Question Samsung 40MU6400 - repeated 25/50 fps judder on mostly static video - changing deinterlacing mode?


Standard Member
I've just unboxed a new 40" Samsung 40MU6400, calibrated for colour and disabled all of the picture processing.

As with all other Samsung TVs I've set up, picture is Movie with Warm2, picture fit enabled. Auto Motion Plus is disabled. Digital Clean View is disabled. Film Mode is off.

Watching BBC One HD this evening, during Question Time (mostly static shots with small amounts of limited motion), I noticed that the TV was mistakenly interpreting the picture content as still image or filmic content. For whatever reason, this changes the kind of deinterlacing the display performs.

It also does it a lot on panel show programmes and game shows - The Chase (which I don't watch but the girlfriend enjoys!) suffers badly from this. Any shows that are produced as 25 progressive scan frames, but with 50i titles, make it very obvious too: the TV changes its deinterlace method half a second behind the change of picture content.

It flicks, without warning, from a bob-style deinterlace (with the correct, smooth, "soap opera" style deinterlace of 50 fields per second) to a wrong, blend-style deinterlace ("film" style, with what looks like 25 fields - like 25 progressive scan frames) and causes visible juddering on objects in motion, be it faces talking, hands waving etc.

Most annoyingly, as soon as there's sufficient movement in the picture to kick the TV into deinterlacing correctly, the picture changes back from 25 fps to 50 fps mid-scene. It'll flick back and forth many times.

It seems almost like the image processing has some kind of timeout after a motion threshold is reached; it seems to flip back if there's no more motion which passes its threshold, either of complexity or percentage of screen coverage. I'm not sure which. Perhaps it's trying to be clever and is analyzing the transport stream to try and detect flags and control deinterlacing based on that. Either way, it seems to be confused.

It's been happening repeatedly during this programme and it's utterly infuriating.

Previously I've been able to stop Samsung TVs from doing this kind of thing by labelling the source as PC which does things like disable global dimming and all image processing. However this TV is using its integrated DVB-S decoder & integrated coax input - I can't relabel the input.

This constantly switching deinterlacing is incredibly distracting and very noticeable. I've upgraded to the latest firmware, and update it whenever latest FW is available, but it's not fixed it. I've seen other recent model Samsung TVs do this too.

Anybody got any idea how to defeat this stupid behaviour on a supposedly premium display?
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