Video Asylum

Posted by oscar (A) on June 08, 2007 at 18:13:03

In Reply to: RE: Big Difference? posted by Robertc88 on June 08, 2007 at 10:27:23

What can happen is a studio will constrain a movie release to work within the constraints of a Blu-Ray single layer (25G) disc instead of allowing for the storage capacity of a dual layer (30G) HD-DVD disc. This might be done for economic reasons (only one set of video compression required). This forces the video bitrate to be slightly lower than needed for the HD-DVD release. Or a movie release will be designed to work within the constraints of HD-DVD (30G) instead allowing for the 50G DL Blu-ray disc capacity. Again, this forces the video bitrate to be significantly lower than than allowed by the larger capacity format.

It's a matter of debate how significant the differences are between low and high bitrate VC-1 and AVC encodes. There are those who will claim the Blu-Ray "Flags of Our Father" and "PRestige" relatively high bitrate AVC encodes are superior in PQ to the HD-DVD encodes using a lower bit rate VC1 encode. Another example I've read about is the Blu-Ray AVC encode for "Coming to America" is inferior to the HD-DVD VC1 encode of the same movie. The Blu-Ray is a single layer with 5G less space to play with so the encode has to be at a lower bitrate. Coincidence ? Maybe not a large sampling from which to draw (Premature?) conclusions, but time will tell with future releases of higher bitrate encodes on 50G discs.

Also, for whatever reason (storage/bandwidth constraints perhaps?), there are more Blu-Ray discs with uncompressed PCM tracks than for HD-DVD. On every disc I've ever done comparisons with, the uncompressed PCM is considerably better than their lossy DD counterparts. The 50G Blu-Ray discs give you a lot of flexibility video and audio bitrates that can't be duplicated with 30G HD-DVD discs.