The DCR-SR21 has a Digital image stabiliser which is better than the Optical image stabiliser found on most video cameras of this age and type. Some compact cameras have digital Image stabilisation only, which simply boosts camera sensitivity (ISO) to obtain a faster shutter speeds to help prevent blur. No hardware is involved.
A Digital image stabiliser is actually the worst image stabiliser type across all video cameras of a comparable type and age to the DCR-SR21.
Across comparable types of video camera the best image stabiliser type is Optical.