Sorry for the misunderstanding. Probably I did not get what you mean by "so when media file is playing the audio description should be added". Could you please walk me through a sample scenario you want to achieve?
I have few questions. When the user plays the media file, where do you want to add the audio description? Do you want the audio description to play while the media file is playing as well? Or do you want the user, before playing the media file to hear the audio description and as soon as the audio description finishes, then to start the media file again.
It would be great if you can give me more information on your scenario so I can assist you better.
the Telerik team