Reliable transmission of video over heterogeneous networks requires efficient coding, as well as scalability to different client capabilities, system resources and network conditions. Scalable video coding can provide a full scalability comprising temporal scalability, spatial scalability and quality scalability to increase its adaptability to network and client conditions. It encodes the original video at a full resolution, but enables extracting partial streams to reconstruct the video depending on the specific rate and resolution required by a certain application. This paper addresses the problem of scalable bitstream extraction. Given the bandwidth constraint and the display resolution of the end user, the proposed algorithm will decide the spatial resolution of the sub-stream to be extracted based on the analysis of the content information to maximize the perceptual video quality. Experimental results demonstrate the efficiency of the proposed algorithm.