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• avcodec/hevcdec : apply H.274 film grain

  29 septembre 2021, par Niklas Haas

  avcodec/hevcdec : apply H.274 film grain
  Similar in spirit and design to 66845cffc3bbb, but slightly simpler due
  
  to the lack of interlaced frames in HEVC. See that commit for more
  
  details.
  For the seed value, since no specification for this appears to exist, I
  
  semi-arbitrarily decided to base it off the POC id alone, since there's
  
  no analog of the idr_pic_id in HEVC's I-frames. This design is stable
  
  across remuxes and seeks, but changes for adjacent frames with a period
  
  that's typically long enough not to be noticeable, which makes it
  
  satisfy all of the requirements that a film grain seed should have.
  Tested with and without threading, using a patch to insert film grain
  
  metadata artificially (for lack of real files containing film grain).
  

  • [DH] libavcodec/hevc_refs.c
  • [DH] libavcodec/hevcdec.c
  • [DH] libavcodec/hevcdec.h

• Convert DTS to AC3 but only if there is no AC3 track already present in container

  24 mars, par Domagoj

  I have sound system that does not support DTS only AC3. I'm automating the process using bash that detects when movie was added to folder, downloads subtitles and converts audio track to AC3 using this command (one part of it) :

  


  ffmpeg -i "{{episode}}" -map 0:v -map 0:a:0 -map 0:a -map 0:s -c:v copy -c:a copy -c:s copy -c:a:0 ac3 -b:a:0 640k "{{directory}}"/{{episode_name}}temp2.mkv

  


  This works without issue and I end up with a .mkv file that contains original DTS audio track and newly created AC3 audio track. The issue is that some files already contain both AC3 and DTS tracks and in those cases I end up with two AC3 tracks and one DTS track. Another issue is that this command is triggered every time there is update to subtitles. So it's possible that the command will execute multiple times in a period of a few days and the container will have X number of the AC3 tracks.

  


  I need a way to detect if file already contains AC3 track before I initiate command from above, but I'm not sure what the command would be. Any help is appreciated !

  


• AWS Lambda tmp memory limit with ffmpeg

  19 avril 2022, par Almaju

  I am using AWS Lambda to render videos using ffmpeg. It is a basic function that downloads external clips, merges those, then uploads the result to S3.

  


  This function needs to be able to scale quickly because I need to generate a lot of videos in a short time period.

  


  The problem is that I reach the /tmp disk limit of 512MB because the same lambda environment is reused by the different requests. I have increased that memory limit to temporarily solve the problem but it does not feel scalable.

  


  I have looked into EFS but the requirement to use a VPC and a NAT to have internet access sounds really heavy for my simple needs.

  


  Is there a way to output the result of ffmpeg directly in S3 (thus not needing the temporary folder) ? Or perhaps force to respawn a clean lambda environment if the memory is about to be full ?