[FFmpeg-user] Pixel format for sdl output device

[Michael Koch]

Hello,

in the following example I'm grabbing an equirectangular video from the 
desktop, convert it to 180° fisheye format and then use the sdl output 
device to show the output on a second monitor in realtime. It's working 
as expected but there is one thing I don't understand. At the end of the 
filter chain I had to insert "format=bgra". It doesn't work if I use 
rgb24 or bgrp or no format at all. Why does the sdl output device need a 
pixel format with alpha channel?

ffmpeg -f gdigrab -video_size 1920x1080 -i desktop -lavfi 
v360=e:fisheye:ih_fov=360:iv_fov=180:h_fov=180:v_fov=180:w=1080:h=1080,format=bgra 
-window_borderless 1 -window_x 2340 -window_y 0 -f sdl2 -

It's running with 20fps. Any ideas how to make it faster?

Michael