FFmpeg overlaying and blending videos

Question

I am trying to use FFmpeg to overlay one video on top of the other using an additive blend. One video is the actual video I want to transcode, the other is a ~10 second long video I want to put into one corner, sort of an animated watermark. The watermark video is some white animated stuff with a black background.

So far, I have tried something along these lines:

$ /d/ffmpeg/ffmpeg.exe -i actualvideo.mkv -i myoverlay.mp4 \
-filter_complex "[1:0] setsar=sar=1 [1sared]; [0:0][1sared] blend=all_mode='addition':repeatlast=1" \
test.mkv

The setsar seemed necessary as otherwise it would complain:

[Parsed_blend_0 @ 00000000043e0e40] First input link top parameters (size 1280x720, SAR 1:1) do not match the corresponding second input link bottom parameters (1280x720, SAR 0:1)

With the setsar there's no complaint, but the output video looks.. mostly pink. Both videos look fine when viewed on their own before I feed them into FFmpeg.

Any ideas? Am I doing something wrong?

Answer 1

I found a helpful post on stackoverflow that addresses this issue: https://stackoverflow.com/a/21400416/377875

Apparently, it's a problem with color space. Something like this works:

ffmpeg -i "$1" -i "$2" \
-filter_complex "[1:0] setsar=sar=1,format=rgba [1sared]; [0:0]format=rgba [0rgbd]; [0rgbd][1sared]blend=all_mode='addition':repeatlast=1:all_opacity=1,format=yuva422p10le" \
-c:v libx264 -preset slow -tune film -crf 19 \
-c:a aac -strict -2 -ac 2 -b:a 256k \
-pix_fmt yuv420p "$3"

(substitute $1 with your actual video, $2 with your overlay, and $3 with the output file name)