Re: Blu-ray Dolby Digital vs HS. DDplus...
Here is what these formats are capable of...
Dolby Digital on a DVD is capable up to 448kbps.
Dolby Digital on an HD DVD is capable up to 504kbps
Dolby Digital on an Blu-ray is capable up to 640kbps
Dolby Digital Plus on an HD DVD is currently limited to a max of 3.0Mbps
Dolby Digital Plus on a Blu-ray is currently limited to a max of 1.7Mbps
Dolby TrueHD on HD DVD and Blu-ray are both represented at 18Mbps
So yes that 640kbps Dolby Digital track may be present on a Blu-ray. However, it is less than half of what a typical Dolby Digital Plus track offers (typically a minimum of 1.5Mbps).
Hope that clarifies things.