Originally posted by poethius
As I understand it, the S715's convert everything to 1080p and then give you your choice of displaying the picture at 540p or 1080i. How does this work? Isn't there a negative impact on PQ through the multiple conversions? E.g., 1080i input gets deinterlaced, which can introduce artifacts, and then gets reinterlaced for display at 1080i. Isn't that worse than just displaying 1080i without any conversions? Even for 480i inputs, there may be some unnecessary introduction of deinterlacing artifacts.
Furthermore, how can the PQ be optimized simultaneously for 540p and 1080i? In both cases, 540 lines are written to the screen every 1/60 second, but, in 1080i, alternate fields are displaced by 1/2 a linewidth. Wouldn't you want a smaller spot size for 1080i, to render the higher vertical resolution, and a larger spot size for 540p, to reduce the space between the lines? Or is that not how it works?
And how does this compare with the Mits CRT RPTV's? They used to provide a similar choice, but between 480p and 1080i. (Apparently the new models no longer support 480p.)
I guess what I'm really asking is whether the choice is meaningful. If you have a progressive input (either 480p or 720p), will the picture look better at 540p? If you have an interlaced input (either 480i or 1080i), would the picture look better at 1080i? Or is the difference really subtle?
When 1080i (or 540p) is input into the Hitachi, it is displayed natively. No VirtualHD 1080p processing is applied. When any non-native rate is input, it is first converted to 1080p then back to 1080i for display. Any conversion causes artifacts, but the Hitachi does an admirable controlling the visibility of artifacts.
1080i is really just interleaved 540p fields (60 fields per sec), so there is not much difference in the processing VirtualHD must do to go to 1080i or 540p (60 frames per sec). In film mode, 3-2 pulldown detection recreates original progressive frames of the film. This is best displayed progressively (540p on the Hitachi). For 1080i display, 3-2 pulldown must be reapplied for interlacing.http://www.hometheaterhifi.com/volum...e-10-2000.html
I find that the DVD picture is more stable at 540p than 1080i (only noticeable on critical scenes...mini-blinds are great for testing!). Converting 720p to 1080i is noticeably better than 540p (as expected). However, I find that most STBs do a better job than the Hitachi converting to 1080i (I have done testing while viewing SNF on ESPNHD). XBox still looks great at 720p converted to 1080i on the Hitachi.
How does this compare to Mits? Well, the Mits [and Panny and Sony] sets that display 480p natively do a better job with DVD since there is no conversion taking place. It is easy for me to see the difference (I own both) but many people don't see a difference, the Hitachi scaler is pretty good (and using a scaling DVD player like the Zenith/LG or Denon can be even better).