A method of playing audio data by a portable device is disclosed. The method starts with an optical sensor of the portable device sensing a tag on a surface. The tag encodes an identity of the surface and a location of the tag on the surface. Audio data is recorded by an audio system of the portable...http://www.google.com.au/patents/US7979149?utm_source=gb-gplus-sharePatent US7979149 - Audio data associated with a surface and a position on the surface
