HW decoders will not send the deblocking barrier to external memory (typically). Instead you will buffer the required rows until you have decoded the next line of macroblocks. As long as the filter margin are the same this will work fine in itself but you will not have done the buffering at the same place you did deblocking or any of the simpler overlap filters. In that way you will force larger changes to your architecture. Similarly your transform unit is likely not set up to handle this so it requires redesign. Getting to many of these hurdles in can be the death of adoption for the CODEC.