Two hybrid error concealment schemes based on application of forward error control (FEC) coding in combination with passive error concealment techniques to different layers of coded data in a video transmission system are evaluated. It is shown that use of passive error concealment schemes alone generally does not provide sufficient protection against channel errors, especially in the case of video sequences with significant motion or scene changes. Motivated by these observations, a third hybrid scheme is introduced; this scheme involves adaptive application of FEC codes to high-priority information depending on the level of motion in a sequence. It is shown that through application of this adaptive motion-based scheme, significant savings in bandwidth may be obtained at the expense of only a negligible decrease in reconstructed image quality. Implementation of adaptive motion-based FEC coding in a multiresolution asynchronous transfer mode framework is discussed, and metrics for computing motion in both a subband and an MPEG-2 coding system are introduced.
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