Blu ray is usually between 20-40gb, so if you want burn it on a dvd disc (4-9gb) and keep the HD quality, you should split it into several dvd discs. Here is a tutorial to convert and split Blu-ray to AVCHD DVD.
Step 1, Decrypt and copy Blu-ray to hard drive using Blu-ray Decrypter.
Step 2, Trim unneeded streams (audio or subtitle) using TsRemux.
Step 3, Split the new .m2ts file into several .m2ts file using HDBDSplitGUI.
Step 4, Convert .m2ts to Blu-ray disc structure folder using TsRemux.
Step 5, Burn the Blu-ray disc structure folder to a blank DVD Disc.