[wp-trac] [WordPress Trac] #64105: TinyMCE in classic editor does not support modern video formats

[WordPress Trac]

#64105: TinyMCE in classic editor does not support modern video formats
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 Reporter:  blackstar1991  |       Owner:  (none)
     Type:  defect (bug)   |      Status:  new
 Priority:  normal         |   Milestone:  Awaiting Review
Component:  General        |     Version:  6.8.3
 Severity:  normal         |  Resolution:
 Keywords:  needs-patch    |     Focuses:  ui, javascript
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Comment (by lakshyajeet):

 == Reproduction Report
 === Description
 This report validates whether the issue can be reproduced. The testing
 confirms that while `.webm` files now appear to function in the Classic
 Editor, `.avi` files remain unsupported for playback. However, the `.avi`
 failure is likely a browser-level limitation rather than a WordPress bug,
 as `.avi` is not a standard format for the HTML5 `<video>` tag across
 modern browsers.

 === Environment
 - WordPress: 7.1-alpha-62161-src
 - PHP: 8.3.30
 - Server: nginx/1.29.7
 - Database: mysqli (Server: 8.4.8 / Client: mysqlnd 8.3.30)
 - Browser: Chrome 146.0.0.0
 - OS: macOS
 - Theme: Twenty Twenty-Five 1.4
 - MU Plugins: None activated
 - Plugins:
   * Classic Editor 1.6.7

 === Actual Results
 1.  ✅ Partial Reproduction: While `.webm` files successfully upload and
 play back in both editors, `.avi` files fail to render a preview or play
 back in both the Block Editor and Classic Editor.
 2.  ❌ Observation: The `.avi` playback issue appears to be a browser
 compatibility constraint. Most modern browsers do not support the AVI
 container within the native `<video>` element, leading to the reported
 "unsupported" behavior regardless of the editor used.

 === Additional Notes
 - **WebM:** During testing, `.webm` files worked as expected in the
 Classic Editor, suggesting that recent updates may have already addressed
 the MIME type registration for this specific format.
 - **AVI:** Since the Block Editor also fails to play `.avi` files, this is
 not a TinyMCE-specific issue but a general limitation of web-standard
 video playback. WordPress successfully handles the file upload, but the
 browser cannot render the stream.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64105#comment:4>
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