Originally Posted by ithaca
-- When switching from HD (1080i) to SD (480i), there is a 2-3 second pause before the picture comes up. All of my Comcast DVRs have done this in the past so I've always assumed this is normal but I figured now would be a good time to confirm
-- When switching from SD to HD, there is about a 5 second pause and the box displays DUI (DVI?) on the front panel. Once the picture comes up, there is an additional 2 seconds without any audio.
Depending on your HDTV, the time to change resolutions and handle the HDMI re-handshake can vary.
Since you've got your DVR set to "1080i" rather than "native", the DCX3400 itself is not changing outgoing HD resolutions between 720p and 1080i. But when you go to an SD channel at 480i, that would trigger a resolution change on your HDTV and an HDMI re-handshake.
As far as how quickly audio and video return during this resolution transition, well again it's up to your HDTV. My Sony 34XBR960 does it fairly quickly, usually 1-3 seconds.
In my case, with "native" set, I see this same situation when going from any 720p HD channel to any 1080i HD channel. With "native" there is another small time delay component as the DCX3400 itself must change resolutions. Again, my 960 handles it quite quickly and the whole process (including DCX3400 change) still takes 1-3 seconds. In the meantime, there is black screen and no audio. Video may return before audio, or vice versa.
So I'd say your situation is "normal".
NOTE 1: even with "native", when changing between two 720p or two 1080i channels, there is ZERO delay. And in your case I would suspect you see no delay in switching between two 480i channels, and between any 720p/1080i channels. There should be no loss of picture or audio if there is no resolution change sent to the HDTV, and thus no re-handshake required. So this whole symptom you're describing is (a) normal, and (b) goes as quickly as your HDTV can itself change resolutions, in your case between 480i and 1080i because you have "1080i" set on your DCX3400 instead of "native" (which would have added 720p to your resolution mix).
NOTE 2: as was mentioned above by another poster, you might consider going to "480: OFF" if you don't want horizontal stretching of 4:3 content, but would prefer true 4:3 images in a 4:3 area centered on the 16:9 screen, with black pillar bars on left and right. This also might help reduce transition times from 1080i to 480i. Also, with HDMI set to "native", "480" is grayed-out and is forced to "OFF".