The missing step before MP4

Even after full-screen stills joined the gameplay recorder, a recording run still stopped before producing its MP4: ffmpeg: command not found. The browser had recorded the session, but the tool could not complete the conversion that turns it into the file the workflow expects.

Restore the missing prerequisite#

The image had lost a package the recorder already depended on. ffmpeg had been installed earlier, then disappeared when the image’s package-install block was rewritten for shared development tooling. The Dockerfile and the recorder’s instructions still assumed it was there, so every conversion failed at the same point.

The fix restores the package in the base image stage, where all image targets inherit it. That keeps the recording tool’s requirement with the environment that runs it instead of relying on a manual repair after the container starts.

Before: ffmpeg: command not found
After:  H.264 video, 412×914, 70.9 seconds

The conversion succeeded after installing the package in the running container, but the changed image had not yet been rebuilt. The Dockerfile now carries the missing dependency; rebuilding the image is the check that remains for the next container.