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• Grey screen issue after recovered video with ffmpeg

  10 mars 2023, par Mark

  After recovered ".mp4" videos from mobile phone, some videos were corrupt. I used the FFMPEG method to fix the videos.
Some CMD commands below ;

  


  First Code: recover_mp4.exe good.mp4 --analyze

Second: recover_mp4.exe bad.mp4 recovered.h264 recovered.aac

Third: ffmpeg.exe -r 30 -i recovered.h264 -i recovered.aac -bsf:a aac_adtstoasc -c:v copy -c:a copy recovered.mp4

Alternate code: ffmpeg -i recovered.h264 -pix_fmt yuv420p -crf 18 result.mp4


  


  Some videos have been improved after using the above codes. Some videos work fine. On the other hand some videos work in video players, but images are only gray or green screen or a mix of both. In short, some videos do not work properly.

  


  Below I am sharing a screenshot from the video that is not working properly.

  


  greyscreenphotoexample

  


  Is it possible to fix the above errors ? Is there any other code or method I should use ? How can I handle the gray screen problems in the video ?

  


  Note : I have used all versions of FFMPEG and Recover_mp4.exe.

  


• configure : Don't pass -mfp16-format to MSVC on ARM

  21 décembre 2023, par Martin Storsjö

  configure : Don't pass -mfp16-format to MSVC on ARM
  The check for this option does succeed - MSVC accepts the option,
  
  but prints a warning about it being unknown and ignored, for
  
  each compiled object file :
      cl : Command line warning D9002 : ignoring unknown option '-mfp16-format=ieee'
  The configure script only attempts to add this option on ARM,
  
  therefore this warning isn't seen by the majority of people
  
  building with MSVC.
  Making this option into a no-op probably isn't entirely right,
  
  but on the other hand, we don't want to litter the code that
  
  checks for support for the option with compiler specific
  
  conditions either.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] configure

• FFMpeg image sequence to video using VP9 encoder [migrated]

  29 janvier 2016, par user778968

  I’m trying to transcode mp4 to webm format in a lossless way. I tried two ways to do that.

  For that purpose, I extracted mp4 video to image sequences (png). Then, I converted image sequence(without changing any frame) to webm video with a lossless flag. But, when i extract webm video to image sequences and compared with the images that i extracted from mp4 video, i realized that PSNR values were not infinity. It changes from between around 53-55 dB.

  On the other hand, I directly transcoded mp4 to webm with a lossless flag. Then, I extracted image sequences from mp4 and webm format and compared PSNR values. This time i realized that PSNR values are infinity.

  Encoding image sequences to webm video with lossless flag is not actually lossless. Is this true or am i doing something wrong ?