Firefox reports HEVC unsupported while Chrome can decode the same HEVC streams on the same system
(AI written summary of troubleshooting steps taken before making this support thread)
Firefox version: - 152.0.1 Release - 153.0 Nightly
OS: - Windows 11 build 26200
GPU: - NVIDIA GeForce RTX 4070 SUPER
Codec package: - Microsoft HEVC Video Extensions installed from Microsoft Store
Problem
Firefox does not expose HEVC playback support, causing Twitch to disable 1440p streams encoded with HEVC.
The same machine can play the same HEVC Twitch streams in Chrome immediately after installing HEVC Video Extensions.
Expected result
Firefox should report HEVC playback support and allow playback of HEVC streams, as Chrome does on the same system.
Actual result
Firefox reports HEVC as unsupported.
about:support:
codecSupportInfo: H264 SWDEC HWDEC VP9 SWDEC HWDEC VP8 SWDEC HWDEC AV1 SWDEC HWDEC HEVC NONE
Troubleshooting already performed
- Installed Microsoft HEVC Video Extensions - Rebooted Windows - Updated NVIDIA drivers - Verified hardware acceleration is enabled - Tested with a brand new Firefox profile - Tested with Firefox Nightly - Confirmed Chrome can play the same HEVC streams
Additional observations
Chrome: - Twitch 1440p becomes available immediately after installing HEVC Video Extensions - Twitch Stats for Nerds reports:
hev1.1.6.L150.90.0.0.0.0.0
Firefox: - Twitch reports that the browser does not support the required resolution - 1440p remains greyed out - about:support continues to report HEVC NONE
Reproducible tests
Firefox console:
MediaSource.isTypeSupported('video/mp4; codecs="hev1.1.6.L150.90"')
Result: false
MediaSource.isTypeSupported('video/mp4; codecs="hvc1.1.6.L150.90"')
Result: false
navigator.mediaCapabilities.decodingInfo({
type: "media-source",
video: {
contentType: 'video/mp4; codecs="hev1.1.6.L150.90"',
width: 2560,
height: 1440,
bitrate: 8000000,
framerate: 60
}
})
Result: {
supported: false, smooth: false, powerEfficient: false
}
For comparison:
MediaSource.isTypeSupported('video/mp4; codecs="av01.0.08M.08"')
Result: true
navigator.mediaCapabilities.decodingInfo({
type: "file",
video: {
contentType: 'video/mp4; codecs="av01.0.08M.08"',
width: 2560,
height: 1440,
bitrate: 8000000,
framerate: 60
}
})
Result: {
supported: true, smooth: true, powerEfficient: true
}
Additional note
Setting:
dom.media.webcodecs.h265.enabled = true
causes HTML5 codec test (https://html5test.co/) to report H.265 support, but does not change:
- about:support - MediaSource.isTypeSupported() - MediaCapabilities.decodingInfo() - Twitch HEVC playback availability
Question
Is this a known issue with HEVC Media Source Extensions support on Windows 11 build 26200, or is there another requirement for Firefox to expose HEVC playback capability through MediaSource and MediaCapabilities when the Windows HEVC codec is installed and functioning in Chromium-based browsers?
All Replies (3)
This is weird as bugzil.la/hevc-windows-support notes according to en.wikipedia.org/wiki/High_Efficiency_Video_Coding#:~:text=Notes%20%20,120 "Since Windows 11 version 22H2, the HEVC Video Extensions is built-in by default installation."
Firefox relies on the HEVC Video Extensions via the Windows Media Foundation. There's a note in https://codecguide.com/media_foundation_codecs.htm though:
"If you have a European N or Korean KN edition of Windows then you should also first install the Media Feature Pack from Microsoft to gain additional multimedia functionality. — You can recognize these special versions of Windows by the fact that they do no include Windows Media Player by default. — You can acquire this media package through Windows settings: Start > Settings > Apps > Apps & Features > Optional Features > Add a feature > Media Feature Pack"
Thanks. I checked and I'm not running an N or KN edition of Windows. I also tried installing the Media Feature Pack, but it did not change the behavior.
What confuses me is that Firefox appears to have working Media Foundation integration for other codecs:
H264 SWDEC HWDEC VP9 SWDEC HWDEC AV1 SWDEC HWDEC HEVC NONE
In addition, Chrome on the same machine can successfully play Twitch HEVC streams after installing HEVC Video Extensions, and Twitch reports the stream codec as:
hev1.1.6.L150.90.0.0.0.0.0
Firefox still reports:
MediaSource.isTypeSupported('video/mp4; codecs="hev1.1.6.L150.90"') false
and
navigator.mediaCapabilities.decodingInfo(...) supported: false
So it looks like Firefox specifically is not exposing HEVC support through MediaSource/MediaCapabilities, even though the HEVC codec appears to be installed and usable by Chromium-based browsers.
I also tested this link: https://test-videos.co.uk/bigbuckbunny/mp4-h265
The videos open on chrome but I get an error message in firefox.
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