[MPlayer-dev-eng] Scaling in libvo

Kyle Mallory kyle.mallory at utah.edu
Wed Jun 5 22:20:30 CEST 2013

Hello devs,

I'm am writing a new libvo module that allows output to LED matricies 
based on the WS2801 driver (such as this: 
http://www.youtube.com/watch?v=ED2u5O7GyEY). My specific goals are to be 
able to display "electric sheep" directly to the matrix, through a 
Raspberry Pi.  I've done a bit of hacking on the old blinkenlights 
module, and have 95% working driver.

However, it was recently revealed to me that there is no effective weans 
to notify mplayer to scale the input video (to the vo module) to match 
the output device.

I realize that I can implement my own scaling inside of my driver, but 
it seems redundant particularly since mplayer is already using swscale 
to convert to IMGFMT _BGR24 (for the LED display).

What would be the most efficient way to scale the frame to my size? I 
know I can setup a swsContext and call the swscale library directly, but 
I wonder if its possible to make callbacks into the core of mplayer to 
tell it to scale before handing me the frame.

I'd prefer not to use -x and -y (and -zoom) if possible (that would 
require patching both electricsheep and mplayer).



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