Time-based media: video only

This page deals with the other half of criterion 1.2.1 and is all about video content. The criterion states:

Prerecorded video-only: Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.

So what is prerecorded video-only content? Well the immediate things that spring to mind are:

... but there are probably loads more.



For video-only content, an alternative to the video might be a transcript. Transcripts have a clear advantage over audio description. They can be read by a person who is deafblind because it is screen reader friendly and can be read on a Braille output device.

A transcript should be an accurate text description of what is happening in the video. It should be easy to find and open. And it should go without saying that it must be in an accessible format, so that it can be read by a screen reader.

I've taken some dashcam footage of a journey under the Tyne Tunnel. It shows the road layout and what to expect. It might be useful to somebody who is nervous about tunnels and wants to be prepared for the experience.

Video of journey under the Tyne Tunnel


Transcript for video

We are joining the main road from a slip road. We pass the vehicle inspection lane on our left. The traffic on the main A19 is moving very slowly. Blue traffic signs tell us to switch on our radio and dipped headlights. We queue to join the main traffic. Cars in front of us begin to indicate right to join the A19. The traffic is moving so slowly that we can filter in turn.

Inside the tunnel, there are two lanes, separated by a double white line. The tunnel has lights down the centre and right side of the roof. The right hand lane is moving faster than the left. The cars in front of us keep stopping, with their red brake lights shining in the dull light.

The road goes downhill as we descend under the River Tyne. Every so often, there is a door on the left. The road begins to curve slightly to the right as it goes down. When we get to the bottom of the hill, the road levels out and becomes straight. The traffic is not so busy now and is moving at about 30 mph, with plenty of gaps between vehicles.

The road starts to go uphill as we head towards the other side of the river. A little before the end of the tunnel, the road begins to turn quite sharply to the left. This left curve continues for a full 360 degrees.

As we emerge from the tunnel, the light is bright, but then rain starts to hit the windscreen. The road continues to curve sharply to the left. There is an exit slipway to our left, closely followed by a joining slipway. The road straightens out and the A19 continues as a normal dual carriageway.

I've put my transcript in its own box, which is a set height and scrolls vertically. This makes it easier for those who don't want to read it to move past. You could use a Word document though, and provide a link to it. I just prefer it to be on the page, so that it is less keystrokes for a blind person to access it.

Audio description

Audio description is a description of what is happening visually in the video. It enables a blind person to understand what is happening. For many blind people, a well-created audio description can offer a better experience than a transcript. However, it is important to remember that an audio description cannot be accessed via a screen reader and is therefore not helpful to someone who is deafblind.

It is not usually possible to have an audio description that can be toggled on and off in the same way that captions can be. I look forward to a day when that is a standard feature but for now, we need to create a separate version of the video, which includes audio description.

For the video above, I have produced an audio described version. I used Adobe Audition to record the audio clips, by reading from the transcript, one paragraph at a time. I then dropped them into Premiere Pro so that I could move them to the correct place in the video.

Video of journey under the Tyne Tunnel with audio description


There are some brief sections of the video, where the audio doesn't perfectly line up with the visual content, but this is not a major problem. The aim is to ensure that a blind person can understand the content as well as a sighted person.