Nowadays, a large variety of emerging applications (clickable, video, interactive high definition television, intelligent interfaces) do not only process the multimedia content (audio, video, 3D,...) but some additional data directly connected to it, as well. This enrichment information is usuall transmitted and stored as an additional independent stream (metadata). Such an approach can be restrictive sometimes, mainly for the networks/application with strict bandwidth and/or protocol constraints. An alternative solution is advanced and discussed in this paper. The principle consists in transmitting the metadata via in-band channels obtained by means of data hiding (watermarking) techniques. The challenge is to design data hiding techniques reaching the trade off among transparency (the enrichment process should not alter the perceptual quality of the host media), robustness (possibility to recover the metadata at the end user even when the high distortions occur through the channel) and data payload (the amount of metadata which can be inserted). The paper investigates the feasibility of such techniques by evaluating the maximal data payload (the watermarking capacity) under given robustness and transparency constraints. The results are compared to the resources needed by some existing enrichment applications. The experiments are carried out in collaboration with the French mobile service operator SFR (Vodafone Group) and consider video sequences watermarked in the DWT domain.