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• aarch64 : Update the var2 functions to the new signature

  29 mai 2017, par Martin Storsjö

  aarch64 : Update the var2 functions to the new signature
  The existing functions could easily be used by just calling them
  
  twice - this would give the following cycle numbers from checkasm :
  var2_8x8_c :      4110
  
  var2_8x8_neon :   1505
  
  var2_8x16_c :     8019
  
  var2_8x16_neon :  2545
  However, by merging both passes into the same function, we get the
  
  following speedup :
  
  var2_8x8_neon :   1205
  
  var2_8x16_neon :  2327
  

  • [DH] common/aarch64/pixel-a.S
  • [DH] common/aarch64/pixel.h
  • [DH] common/pixel.c

• MLT melt slideshow on Windows : unable to control output video length and problems with using wildcards

  10 novembre 2020, par Tjk

  I am using the following command within a batch script to, hopefully, eventually programmatically create simple video slideshows with transitions :

  


  melt 131.jpg 132.jpg 133.jpg ttl=75 -attach crop center=1 -filter luma cycle=75 duration=25 -transition mix -consumer avformat:out.mp4 frame_rate_num=30 frame_rate_den=1


  


  Most of this command is an adaptation for Windows of this command on the MLT website blog (with the exception of the part that scales and transforms the image). For some reason when I run this, however, the output video file is 25 minutes long !

  


  I have two main questions :

  


  a. How do I properly control the duration of each image in the video ? I have experimented quite a bit with changing the parameters and I have a semi-decent understanding of what they all mean (I am a newbie to MLT but I figured that there's no way to do something like this easily in FFMPEG alone). The only way I have found to decrease the duration with any amount of control is to increase the output framerate to absurd numbers (which, of course, is not ideal as it's a massive waste of time and energy and still doesn't really solve the issue).

  


  b. How do I use a wildcard to input all the .jpg files in a folder on Windows ? I tried adding *.jpg but that didn't work and I don't know how else to do it within a batch script (I tried using the following code to get the file names as a variable, but I wasn't able to get string concatenation working correctly because it only outputs the final file name)

  


  set files=
for /r %%i in (*.jpg) do (
    echo %%i
    set files=%files% "%%i"
)
echo %files%


  


  Thank you for any suggestions !

  


• ffmpeg : How to replace a series of frames with a series of image files ?

  14 septembre 2020, par Arnon Weinberg

  Given a video file, start and end timestamps, there is a known number of frames between those timestamps in the video file, and I have an equal number of .png files in a directory to replace them with. The .png files are sorted as 001.png ... NNN.png. How would I go about updating the video file with the replacement frames using ffmpeg ?

  


  This is a followup to using ffmpeg to replace a single frame based on timestamp, but I'm asking about replacing multiple sequential frames based on 2 timestamps.

  


  Presumably something like :

  


  ffmpeg -i input.mp4 -i %3d.png -filter_complex "something including the timestamps 4.40,5.20" -c:a copy output.mp4


  


  I would also be okay with using frame numbers instead of timestamps if that makes things easier, and it's reasonable if start and end frames must be keyframes.

  


  Background :

  


  Many machine learning algorithms for video processing use ffmpeg to extract specific scenes from videos based on start and end timestamps, dump them into a sequence of .png files, process them in some way (denoise, deblur, colorize, annotate, inpainting, etc), and output the results into an equal number of .png files. The output frames are usually assembled into a new video file, but I would like instead to update the source video file so as to preserve audio, unedited video, and other video properties (fps, keyframes, etc).

  


  This approach will not work as-is for some categories of video processing algorithms. For example, interpolation results in more frames than were originally extracted, and upscaling results in higher-resolution images. As such, I would appreciate an explanation of any solution so that I can adapt it for such cases (or I will ask separate questions for those).