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• Web-based video editor

  13 avril 2021, par Danny

  We have a web-based editor currently that allows users to build animated web apps. The apps are made up of shapes, text, images, and videos. Except for videos, all other elements can also be animated around the screen. The result of building a animated app is basically a big blob of JSON.

  



  The playback code for the web app is web-based as well. It takes the JSON blob and constructs the HTML, which ends up playing back in some sort of browser environment. The problem is that most of the time this playback occurs on lower-end hardware like televisions and set-top boxes.

  



  These performance issues go away if there is some way to be able to convert a digital sign to video. Then the STB/smart TV simply plays a video, which is much more performant than playing back animations in a web view.

  



  Given a blob of JSON describing each layer and how to draw each type of object, its animation points, etc, how could I somehow take that and convert it to video on the server ?

  



  My first attempt at this was using PhantomJS to load the playback page in a headless browser, take a series of screenshots, and then use ffmpeg to merge those screenshots into a video. That worked great so long as there is no video. But it does not work with video since there is no HTML5 video tag support in PhantomJS, and even if there was, I would lose any audio.

  



  The other way I was thinking of doing it would be to again load the playback page in PhantomJS, but turn off the video layers and leave them transparent, then take screenshots as a series of PNGs with transparency. I would then combine these with the video layers.

  



  None of this feels very elegant though. I know there are web-based video editors out there that basically do what I'm trying to accomplish, so how do they do it ?

  


• avcodec/xbmenc : substitute end instead of recalculating end

  1er février 2021, par Jose Da Silva

  avcodec/xbmenc : substitute end instead of recalculating end
  Minor speed increase, end is calculated before entering parse_str_int(),
  
  so let's take advantage of the value and avoid recalculating twice more.
  
  This also allows parse_str_int() to work with file size larger than int.
  Signed-off-by : Joe Da Silva <digital@joescat.com>
  

  • [DH] libavcodec/xbmdec.c

• avcodec/xbmenc : Pre-compute variables once for parse_str_int()

  1er février 2021, par Jose Da Silva

  avcodec/xbmenc : Pre-compute variables once for parse_str_int()
  Some compilers are very intuitive, and others are not so much, so let's
  
  pre-compute the variables e and keylen outside the for loop. Ensuring a
  
  minor speed increase regardless of if compiler is smart enough to solve
  
  this improvement for itself, or not.
  Signed-off-by : Joe Da Silva <digital@joescat.com>
  

  • [DH] libavcodec/xbmdec.c