No video with supported format and MIME type found

[Swarkin]

Captchas

• [x] I have read the instructions.
• [x] I have searched existing issues and avoided creating duplicates.
• [x] I am not filing an enhancement request.
• [x] I have checked that this issue cannot be reproduced on Mozilla Firefox.
• [x] I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

Im unable to play videos on Github on any of my devices when using specifically Zen browser.

Version

1.12.8b

What platform are you seeing the problem on?

Windows - x64

What component is this issue related to?

Media Controler

Relevant log output if applicable

[0Ky]

Have you modified about:config (advanced preference settings) or using a custom user.js file? If you have media.mp4.enabled set to false it would also cause the same issue. I'm running the same version on Windows and not having any issues.

[Swarkin]

I havent modified anything inside about:config directly except for browser.tabs.closeWindowWithLastTab: true which shouldnt be relevant and I do not have an user.js file. I can watch Youtube just fine and all mp4's on streamable's homepage also play automatically. For now I have only noticed issues with videos embedded in Github?

Example:

https://github.com/user-attachments/assets/12dd7375-5f0c-44f4-80a6-cbd740ff717f

prefs.js

[Swarkin]

Snippet of the browser console:

Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded. [8560](https://github.com/zen-browser/desktop/issues/8560#issuecomment-2905786332)
Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded, error: Error Code: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006) [8560](https://github.com/zen-browser/desktop/issues/8560#issuecomment-2905786332)
Referrer Policy: Ignoring the less restricted referrer policy “no-referrer-when-downgrade” for the cross-site request: https://private-user-images.githubusercontent.com/102416174/447157429-04c502b2-6a0b-4831-a549-2be7208067fc.png?jwt=[redacted] [447157429-04c502b2-6a0b-4831-a549-2be7208067fc.png](https://private-user-images.githubusercontent.com/102416174/447157429-04c502b2-6a0b-4831-a549-2be7208067fc.png?jwt=[redacted])
Referrer Policy: Ignoring the less restricted referrer policy “no-referrer-when-downgrade” for the cross-site request: https://private-user-images.githubusercontent.com/102416174/447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png?jwt=[redacted] [447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png](https://private-user-images.githubusercontent.com/102416174/447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png?jwt=[redacted])
Referrer Policy: Ignoring the less restricted referrer policy “no-referrer-when-downgrade” for the cross-site request: https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] [447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4](https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted])
Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded. [8560](https://github.com/zen-browser/desktop/issues/8560#issuecomment-2905786332)
Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded, error: Error Code: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006) [8560](https://github.com/zen-browser/desktop/issues/8560#issuecomment-2905786332)
Referrer Policy: Ignoring the less restricted referrer policy “no-referrer-when-downgrade” for the cross-site request: https://private-user-images.githubusercontent.com/102416174/447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png?jwt=[redacted] [447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png](https://private-user-images.githubusercontent.com/102416174/447231099-afca47e9-3697-4190-a7ba-6615c9c23312.png?jwt=[redacted])
Referrer Policy: Ignoring the less restricted referrer policy “no-referrer-when-downgrade” for the cross-site request: https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] [447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4](https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted])
Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded. [8560](https://github.com/zen-browser/desktop/issues/8560#issuecomment-2905786332)
Media resource https://private-user-images.githubusercontent.com/102416174/447230677-12dd7375-5f0c-44f4-80a6-cbd740ff717f.mp4?jwt=[redacted] could not be decoded, error: Error Code: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006)

[0Ky]

I havent modified anything inside about:config directly

Interesting, I've noticed some preferences were changed, which are different from default settings, but I have a feeling it's not actually related. Are you able to playback this video that was uploaded almost 2 months ago on GitHub. If you are able to, then I'm starting to think it might be an issue with GitHub... Because, I've unintentionally replicated the issue, the video you shared doesn't play for me either, even on other browsers that I haven't used or updated for a long time, including Chrome based ones. _{* These tests were conducted within a VM}

Here's a screenshot, showing the video (left side) you've shared is unplayable, but the one I have uploaded previously (right side) is playable:

It would seem the video is served corrupted?

Downloading the video via curl seems to work without any issues, maybe GitHub is somehow corrupting the video, it also seems to play that video only when hardware acceleration is enabled and not at all within a VM.

The video you shared is using the following codec:

codec_name=hevc
codec_long_name=H.265 / HEVC (High Efficiency Video Coding)
codec_type=video
codec_tag_string=hev1
codec_tag=0x31766568

When you go to about:support#media, do you see HEVC supported for Hardware Decoding ? Also, can you share the video as a zip, to ensure no re-compression occurs for video files via filebin or something. I'm going to verify the integrity of the file and compare it against the the one provided by GitHub.

[0Ky]

https://github.com/user-attachments/assets/d958aa08-3788-4265-bbd5-02898d5f41b7

Looks like GitHub doesn't perform video file integrity checks during upload, it could be that the video file is corrupted before the user even uploads the file...

[Swarkin]

I can play back the video from the linked issue perfectly fine.

This is what about:support#media shows in the Codec section:

I have a RX 6700 XT dedicated GPU and (for now) an intel i5-9600k. Windows 11 LTSC 26100.1742

Im able to play the video locally using VLC with no issues. It was recorded using OBS using the AMD HW H.264 (AVC) video encoder.

VLC seems to be using hardware decoding as suggested by the GPU usage:

I zipped the original video file (after one round-trip to the recycle bin and back, but that should not have modified the file in any way) here: 2025-05-24_10-15-23.zip

[0Ky]

@Swarkin Ah, it turns out HEVC/H.265 isn't supported in browsers without hardware acceleration, so you either don't have it enabled, where layers.acceleration.disabled should be false or that your hardware is unable to decode the video.

[Swarkin]

That is very weird, it can hardware-encode this format but not hardware-decode? Also, VLC seems to be using almost no CPU which suggests it is indeed using hardware decoding, but im unsure.

[0Ky]

The screenshot you shared is also evident that something is up with your hardware/OS/driver, it should look something like this:

Note that in your image, HEVC is unsupported for Hardware Decoding.

[0Ky]

@Swarkin By the looks of it, this isn't an issue with Zen browser. I think in Windows LTSC (Long-Term Servicing Channel) , HEVC codec might not be included, due to licensing. Can you confirm by running Get-AppxPackage -Name *HEVC* in powershell? Also, VLC could be using DXVA, which explains why you see GPU usage.

[Swarkin]

I see, that was the issue!

After installing the AV1 and HEVC extensions, i got these two corresponding codecs to work:

I dont know whether there are more of these extensions, but video playback works now.

They can be found on the microsoft store, or downloaded using https://store.rg-adguard.net for people that do not want to use it. I also zipped the appinstaller files directly here: codecs.zip