<p>Documentation for ffmpeg is at <a href="http://www.ffmpeg.org/documentation.html" rel="nofollow noreferrer">http://www.ffmpeg.org/documentation.html</a></p>
<p><code>scale</code> here refers to the scale filter, whose documentation is at <a href="http://www.ffmpeg.org/ffmpeg-filters.html#scale-1" rel="nofollow noreferrer">http://www.ffmpeg.org/ffmpeg-filters.html#scale-1</a></p>
<p>The list of variables available in this filter is listed at the bottom of the <a href="http://www.ffmpeg.org/ffmpeg-filters.html#Options-1" rel="nofollow noreferrer">Options</a> section.</p>

CC BY-SA 4.0
2021-06-14T09:58:24.190Z
I did try the documentation, but it was difficult to find the values. Are the values for scaling the only variables of this kind?  I was hoping for one that would give the frame rate of the video being read, or the bit rates of the video and audio of the file being read.
Bart Lederman
CC BY-SA 4.0
2021-06-14T14:59:33.100Z
The variables available in a filter are specific to it. By convention, filters will use similar names for a parameter. But you need to consult an filter's doc for that info.
Gyan
CC BY-SA 4.0
2021-06-13T17:37:34.787Z
2021-06-13T17:37:34.787Z
Gyan
<p>There is an article that says you can scale a video to be a multiple or fraction of the input size like this:</p>
<pre><code>-vf &quot;scale=iw/2:ih/2&quot; to scale by half
</code></pre>
<p>Are there any other symbols for input variables in addition to <code>iw</code> and <code>ih</code>?</p>
<p>I've done multiple web searches and forum searches and I can't find anything that says what list of input values there are that are like <code>ih</code> and <code>iw</code>.</p>
<p>Thanks.</p>

CC BY-SA 4.0
2021-06-16T08:16:17.423Z
Welcome to Video Production! [What should I do when someone answers my question?](https://video.stackexchange.com/help/someone-answers)
MarianD
<ffmpeg>
Is there a list of input variables?
Bart Lederman
# Is there a list of input variables?

(Asked by: username_0 on 2021-06-13)

There is an article that says you can scale a video to be a multiple or fraction of the input size like this:
-vf "scale=iw/2:ih/2" to scale by half

Are there any other symbols for input variables in addition to iw and ih?
I've done multiple web searches and forum searches and I can't find anything that says what list of input values there are that are like ih and iw.
Thanks.

**Tags:** ffmpeg

> **Comments:**
> **username_1**: Welcome to Video Production! [What should I do when someone answers my question?](https://video.stackexchange.com/help/someone-answers)  

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## 1 answers

### Answer by username_2 on 2021-06-13. Score: 1

Documentation for ffmpeg is at <http://www.ffmpeg.org/documentation.html>

`scale` here refers to the scale filter, whose documentation is at <http://www.ffmpeg.org/ffmpeg-filters.html#scale-1>

The list of variables available in this filter is listed at the bottom of the [Options](http://www.ffmpeg.org/ffmpeg-filters.html#Options-1) section.

> **Comments:**
> **username_0**: I did try the documentation, but it was difficult to find the values. Are the values for scaling the only variables of this kind?  I was hoping for one that would give the frame rate of the video being read, or the bit rates of the video and audio of the file being read.  
> **username_2**: The variables available in a filter are specific to it. By convention, filters will use similar names for a parameter. But you need to consult an filter's doc for that info.  

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