Image　watermarking　is　a　popular　research　topic　in　signal　processing.　The　paper　presents　a　blind　watermarking　scheme　for　3D　videos.　Given　a　3D　video,　each　frame　of　both　views　is　divided　into　blocks.　Watermark　information　is　embedded　by　modulating　selected　DCT　coefficients　of　each　block.　The　modulation　strength　is　controlled　by　multi-modal　visual　redundancies　existing　in　the　3D　video.　Specifically,　we　compute　an　intra-frame　Just-noticeable　Distortion　(JND)　value　and　an　inter-frame　reference　value　for　the　block　to　determine　the　strength.　The　former　reflects　the　visual　redundancies　in　the　image　plane.　The　latter　represents　the　visual　redundancies　of　the　block　from　aspects　of　motion　between　sequential　frames　and　disparity　between　the　left　and　right　views.　We　validate　the　robustness　of　the　proposed　watermarking　scheme　under　various　attacks　through　experiments.　More　importantly,　the　visual　quality　of　the　3D　videos　watermarked　by　our　scheme　is　proved　to　be　as　good　as　that　of　the　original　videos,　by　a　proposed　LDQ　(Loss　of　Disparity　Quality)　criterion　specially　designed　for　3D　videos,　as　well　as　PSNR　of　single　views.　©　Springer　International　Publishing　AG　2017.