After having read this page, I'm using avconv (which in this case is apparently same as ffmpeg, and which I need to use instead since I'm on Ubuntu trusty) to speed up a .swf video.
I don't want a quality loss (not interested in compression), just a visual speed-up.
avconv -i input.swf -filter:v "setpts=0.5*PTS" output.swf
results in quality loss. how do I prevent that?
I don't see why this occurs,
mplayer -af scaletempo -speed 1.7 myvideo.swf plays it fine.
From reading this page I tried
avconv -i input.mkv -filter:v "setpts=0.5*PTS" -b 1080 output.mkv
But it didn't help.