Subjective quality assessment is widely used to understand and to study human perception of multimedia quality and as a basis for developing objective metrics to automatically predict the quality of audiovisual presentations. There are several recognized international protocols and procedures for reliable assessment of quality in multimedia systems and services, with emphasis on speech, audio and video modalities. However, the aspect of certification is not yet well understood in this context. This paper discusses various issues regarding certification of multimedia quality assessment. To be concrete, the discussion is illustrated by the procedure implemented to assess 3D video compression technologies within the MPEG effort for the definition of a 3D video coding standard. Selected results from four laboratories, Acreo, EPFL, NTNU and UBC, which participated in the assessment are presented. This case study is used in an early attempt to define a process for certification of subjective test campaigns, based on a cross-validation of the test results across different laboratories, towards the ultimate goal of Quality of Experience (QoE) certification.