A device, computer program product and a method, the method may include: Extracting first size information about sizes of different frames of a first segment of an encrypted first streaming media flow that has a first CBR. Extracting second size information about sizes of different frames of a second segment of a second streaming media flow that has a second CBR that equals the second CBR. The extracting of the first and second size information and the determining of the relationship are executed without decrypting the first and second encrypted streaming media flows. Determining, based on first and second size information and on the first and second type information, a relationship between qualities of the first and second streaming media flows based on the first and second size information. Extracting first type information indicative of which frame of the first segment is the first reference frame and which frames of the first segment are the first non-reference frames. Extracting second type information indicative of which frame of the second segment is the second reference frame and which frames of the second segment are the second non-reference frames.