Ad-mix Solutions

Audio (Video) Description/Commentary auto Insertion (AD insertion)

In Europe we have Audio Description. In USA it is Video Description. The function, though, is the same, which is to supply a commentary track which is of particular use to the visually impaired. When media is supplied to televisions and set top boxes, the commentary can often be streamed in parallel to the main sound track and selected in the home. When broadcasting to devices such as tablets and computers, this is usually not possible. For these cases it is therefore necessary to premix the commentary over the main audio, and let the end user select either the normal audio, or the audio with commentary. The AD mix for Engine provides a range of solutions for premixing the commentary using a standard Pan/Fade control track.

The process uses a mono control track compatible with the BBC WHP198 “Audio Description Studio Signal”, together with a mono commentary track. The control is used to fade the main soundtrack (usually stereo) at appropriate places, with the commentary then being added over the top, taking in to account any pan values specified in the control track. The control track and the commentary track are usually carried together in a stereo pair, but this is not essential.

Engine‘s AD module is designed for maximum flexibility, with a number of different configurations supported. As an example, the main soundtrack and the commentary and control data can be contained within a single media file…

The image below shows the Engine workflow diagram that represents this workflow.

Often the main soundtrack is in a media file and the commentary and control are in a stereo WAV, as in the following block diagram.

This can be handled easily in Engine, and illustrated in the following workflow diagram produced by Engine. The MXF input has red routing lines and the WAV input has blue routing lines, and are mixed together in the Audio Descriptor block.