Animated Webp - change framerate

Question

Is there any tool or script for batch converting animated webp images?

I want to create animated thumbnails from my animated webp images:

• resize image size
• reduce quality (lossy compression)
• reduce frame rate

I tried tools like ImageMagick, but they cannot change the frame rate.

Answer 1

If you just want to change the framerate, the webpmux tool from Google (available as the webp package on your Linux OS) can do the job quickly and easily.

First you need to know the current duration interval for the source file - there are several ways to do that, but the webpinfo from the same package is maybe the easiest - webpinfo source.webp the note the duration listed for the frames.

Then calculate your new desired frame rate - if the source animation had an FPS of 10, it would show a duration of 100. To change it to 25, divide 100ms duration by 2.5 (the multiplier to go from 10 to 25), which will get you a target duration of 40ms.

Finally run webpmux -duration 40 source.webp -o destination.webp to create a copy of the source animation with a changed interhframe duration.

Answer 2

ffmpeg can't decode animated WebP

See #4907: Support decoding animated WebP images.

Use another tool, such as anim_dump, to extract the WebP frames. See How can I convert an animated WebP to a WebM? for more info and examples.

Once you have the frames you can use ffmpeg.

Example

10 fps, half size:

ffmpeg -framerate 25 -i input_%03d.webp -vf "fps=10,scale=iw/2:-1" -quality 25 output.webp

To encode WebP, ffmpeg must be compiled with --enable-libwebp.

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resize image size

Use the scale filter.

reduce quality (lossy compression)

• Use the -quality option for the encoder libwebp. Range is 0-100. Default is 75.
• Optionally, use the -preset option to match the content type.

See ffmpeg -h encoder=libwebp for more options and info.

reduce frame rate

Use the fps filter or the -r option.