Which feature is NOT a requirement for accessible media players?

The correct choice identifies a feature that is not a requirement for accessible media players. Automatic content update refers to the capability of updating content dynamically when a media player is in use, but it is not a fundamental aspect required for accessibility. Accessibility primarily focuses on ensuring that users, including those with disabilities, can effectively interact with the media player and the content it delivers.

The other features are essential for accessibility. Clear labeling and sufficient contrast ensure that all users can easily identify and use the controls of the media player. User interface operability without a mouse caters to users who rely on keyboard navigation or assistive technologies, enabling them to interact with the media without mouse input. A visible keyboard focus indicator is crucial for users navigating through controls using a keyboard, as it allows them to see where their focus is at any given moment, enhancing usability.

Thus, while automatic content updates may enhance the functionality or user experience of a media player, it does not fall under the fundamental requirements for ensuring accessibility.