Method and apparatus for aligning signals

A method of aligning a first signal comprising a sequence of frames with a second signal comprising a sequence of frames, the method comprising the steps of:

• determining a similarity measure between each of a plurality of frames of the first signal and each of a plurality of frames of the second signal;
• assigning a matching value to each frame of said plurality of frames of the first signal wherein the matching value indicates a relative position of a matching frame in the second signal, by repeating the sub-steps of:
• selecting a subset of frames of the first signal and generating a relative delay histogram, the histogram comprising a set of values corresponding to each of a set of relative delays by:
• for each frame of said subset identifying the frame of the second signal having the greatest similarity with said frame;
• determining the relative delay between the identified frame of the second signal and said frame of the first signal;
• and
• incrementing the value of the histogram corresponding to said relative delay;
• identifying one or more peaks in the relative delay histogram;
• assigning a matching value to each frame contributing to a peak in dependence upon said identified peaks;
• determining a frame which has no matching value assigned;
• and
• assigning a matching value in dependence upon a matching value assigned to a preceding frame and a matching value assigned to a subsequent frame.