<p>The zoompan size parameter cannot be animated. It has to be a fixed numeral size of the form WxH, or a <a href="https://ffmpeg.org/ffmpeg-utils.html#Video-size" rel="nofollow noreferrer">size label</a> like hd1080.</p>

CC BY-SA 4.0
2019-03-24T07:22:40.280Z
Thank You again, Gyan!
I was hoping to achieve less than 100% zoom without padding by tweaking output size )
Serge
CC BY-SA 4.0
2019-03-24T07:14:07.500Z
2019-03-24T07:14:07.500Z
Gyan
<p>How is it possible to dynamically evaluate the <code>s</code> (output image size) parameter of ffmpeg <a href="https://ffmpeg.org/ffmpeg-filters.html#zoompan" rel="nofollow noreferrer">zoompan</a> filter on each frame?</p>

<p>The parameter expectes its value in "WxH" format i.e. "1920x1080". 
How to substitute an expression that would update the size as a function of, say, frame number?</p>

<p>Couldn't find a way to concatenate strings.</p>

<p>For a single number parameter I can do smth like <code>y='(out_h-in_h)/2'</code>, but how to take two expressions and join them with an "x" string?</p>

<ffmpeg>
How to animate size parameter of ffmpeg zoompan filter?
Serge
# How to animate size parameter of ffmpeg zoompan filter?

(Asked by: username_0 on 2019-03-24)

How is it possible to dynamically evaluate the `s` (output image size) parameter of ffmpeg [zoompan](https://ffmpeg.org/ffmpeg-filters.html#zoompan) filter on each frame?

The parameter expectes its value in "WxH" format i.e. "1920x1080".
How to substitute an expression that would update the size as a function of, say, frame number?

Couldn't find a way to concatenate strings.

For a single number parameter I can do smth like `y='(out_h-in_h)/2'`, but how to take two expressions and join them with an "x" string?

**Tags:** ffmpeg


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## 1 answers

### Answer by username_1 on 2019-03-24. Score: 1 | Accepted answer

The zoompan size parameter cannot be animated. It has to be a fixed numeral size of the form WxH, or a [size label](https://ffmpeg.org/ffmpeg-utils.html#Video-size) like hd1080.

> **Comments:**
> **username_0**: Thank You again, username_1! I was hoping to achieve less than 100% zoom without padding by tweaking output size )  

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