[Libav-user] AVFilter overlay transparent image onto another transparent image

Bryan Stewart bstewart at ais-sim.com
Mon May 14 20:18:06 CEST 2012

ffmpeg/libav version from git-1eabd71 windows build dated: 3/25/2012

I am trying to merge two transparent images onto one another using the 
avfilter overlay:

ffmpeg -i a.png -vf movie=a.png, transpose=1 [inA]; [in] [inA] overlay [out]

a.png has alpha in the image.

When I run, the main image is always converted to yuv420p (no alpha) 
while the overlay image remains a yuva420p image.  I have tried to 
insert the format filter in front, back, etc to the source image, but 
the filter graph still inserts an extra scale filter to force the main 
image to be a yuv420p (no alpha) image.

The resulting image always has the background as my image without alpha 
and the overlay image has alpha.

Is there a way to get the main overlay image to remain an alpha image?

#  Bryan C. Stewart                   Email: bstewart at ais-sim.com #
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