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• Convert Transparent PNGs to a Transparent Video

  15 février 2023, par Aurora7979

  I have a set of transparent PNG pictures, and I want to convert them into a video with transparent background (play the PNGs continuously).

  


  First, I used ffmpeg with the terminal command :

  


  ffmpeg -framerate 30 -pattern_type glob -i '*.png' \-c:v libx264 -pix_fmt yuva420p out.mp4


  


  And I learnt that the codec libx264 does not compatible with the alpha channel. Then, I changed to another codec and used the following command :

  


  ffmpeg -framerate 30 -pattern_type glob -i '*.png' \-c:v libvpx-vp9 -pix_fmt yuva420p out.mp4


  


  However, QuickTime Player cannot play the resulting out.mp4. I don't know if it was because the video conversion failed or it was the fault of QuickTime Player. The terminal didn't show any error message, though.

  


  Therefore, I would like to ask :

  


  


  1. Which codec I should use to create a transparent video that a normal video player can play ?

     


  


  2. Can the output MP4 video format support transparent videos ?

     


  


  3. If there is another tool that is far more superior than ffmpeg for my purpose, I am willing to give it a try.

     


  


  


  Thank you for any advice.

  


  All the best,

  


  Aurora

  


• Preserving original colour spaces with FFmpeg

  12 décembre 2022, par Hashim Aziz

  I'm trying to implement some logic in my FFmpeg scripts to make sure that a video's colourspace is always preserved when upscaling. Just setting the metadata seems to be enough to do this, but the hard part is figuring out which metadata is needed, especially when the colourspace and related colour data reads as unknown, as is so often the case with many of my source videos.

  


  As I understand it, two things determine a video's original colourspace : whether a video is standard or high definition, and if it's standard definition, whether it's NTSC or PAL/SECAM. Based on this, I came up with the following logic to check the height of a video and set colourspace according to it :

  


  height=$(ffprobe -v error -select_streams v:0 -show_entries stream=width -of default=nw=1:nk=1 "$1" | tr -d $'\r')
colour_space=$(ffprobe -v error -select_streams v:0 -show_entries stream=color_space -of default=nw=1:nk=1 "$1" | tr -d $'\r')

# If input is standard definition and colourspace is BT601 (NTSC)
if [[ $height -lt 720 && $colour_space == "smpte170m" ]]; then 
colour_metadata="-colorspace smpte170m -color_trc smpte170m -color_primaries smpte170m" # set metadata to BT601 (NTSC)
# If input is standard definition and colourspace is BT601 (PAL and SECAM) or unknown
elif [[ $height -lt 720 && ($colour_space == "bt470bg" || $colour_space == "unknown") ]]; then 
colour_metadata="-colorspace bt470bg -color_trc gamma28 -color_primaries bt470bg" # set metadata to superior/more common PAL/SECAM
elif [[ $height -ge 720 ]]; then # If input is high definition
colour_metadata="-colorspace bt709 -color_trc bt709 -color_primaries bt709" # set metadata to BT.709
else echo "Unrecognised colorspace $color_space detected, leaving colour untouched"
fi


  


  Is this approach likely to work for the majority of videos ? Is there anything wrong with it that can be improved, or is it completely flawed for some reason that I'm missing ?

  


• avutil/fifo : Deprecate old FIFO API

  30 décembre 2021, par Anton Khirnov

  avutil/fifo : Deprecate old FIFO API
  Users should switch to the superior AVFifo API.
  Unfortunately AVFifoBuffer fields cannot be marked as deprecated because
  
  it would trigger a warning wherever fifo.h is #included, due to
  
  inlined av_fifo_peek2().
  

  • [DH] doc/APIchanges
  • [DH] libavutil/fifo.c
  • [DH] libavutil/fifo.h
  • [DH] libavutil/version.h