Answers.Body: <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>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-10-20T13:53:56.277Z
Answers.LastActivityDate: 2020-10-20T14:04:12.243Z
Answers.LastEditDate: 2020-10-20T14:04:12.243Z
Answers.UserDisplayName: xer-rex
Body: <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>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-10-20T04:23:05.190Z
Comments.Text: Share full log.
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-10-20T13:50:43.173Z
Comments.Text: May i know the reason of using the option -pix_fmt yuva420p ?
Comments.UserDisplayName: xer-rex
Tags: <ffmpeg><transcoding>
Title: ffmpeg conversion - vp8 with alpha
UserDisplayName: javier41
ThreadText: # 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 ?  
  
  ---
  
  ## 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.
  
  
  ---
  
  