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -filter_complex "[0]pad = w=3840 : h=ih: x=3840-2688 : y=0 : color=#%%i" -movflags +faststart  -c:a copy -threads 4 "final\%%X"
)

)


  


  What I get is something like this :

  


  Final result, it doesn't look like I expected

  


  Would there be any easy way to do this ? any recommendation is really appreciate