1. A method for tracking content rendered on a content-rendering device that is communicably coupled to a content-server, said method comprising: sampling by said content-rendering device, a first audio component of said content at a sampling rate; generating and communicating to said content-server, a first audio fingerprint based on said sampled first audio component; suspending said sampling for a predetermined period of time based on detection of a scene change in said content; modifying said sampling rate after said predetermined period of time based on said detected scene change in said content, wherein said scene change is detected based on said communicated first audio fingerprint; generating and communicating to said content-server, a second audio fingerprint based on a second audio component of said content sampled at said modified sampling rate; receiving promotional content based on said second audio fingerprint generated at said modified sampling rate; and displaying said promotional content as an overlay on said content when said content is a commercial content comprising at least an advertisement, wherein said promotional content is determined based on said commercial content.