[FFmpeg-user] How could I take advantage of HWACCLE support on Mac

[Zongyao Qu]

Recently, I found ffmpeg has merged some code
to support VideoDecodeAccelerate(vda), which is a 
framework on Mac OSX to support hardware-accelerated
decoding.

I have tried to compiled it, and confirmed it 
compiled into the binary.

But I dont know how to use it, 
I used ./ffmpeg -codecs but 
there is no entry of vda in the list.

and I tried to transcode some h264 file into other format,
it seams vda is not activated at all.

Does anyone could kindly tell me how I should 
use this decoder?

Thank you.