If recording direct to the DVD it will be slow. If you are copying from the hard drive to a DVD I think it was called dubbing will depend on the disks you are using and the file size and type you are trying to copy. If the file is too big for the disk it will have to be adjusted and can take longer than the original film/program.
As I can only find reviews from 2006 for the Sony RDR HX510 it's possible due to it's age the lens in the DVD drive is on it's way out.
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