Lately, significant efforts have being put into proposing various solutions for increasing multimedia viewers' perceived quality levels. One innovative avenue is to enhance users' quality of experience (QoE) by extending the classic audio-visual multimedia content to stimulate also other human senses such as olfaction, tactile, etc. In this context, this paper focuses on olfaction-enhanced multimedia content and presents the results of an experimental study which looked at user perception of inter-stream synchronization between olfactory data and video, whereby the audio used provides no contextual information. The study investigates how age and gender influence users' perception of the temporal boundaries within which they perceive olfactory data and video to be synchronized. The impact on user QoE levels (considering sense of enjoyment, relevance and reality) during synchronous and asynchronous presentations of olfactory and video media is also analyzed and discussed. The results show that there are significant differences in terms of how users of various gender and age groups perceive the skew between olfaction and video content and in their QoE levels.