Extract audio
ffmpeg -i $INPUT -vn -acodec copy $DIR/audio.aac

Extract Frames
ffmpeg -i $INPUT $DIR/$FILENAME\_%d.png

Apply Watermark to pngs.

ffmpeg  -i $DIR/trans_$FILENAME%d.png -c:v libx264 -profile:v baseline -crf 18 -pix_fmt yuv420p -movflags faststart $OUTPUT -i $DIR/audio.aac -c:a aac -b:a 128k