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AsciiDoc output does not render video:: tags as expected

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Summary

In a repo, I have my documentation as Asciidoc files, but I am having difficulties using the video tag as per https://docs.gitlab.com/ee/user/asciidoc.html#multimedia

Steps to reproduce:

  1. Use video:: in a README.adoc file, extract follows
[…]
== Abridged Video of a FDI based install

.FDI demo, with boring wait times cut out
video::videos/FDI-for-WS8-demo-homelab.mp4[width=480,opts=muted]

== Plan B
[…]

  1. of course have a valid video file in the directory videos. FWIW because videos are large, the file was added with Git Large File Storage (LFS)

  2. commit and push to my GitLab (CE, always latest, today it's gitlab-ce-17.0.1-ce.0.el8.x86_64)

  3. Access the GitLab webUI rendering of the repo with a modern browser that can handle H.264. In my case that's Firefox (always latest in Fedora current, today firefox-126.0-7.fc40.x86_64)

Expected result

GitLab webUI rendering of the adoc file should show an embedded video player if the browser can handle it and if the browser cannot, then it should show something along the lines of Your browser does not support the video tag, Here is a link to the video instead. (As shown for example at https://developer.mozilla.org/en-US/docs/Web/HTML/Element/video#usage_notes )

Actual result

In GitLab webUI, I always get Your browser does not support the video tag. shown when viewing the README.adoc no matter which browser I use. I know for a fact that the Firefox I use does handle HTML 5 video just fine (see further below how a commandline conversion leads to a html file the browser handles just fine).

Additional info

A) If I use rubygem-asciidoctor-2.0.20-6.fc40.noarch, asciidoctor --backend=html5 README.adoc, and then open the resulting README.html I get the behaviour I expect; if the browser can handle the video (H.264 in MP4 container) I get an in-line player shown where I can press play, enter fullscreen, seek, etc.

The README.html I manually generated opens fine and shows an embedded video player in these (firefox is my primary browser)

  • Firefox 126.0 (n.b. I enabled the "OpenH264 Video Codec provided by Cisco Systems, Inc." plugin in FF ages ago, be sure to enable it when trying to reproduce this bug and using a H.264 video)
  • Chromium 125.0.6422.141 (I actually did not expect that one to have H.264 support)
  • Chrome 125.0.6422.141

And in dillo-3.1.0-2.fc40.x86_64 I get the expected [VIDEO]Your browser does not support the video tag. with the text being a link to the mp4 file.

I am hoping that my understanding that GitLab uses the same rubygem is correct and thus that there is a way to get this to work with the GitLab webUI rendering the adoc for easy viewing.

B) I've seen #333714 (closed) this is not quite the same, I only have trouble with Asciidoc documents.

In a README.md, using

![video showing a Foreman Discovery Image install of WS8 in my homelab](videos/FDI for WS8 demo homelab.mp4){width=25%}

gives me the expected result.

C) While using GLFM instead of adoc might seem like an easy workaround, it is not an option in this case. I need the documentation in the repo to remain in the Ascioidoc format, it being shown in the GitLab webUI is just one of the uses these adoc files get, there are other uses (outside the GitLab webUI) for them too.

Edited by 🤖 GitLab Bot 🤖