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• How can I use FFMPEG to extract a specific color from a video and put it over alpha ?

  28 février 2024, par Michael Macha

  I have a rendered animation which looks great, but my original file was not saved properly and has lost some of the data. I can quickly get that data back, if I can extract a specific color from the rendered video to a new file or image sequence, over either a key color or preferably transparency.

  


  Since I'm hand animating this, it's important that I automate as much as possible. I think FFMPEG could come to the rescue here and help me retrieve that data.

  


  My current line is this :

  


  ffmpeg -i ./"Light Bleeder Twirl Above.mp4" -vf "colorkey=0xe1eff9:0.1:0.1,format=rgba" -c:a copy ./out%04d.png


  


  Here, E1EFF9 is the color I'm after. It successfully extracts the handful of frames to PNG files, but it copies all of the data, not just E1EFF9.

  


  I'm not sure why colorkey isn't doing what I want it to. If someone could provide some insight, it would be much appreciated.

  


  Addendum : So, my idea worked in principle ; I did a chroma key with Kdenlive and color-to-alpha'd the black to transparency after a manual rescale. It isn't exactly the same, but it's very close and saves a lot of time. I still feel like it should most certainly have worked with FFMPEG, much faster, and would still like to know what was wrong with my script.

  


• aarch64 : Manually tweak vertical alignment/indentation in tx_float_neon.S

  17 octobre 2023, par Martin Storsjö

  aarch64 : Manually tweak vertical alignment/indentation in tx_float_neon.S
  Favour left aligned columns over right aligned columns.
  In principle either style should be ok, but some of the cases
  
  easily lead to incorrect indentation in the surrounding code (see
  
  a couple of cases fixed up in the preceding patch), and show up in
  
  automatic indentation correction attempts.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/aarch64/tx_float_neon.S

• Multimedia Exploration Journal : The Past Doesn’t Die

  12 juillet 2011, par Multimedia Mike — Game Hacking

  New haul of games, new (old) multimedia formats.

  Lords of Midnight
  Check out the box copy scan for Lords of Midnight in MobyGames. In particular, I’d like to call your attention to this little blurb :

  
  
  

  Ahem, "Journey through an immense world — the equivalent of 8 CD-ROMs." Yet, when I procured the game, it only came on a single CD-ROM. It’s definitely a CD-ROM (says so on the disc) and, coming from 1995, certainly predates the earliest DVD-ROMs (which can easily store 8 CD-ROMs on a disc). Thus, I wanted to jump in a see if they were using some phenomenal compression in order to squeeze so much info into 600 or so megabytes.

  I was surprised to see the contents of the disc clocking in at just under 40 megabytes. An intro movie and an outro movie account for 75% of that. Format ? None other than that curious ASCII anomaly, ARMovie/RPL with Escape 122 codec data.

  Cyclemania

  
  
  

  Cyclemania is one of those FMV backdrop action games, but with a motorcycle theme. I had a good feeling I would find some odd multimedia artifacts here and the game didn’t disappoint. The videos are apparently handled using 3-4 discrete files per animation. I’ve documented my cursory guesses and linked some samples at the new MultimediaWiki page.

  Interplay ACMP
  This is unrelated to this particular acquistion, but I was contacted today about audio files harvested from the 1993 DOS game Star Trek : Judgment Rites. The files begin with the ASCII signature "Interplay ACMP Data". This reminds me of Interplay MVE files which begin with the similar string "Interplay MVE File". My theory is that these files use the ACOMP compression format, though I’m still trying to make it fit.

  Wiki and samples are available as usual if you’d like to add your own research.