<p>I took the sample from apple <a href="https://developer.apple.com/videos/play/wwdc2019/506/" rel="nofollow noreferrer">https://developer.apple.com/videos/play/wwdc2019/506/</a></p>
<p>My command line using on colab was</p>
<pre><code>!ffmpeg -y -i https://devstreaming-cdn.apple.com/videos/wwdc/2019/506lqy7sprpfyo800/506/506_hd_hevc_video_with_alpha.mp4 -s 960x540 -vcodec vp8 -metadata:s:v:0 alpha_mode=&quot;1&quot; c0016_alpha.webm
</code></pre>
<p>Hope it matches your scenario.</p>

CC BY-SA 4.0
2020-10-20T13:53:56.277Z
2020-10-20T14:04:12.243Z
2020-10-20T14:04:12.243Z
xer-rex
<p>I'm trying to convert a mov file (with alpha channel) to webm, vp8 with alpha, on windows.</p>
<p><code>ffmpeg -i C0016.mov -s 960x540 -vcodec vp8 -pix_fmt yuva420p -metadata:s:v:0 alpha_mode=&quot;1&quot; c0016_alpha.webm​</code></p>
<p>gives me:</p>
<p>[NULL @ 00000204af221e80] Unable to find a suitable output format for 'c0016_alpha.webm​'
c0016_alpha.webm​: Invalid argument</p>
<p>How can I fix it?</p>

CC BY-SA 4.0
2020-10-20T04:23:05.190Z
Share full log.
Gyan
CC BY-SA 4.0
2020-10-20T13:50:43.173Z
May i know the reason of using the option -pix_fmt yuva420p ?
xer-rex
<ffmpeg><transcoding>
ffmpeg conversion - vp8 with alpha
javier41
# ffmpeg conversion - vp8 with alpha

(Asked by: username_0 on 2020-10-19)

I'm trying to convert a mov file (with alpha channel) to webm, vp8 with alpha, on windows.

`ffmpeg -i C0016.mov -s 960x540 -vcodec vp8 -pix_fmt yuva420p -metadata:s:v:0 alpha_mode="1" c0016_alpha.webm​`

gives me:

[NULL @ 00000204af221e80] Unable to find a suitable output format for 'c0016\_alpha.webm​'
c0016\_alpha.webm​: Invalid argument

How can I fix it?

**Tags:** ffmpeg, transcoding

> **Comments:**
> **username_1**: Share full log.  
> **username_2**: May i know the reason of using the option -pix_fmt yuva420p ?  

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## 1 answers

### Answer by username_2 on 2020-10-20. Score: 0

I took the sample from apple https://developer.apple.com/videos/play/wwdc2019/506/
My command line using on colab was
!ffmpeg -y -i https://devstreaming-cdn.apple.com/videos/wwdc/2019/506lqy7sprpfyo800/506/506_hd_hevc_video_with_alpha.mp4 -s 960x540 -vcodec vp8 -metadata:s:v:0 alpha_mode="1" c0016_alpha.webm

Hope it matches your scenario.


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