Firefox Community Forum

(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?

My Youtube video stutters every 6-10 seconds. When I turn off my HW acc off, this issue happened. Turning the HW acc on solve it, but the thing is if I have my HW acc on another problem came up, which is my Firefox will starts to blink. Anyone has a solution for this?

firefox has always been the brower i choose .

but lately firefox is unable to browes or play streams

i tryed all online steps to have it resolfed but still nothing

FF dev 155.0b5 (but this has been ongoing for 1+yr). W11p. Is there somewhere in settings where I can "disable" whatever is blocking videos from being seen? (for example BBC news videos). I have to go to troubleshoot mode to watch. I have previously disabled all potential blocking exts like ghostery & UBlock, but to no effect (still no videos). I have looked in security in settings. Otherwise, I either go to troubleshoot or open chrome. Or, is there an extension that will allow that video viewing? Please advise, thank you.

Hello All,

I have a somewhat confusing issue that I've only found two posts on Reddit mentioning previously, but there were no responses.

A short summary: On Discord's website, in an audio call, audio will progressively move from stereo/both ears to mono/only the right ear after anywhere from five to sixty seconds. This only occurs on Firefox, it does not occur on Chrome or Edge (with the same extensions, when applicable.) For the record - this also only occurs with the one headset. I've tried with a second headset and don't have the same issue, but I don't believe the Headset is solely to blame since the issue only happens on Firefox.

I have also tested on Firefox Nightly as a fresh install - no extensions, no settings changed, just install and login to Discord.

Specs:

ASUS TUF Dash F15 FX517ZR HP USB-C G5 Essential Dock (Monitors are connected through it) Windows 11 (August update/build 26200.9168) Razer Blackshark V2 Pro RZ04-0453 headset (Connects via USB-A Dongle plugged in to the laptop) Firefox (x64) (154.0.1)

Troubleshooting steps I've taken:

Removing the Audio driver for my computer and re-installing it. Removing/re-installing the drivers for the Headset. Verified all audio related drivers for my device are up to date. Verified the BIOS is up to date (it's solved unusual problems before) Toggling the "media.latency_preference" toggle in about:config (recommendation from a friend) Disabling all extensions on Discord. Disabling Firefox's strict mode on Discord. Verifying all audio related drivers for my device are up to date. Tested on a Firefox Nightly install (the first time it's been installed on my device). A separate browser (Chrome/Edge - the issue is not present) A separate headset (Issue is not present) Downloading Razer Synapse and disabling any "extra" features, and testing with various options on/off. Disabling any and all other Audio devices (speakers and microphones) while using the headset. Charging the Headset to full.

Things I haven't tested, but thought of:

Resetting Firefox in any capacity - I can, but hopefully testing with Nightly is sufficient. A different computer entirely - on my list, when I can next. A new User profile. Testing with no headset at all, and just utilizing the built-in speakers/microphone for the laptop.

Oddities:

Changing audio settings in Windows will "fix" the issue momentarily - for instance the "Spatial sound" option. Changing from one setting to "Off" (or vice versa) fixes the issue for the same ~5-60 seconds until it slowly goes back to the right ear. These options are present for every device, even ones not experiencing this issue.

It's very odd to me because on one hand it may be the headset, but then the issue is only present in Firefox.

Any help or things to test would be greatly appreciated!

Thank you.

Since I updated to Firefox v154 (on Windows 11 w/latest updates) Substack videos freeze at random times 15-30 minutes into playback (never right away). If I close the tab and reuse the original link, playback resumes more at less where it froze, but this is very annoying and happens almost every video. Other online videos (e.g. YouTube) don't seem to have this problem -- but I rarely watch hour-long videos outside of Substack, so I can't confirm that the problem doesn't exist elsewhere. This only seems to occur after streaming 15+ minutes so probably a subtle bug.

Any time I have another application open and I pause a YouTube video or music everything on my computer mutes. I tried to disable hardware media keys in config but that just mutes my entire browser

Firefox tabs intermittently missing mute button when opening tab with audio/video. Doesn't matter if its on autoplay allowing audio or if audio is blocked.

Example: When opening kick, twitch, YouTube or any other tab with audio.

Sometimes the mute button will be available, and sometimes its not. If you duplicate the tab without audio sometimes the new duplicated tab will have the mute button.

The first time i noticed this issue is after the most recent update (154.0).

You can right click the tab missing the mute button and mute. The mute button then appears, until you click it to un-mute the tab. It then disappears and the only way to mute again is to right click/mute or type mute in the address bar.

Playback works correctly usually, but if I jump forward or backwards in time it sometimes never loads. This also completely bricks the whole brower, all other tabs etc, until I close firefox and restart it. This happens on all vods of twitch, and also livestreams where I am able to rewind (subscriber function). I have no extensions enabled, and have the default settings on firefox etc. ("Use recommended performance settings") Video of it happening: https://www.youtube.com/watch?v=3difRLhE-cA

usually when i click my keyboard's knob thing, it will pause and unpause whatever media is playing. but recently it's stopped doing that. it will work for anywhere between 2 mintues to 30 minutes, but eventually it stops. the only way to make it work again is to refresh the page or start a new page. the troubleshooting steps i've taken is: -close other media software (spotify, other tabs etc) -gone to abouy:config and typed in mediakey to check it works. also turned it off and on for good measure -turned off xbox gamebar -turned my pc off and on again. none of those worked i also thought it might be autoplay being turned off, but it didnt do anything. please help. thank you

so i found a strange problem that when i connect headphones to my computer i have a very quiet sound on firefox videos (youtube an ect.). it is not a low volume on my computer or headphones settings, in other browsers everything works smoothly, i dont know why is is only a problem here in firefox

After a Windows 11 update my Firefox browser no longer has any audio. The sound is turned all the way up in the Sound Mixer and I have no Bluetooth devices connected. After it initially happened I connected my Bluetooth earbuds and it worked for a few minutes before it too lost audio.

I have audio on all my other applications.

I'm running the latest version of Firefox on the latest version of Windows 11, and I'm trying to watch TV shows on PBS's Passport service. I get the video but not the sound. It's been like this since Saturday. I don't have this problem at all with Chrome or Edge. Is anyone else having this problem? JT