Please check the OVDecodeRender Sample's documentation. It mentions a wikipedia link at the end, giving details of the supported hardware.
Please note there may be some changes you may have to do to the sample if you are working wirh SDK 2.8 because the OVDecode Sample has not been properly updated after SDK 2.7 release. This is a known issue, and will be fixed soon.
Mostly the issue being the renaming of OVDecode.dll to OpenVideo.dll.
About OpenEncode, supported Platforms are:
• Tahiti XT GPU
• Cape Verde GPU
So AFAIK, it is not supported on your HD 6xxx cards.