I have a mac 2.66, 10.6.4 running a recently purchased Decklink SDI card with CS5 Adobe Suite. After importing a targa image sequence into both an HD 1920x1080 and SD 720x576 sequence, I want to record to Digibeta. I see in the controls preferences that I can downconvert from HD to SD. I presume means that there is no render needed as the card does the conversion (that is what the manual says). For the moment, however I configure the sequence or the Bm prefs, the edit to tape renders the file. Also, once the sequence is rendered, the edit tape goes to an 'unknown error'. Mind you, when export the file as an uncompressed 422, all is well.
So in short, how does the HD SD conversion ork in Premiere?