What Does Visual Impaired Mean?

Visual Impaired is a yes-or-no marker attached to one track inside a media file. It says that the track is there for people who cannot see the picture, which in practice almost always means an extra audio track that describes out loud what is happening on screen.

Which files carry it, and who sets it

This marker lives on the individual tracks of video files. MKV and WebM have a dedicated track flag for it. MP4, MOV and broadcast MPEG-TS streams carry the same idea, and inspection tools list the flag for every track in a file, whether it is switched on or not. It normally sits on an audio track, and sometimes on a subtitle track.

The value comes from whoever assembled the file: a broadcaster, a streaming service, a disc author, or anyone muxing tracks together with software such as mkvmerge or ffmpeg, both of which can set the flag deliberately. A camera never writes it, and a phone never writes it, because the flag describes an editorial decision rather than something that was measured.

Accessibility information for other kinds of file works differently and appears elsewhere in a report. An image carries a written description in its metadata fields, and a tagged PDF carries alternative text for its pictures, both of which a screen reader can read aloud. Those serve the same purpose as a described soundtrack, but they are separate fields, not this flag.

What the value looks like

The value is a switch with two states, shown as 0 for off and 1 for on. Some tools print No and Yes instead. Most tracks in most files show 0, simply because most files have no described soundtrack.

A film that does have one usually shows two or more audio tracks: the ordinary soundtrack with the flag off, and a second track with the flag set to 1, often also given a language and a title such as Audio Description. There is no unit and no scale, and no in-between value.

Why it matters

This is a playback and accessibility field, and it earns its keep by making the right track easy to find. Players, smart TVs and set-top boxes read the flag to offer a description option and to select that track automatically for a viewer who has asked for one. Nothing about the audio itself identifies a described track, so without the flag the software has nothing to go on.

That is what makes the two failure modes worth checking. If a file contains a described soundtrack and the flag is not set, the track looks like nothing more than a second language, and the viewers who need it are left hunting through a menu. If the flag is set on the wrong track by mistake, a player can start the film with narration that nobody asked for. When a file is handed over to a broadcaster or a platform, these track flags are part of what makes a described soundtrack usable at the other end.

There is no privacy question here. The flag says nothing about you, your device or where the file was made. It describes the purpose of a track, and nothing else.