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• how the packuswb instruction works ? (in low level bit operation)

  17 avril 2019, par MaikonNascimento

  Studying ffmpeg convertion from yuv to rgb , I came across the equation being implemented in assembly, yuv2rgb_template.c located in ffmpeg/libswscale/x86.

  I want to know how the instruction packuswb works ? Google says it :

  Converts 4 signed word integers from mm and 4 signed word integers from mm/m64 into 8 unsigned byte integers in mm using unsigned saturation.

      DEST[7:0] ← SaturateSignedWordToUnsignedByte DEST[15:0];
  
      DEST[15:8] ← SaturateSignedWordToUnsignedByte DEST[31:16];
  
      DEST[23:16] ← SaturateSignedWordToUnsignedByte DEST[47:32];
  
      DEST[31:24] ← SaturateSignedWordToUnsignedByte DEST[63:48];
  
      DEST[39:32] ← SaturateSignedWordToUnsignedByte SRC[15:0];
  
      DEST[47:40] ← SaturateSignedWordToUnsignedByte SRC[31:16];
  
      DEST[55:48] ← SaturateSignedWordToUnsignedByte SRC[47:32];
  
      DEST[63:56] ← SaturateSignedWordToUnsignedByte SRC[63:48];

  Since I dont know Assembly x86, it is even hard to simulate it or debug the current code.

  I want to know how they fit 16 bits in 8 bits ?

• Ffmpeg it's not setting the correct variable names and hence throwing Unable to choose format

  9 novembre 2024, par Miguel Arrieche

  I'm trying to automate the subtitle addition to a folder with some videos so I wrote the following script :

  


  forfiles /p "C:\Users\titos\Resilio_Sync\4K_Video_Downloader\videoprocess" /m *.mp4 /C "cmd /c set filename=@fname & ffmpeg -i @file -vf subtitles="C:\Users\titos\Resilio_Sync\4K_Video_Downloader\videoprocess\@fname.srt" -f mp4 "C:\Users\titos\Resilio_Sync\4K_Video_Downloader\donesubs\@fname_srt.mp4""


  


  However, the script is throwing me the following error for each video :

  


  [AVFormatContext @ 0000020c20220680] Unable to choose an output format for 'Der'; use a standard extension for the filename or specify the format manually.
[out#0 @ 0000020c20220580] Error initializing the muxer for Der: Invalid argument
Error opening output file Der.
Error opening output files: Invalid argument


  


  In this case, "Der" is the second word of the video's title (And it does the same with each video where it throws the error with the second word). So I think it might be due to the videos containing spaces and ffmpeg not parsing it correctly ? But why is the second word that it gets and not the first one in that case ? And more importantly, what could I do to fix this issue ?

  


  I've honestly found some other threads that discuss similar issues, but quite frankly I'm still too newbie to understand any of the answers in order to adapt it to my script lol. I appreciate your help, thanks a lot in advance :)

  


• FFMPEG : Images are being loaded wrong (They for some reason have a duration) [closed]

  25 mars 2021, par Bas950

  On my video I am adding multiple overlays, 1 that will always be shown (Overlay/overlay.png) and I got a progress bar in PNGs named 0 to the last frame num.

  


  I tried ffmpeg -i 6875126077795372290.mp4 -i Overlay/overlay.png -i Overlay/ProgressBar/%d.png -filter_complex "[0:v][1:v]overlay=0:0[bg];[bg][2]overlay=0:20" output.mp4 which @llogan sent me and it does it all, but strangely the video is now 6 seconds longer (from 11sec to 17sec).
  
It seems like when it loads the images it make it have a duration of 17seconds (see full log linked below).

  How should I solve this ? (I got this file information using ffprobe)
  
Full file information : https://pastebin.com/rxkK39h7
  
Full ffmpeg log : https://pastebin.com/CBiusbRE