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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 :)

  


• AWS Lambda making video thumbnails

  5 février 2017, par Jesus

  I want make thumbnails from videos uploaded to S3, I know how to make it with Node.js and ffmpeg.

  According to this forum post I can add libraries :

  ImageMagick is the only external library that is currently provided by
  default, but you can include any additional dependencies in the zip
  file you provide when you create a Lambda function. Note that if this
  is a native library or executable, you will need to ensure that it
  runs on Amazon Linux.

  But how can I put static ffmpeg binary on aws lambda ?

  And how can I call from Node.js this static binary (ffmpeg) with AWS Lambda ?

  I’m newbie with amazon AWS and Linux

  Can anyone help me ?