Answers.Body: <p>create videos with different resolutions:</p>
  <pre><code>ffmpeg -lavfi &quot;color=green:704x396;anullsrc&quot; -t 1 &quot;in-01.webm&quot; -y
  ffmpeg -lavfi &quot;color=yellow:640x480;anullsrc&quot; -t 1 &quot;in-02.webm&quot; -y
  ffmpeg -lavfi &quot;color=red:800x450;anullsrc&quot; -t 1 &quot;in-03.webm&quot; -y
  </code></pre>
  <p>and concat:</p>
  <pre><code>echo &quot;file 'in-01.webm'&quot; &gt; list.txt
  echo &quot;file 'in-02.webm'&quot; &gt;&gt; list.txt
  echo &quot;file 'in-03.webm'&quot; &gt;&gt; list.txt
  
  ffmpeg -f concat -safe 0 -i &quot;list.txt&quot; -c copy output.webm -y
  
  mpv output.webm
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-03-12T07:01:50.890Z
Answers.LastActivityDate: 2023-03-12T07:01:50.890Z
Answers.UserDisplayName: Баяр Гончикжапов
Body: <p>I found a video posted on discord once that made the whole webpage underneath it bounce up and down when it was played. I assume it must have been encoded using a codec that supports a variable resolution, so the y frame height got shorter and longer to make the whole page bounce. I downloaded the video and these are the details:</p>
  <p><a href="https://i.sstatic.net/DRFeP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/DRFeP.png" alt="enter image description here" /></a></p>
  <p>It appears to be a WebM file. I don't understand how it would have been encoded using a variable resolution though. Any ideas how to do this? Can ffmpeg encode a PNG sequence with variable resolutions for each frame into a single video that also has variable resolution?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-03-11T05:06:41.777Z
Comments.Text: concat demuxer http://ffmpeg.org/ffmpeg-all.html#concat-1
Comments.UserDisplayName: Баяр Гончикжапов
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-03-11T16:14:39.830Z
Comments.Text: @БаярГончикжапов, I'm sorry, I'm not quite following. Could you provide an example?
Comments.UserDisplayName: EllipticalInitial
Tags: <ffmpeg>
Title: Codecs supporting variable resolution (y height of frame changes with time)?
UserDisplayName: EllipticalInitial
ThreadText: # Codecs supporting variable resolution (y height of frame changes with time)?
  
  (Asked by: username_0 on 2023-03-10)
  
  I found a video posted on discord once that made the whole webpage underneath it bounce up and down when it was played. I assume it must have been encoded using a codec that supports a variable resolution, so the y frame height got shorter and longer to make the whole page bounce. I downloaded the video and these are the details:
  
  [![enter image description here](https://i.sstatic.net/DRFeP.png)](https://i.sstatic.net/DRFeP.png)
  
  It appears to be a WebM file. I don't understand how it would have been encoded using a variable resolution though. Any ideas how to do this? Can ffmpeg encode a PNG sequence with variable resolutions for each frame into a single video that also has variable resolution?
  
  **Tags:** ffmpeg
  
  > **Comments:**
  > **username_1**: concat demuxer http://ffmpeg.org/ffmpeg-all.html#concat-1  
  > **username_0**: @username_1, I'm sorry, I'm not quite following. Could you provide an example?  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2023-03-12. Score: 1
  
  create videos with different resolutions:
  
  ```
  ffmpeg -lavfi "color=green:704x396;anullsrc" -t 1 "in-01.webm" -y
  ffmpeg -lavfi "color=yellow:640x480;anullsrc" -t 1 "in-02.webm" -y
  ffmpeg -lavfi "color=red:800x450;anullsrc" -t 1 "in-03.webm" -y
  
  ```
  
  and concat:
  
  ```
  echo "file 'in-01.webm'" > list.txt
  echo "file 'in-02.webm'" >> list.txt
  echo "file 'in-03.webm'" >> list.txt
  
  ffmpeg -f concat -safe 0 -i "list.txt" -c copy output.webm -y
  
  mpv output.webm
  
  ```
  
  
  ---
  
  