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To support spatial scalability, the scalable extension of H.264/AVC (SVC) uses video cropping or uniform scaling to downscale the original higher-resolution (HR) sequence to a lower resolution (LR) one. Both operations, however, will cause critical visual information loss in the retargeted frames. The content-adaptive spatial scalability SVC coders (CASS-SVC) use non-homogeneous scaling to avoid critical information loss, which, however, requires to send additional side information to signal the decoder, thereby degrading coding efficiency significantly. To address the problem, we propose a low-overhead CASS-SVC coder consisting of three main modules: a mosaic-guided video retargeter, a side-information coder, and a non-homogeneous inter-layer predictive coder. Our experimental results demonstrate that, compared to existing CASS-SVC coders, our method cannot only well preserve subjective quality of important content in the LR sequence, but also significantly improves the coding efficiency of HR sequence. Index Terms—Video adaptation, video retargeting, spatial scalability, scalable video coding. 1