This paper proposes a content authentication scheme for MPEG-4 FGS (fine-granular scalability) video based on digital fragile watermarking using Bitplane-Coding Watermarking (BCW). In embedding procedure, the watermark information is embedded into every 8×8 block of residual bit-planes in the enhancement layer while encoding to MPEG-4 FGS video stream. The watermark bit is modulated by modifying a specified bit in each 8×8 bitplane such that the even/odd value of the total number of "1" bits can meet the corresponding watermark information. In extracting procedure, the embedded signal can be detected from each block of residual bit-planes by judging the total number of "1" bits in the block is even or odd. The detected signal is used to localize errors and claim ownership of the video content by decoding it to copyrights information. It is worth mention that we use runlength coding steps to select the optimal position for embedding watermark information in order to increase the coding efficiency. Experimental results are presented validating the effectiveness of the proposed approach. It is found that our proposed method needs no complicated computation. Furthermore, we found that the compression ratio is increasing due to the selection of optimal position for imposing the watermark.