How to use ffmpeg to make a video from one still image with height from 0 to 100% animation，

Question

I want use a still image to make a transparent webm video, this video needs to have the following style:

1. The image height auto increase from 0 to 100% in specific time.
2. I don't want scroll effect , what i want is just like the image spread from top to bottom

Below is my demo image:

This is the effect I want:

Black color part represent transparency.

Answer 1

_{1 second transition example}

ffmpeg command for 5 second transition:

ffmpeg -loop 1 -t 5 -i input.png -filter_complex "drawbox=thickness=fill:color=black[black];[black][0]xfade=transition=wipedown:duration=5" output.webm

• -loop 1 loops image.
• -t 5 sets image duration to 5 seconds.
• drawbox=thickness=fill:color=black drawbox filter to make black video from input.
• xfade=transition=wipedown:duration=5 xfade filter using wipedown transition with a duration of 5 seconds.

Also see:

• FFmpeg Wiki: xfade transitions gallery
• FFmpeg Wiki: VP9 WebM Encoding