>>615 DXVAだと縦が576ラインを境にしてSDとHDを切り分けるみたいです。
NTSCだと縦480だけど、PALが縦576だからでしょうね。
http://msdn.microsoft.com/en-us/library/ms698715(VS.85).aspx
For standard-definition content, treat as DXVA2_VideoTransferMatrix_BT601.
For high-definition content, treat as DXVA2_VideoTransferMatrix_BT709.
(High-definition content is defined for this purpose as anything with a source height greater than 576 lines.)