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• avcodec/dovi_rpudec : implement limited DM decompression

  14 juillet 2024, par Niklas Haas

  avcodec/dovi_rpudec : implement limited DM decompression
  This implements the limited DM metadata compression scheme described in
  
  chapter 9 of the dolby vision bitstream specification.
  The spec is a bit unclear about how to handle the presence of static
  
  metadata inside compressed frames ; in that it doesn't explicitly forbid
  
  an encoder from repeating redundant metadata. In theory, we would need
  
  to detect this case and then strip the corresponding duplicate metadata
  
  from the existing set of static metadata. However, this is difficult to
  
  implement - esspecially for the case of metadata blocks which may be
  
  internally repeated (e.g. level 10).
  That said, the spec states outright that static metadata should be
  
  constant throughout the entire sequence, so a sane bitstream should not
  
  have any static metadata values changing from one frame to the next (at
  
  least up to a keyframe boundary), and therefore they should never be
  
  present in compressed frames. As a consequence, it makes sense to treat
  
  this as an error state regardless. (Ignoring them by default, or
  
  erroring if either AV_EF_EXPLODE or AV_EF_AGGRESSIVE are set)
  I was not able to find such samples in the wild (outside of artificially
  
  produced test cases for this exact scenario), so I don't think we need
  
  to worry about it until somebody produces one.
  

  • [DH] libavcodec/dovi_rpudec.c

• prores : Always assume limited range

  27 septembre 2017, par Vittorio Giovara

  prores : Always assume limited range
  As defined by the specification.
  

  • [DBH] libavcodec/proresdec.c

• Videos written with moviepy on amazon aws S3 are empty

  10 avril 2019, par cellistigs

  I am working on processing a dataset of large videos ( 100 GB) for a collaborative project. To make it easier to share data and results, I am keeping all videos remotely on an amazon S3 bucket, and processing it by mounting the bucket on an EC2 instance.

  One of the processing steps I am trying to do involves cropping the videos, and rewriting them into smaller segments. I am doing this with moviepy, splitting the video with the subclip method and calling :

  subclip.write_videofile("PathtoS3Bucket"+VideoName.split('.')[0]+'part' +str(segment)+ '.mp4',codec = 'mpeg4',bitrate = "1500k",threads = 2)

  I found that when the videos are too large (parameters set as above) calls to this function will sometimes generate empty files in my S3 bucket ( 10% of the time). Does anyone have insight into features of moviepy/ffmpeg/S3 that would lead to this ?