Bug 241220

Created attachment 459955 [details]
fx-rt-profiler-part-a.webm

STR:
- Open the attached file in current Safari (Version 15.4 17613.1.17.1.6) or Safari Technology Preview (Release 146, Safari 15.4, WebKit 17614.1.14.10.6). It's also live on a page at https://blog.paul.cx/post/profiling-firefox-real-time-media-workloads/#the-new-solution

Expected:
- It plays

Actual:
- It doesn't play. The console reports: "Failed to load resource: PLugin-in handled load".
- I can reproduce this on both an x86_64 and ARM MacBook Pro running Monterey 12.3.
- Firefox, Chrome and all native media players that I've tested play the file


ffprobe on the file:

> Input #0, matroska,webm, from 'fx-rt-profiler-part-a.webm':
>   Metadata:
>     COM.APPLE.QUICKTIME.SOFTWARE: Mac OS X 10.15.5 (19F101)
>     MAJOR_BRAND     : qt  
>     MINOR_VERSION   : 0
>     COMPATIBLE_BRANDS: qt  
>     COM.APPLE.QUICKTIME.CREATIONDATE: 2020-06-17T15:09:11+0200
>     COM.APPLE.QUICKTIME.MAKE: Apple
>     COM.APPLE.QUICKTIME.MODEL: MacBookPro15,1
>     ENCODER         : Lavf58.20.100
>   Duration: 00:00:38.57, start: -0.007000, bitrate: 659 kb/s
>   Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1980x1212, SAR 1:1 DAR 165:101, 60 fps, 60 tbr, 1k tbn, 1k tbc (default)
>     Metadata:
>       HANDLER_NAME    : Core Media Video
>       ENCODER         : Lavc58.35.100 libvpx-vp9
>       DURATION        : 00:00:38.557000000
>   Stream #0:1: Audio: opus, 48000 Hz, 7.1, fltp (default)
>     Metadata:
>       HANDLER_NAME    : Core Media Audio
>       ENCODER         : Lavc58.35.100 libopus
>       DURATION        : 00:00:38.573000000