DVI changes output resolution?

[TrantaLocked]

I discovered something unexpected but ultimately beneficial when messing with my OSSC settings with a PS2 source. When I change the OSSC (firmware v0.86) TX mode under Output opt. to DVI, the picture clarity improves, and my LG C1 reports the horizontal resolution doubling but not the vertical (from 640x480i in TX HDMI mode to 1280x480i in TX DVI mode). The DVI image shows up in widescreen with the LG C1 set to “original” aspect ratio, but it can be squeezed back with “4:3” aspect ratio mode, under which the image proportions are the exact same as TX HDMI mode on the OSSC. It is important to note that the exact numbers showing on my C1’s resolution report box (press the green button seven times to show) are not exactly 640x480i as I’ve changed some of the sample and frame settings on the OSSC in order to get the image at the correct pixel proportions and to fit the screen without a border.

At first I thought the clarity difference was due to a difference in how the TV does upscaling depending on the content type, but the TV is reporting an entirely different resolution. It seems like the image is being doubled horizontally but not vertically, but for me this is a huge plus as the normal line2x modes for 480i force you to use the OSSC’s bob deinterlacing, whereas I prefer sending interlaced to the TV so it can do its own interpolation that appears cleaner, though with some color distortion during movement. The clarity difference is due to there being less upscaling interpolation done to the image which now has a doubled horizontal resolution, similar to what happens for line2x mode, but only half way since line2x doubles both resolution axis.

So TX DVI mode appears to inadvertently do what I’ve always wanted; line2x for 480i without using the OSSC’s bob deinterlacing. And yes, the clarity improvement is noticeable. I do still have to use SD LPF to minimize noise for the PS2, while I’m able to use HDTV LPF for my Xbox. Not entirely sure why as I’ve used different outlets with the same results so it’s probably to do with the PS2s internal power filtering. But even still, the 480i picture looks quite good in DVI mode. I would ultimately like to have a 1280x960i line2x (no-bob) option implemented, and whatever the DVI mode is doing to also have its own option (1280x480i “half” line2x mode?).

[Zacabeb]

This probably has to do with lower resolutions in HDMI (below 27 MHz?) using sample repetition to double the sample clock and get a single clock for multiple resolutions and frame rates (480i, 480p, 576i, 576p all give 27 MHz at 8 bpc). When such a signal is flagged as DVI, the monitor might perceive those repeated samples as individual ones, doubling the reported and processed horizontal resolution.

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