Digital time delay and integration (DTDI) mosaic video sequences captured by high-speed DTDI line-scan cameras are commonly used in industrial print inspection and high-speed capture applications. To reduce the memory requirement for saving these video sequences, it is necessary to compress them. In this paper, we present an efficient chroma subsampling strategy for compressing DTDI mosaic video sequences in H.264/AVC. Based on the color domain transform between the RGB domain and the YUV domain, a position-selection strategy is proposed to determine the two subsampling chroma components, U and V, according to the DTDI mosaic structure. The quality of reconstructed DTDI video sequences is better than those reconstructed by conventional methods. By experimenting on some popular test DTDI mosaic video sequences, the results turned out to be superior than conventional ones that adopt H.264/AVC as compression standard.