Odd dissolves in animations (Simpsons, Family Guy, HD only?)

Just wondered if anyone had any ideas on this. I've noticed odd dissolves cropping up in Family Guy episodes on BBC Three HD, and now there's been one in The Simpsons today (Channel 4 HD) at about 8 minutes in, just before Skinner says "Ralph! You're not a kangaroo!", and another quick one when Lisa is looking through Marge's scrap book at about 14 minutes in (just after the break)

It occurs where you'd expect a pan or a zoom in/out to/from something in the background - this was the case with The Simpsons today, as there seems to be one frame of panning before the dissolve begins (and the A side of the dissolve seems to freeze). I've never seen it on live action.

I've just checked the SD broadcast on Channel 4 +1 and the dissolve didn't occur - there was a pan/zoom as expected. I'd guess it's something a broadcast encoder is doing, or it could be something my YouView box defaults to doing when it gets confused?

Now I think of it, wasn't there something a few years back about encoder improvements specifically to make dissolves look nicer? Maybe something's triggering that accidentally... though that seems unlikely.

This is via DTT , I suspect it could be an artefact (perhaps coding, perhaps the way your model of receiver deals with it) of the dynamic GOP level P/I switching that all HD channels on both PSB3 and COM 7 use.

Some receivers don't/didn't cope too well with switching states, for instance Sony receivers had an audio click everytime (potentially every 12 frames) there was a switch, Sony fixed that with a s/w update. Also, check any overscan disabling you may have set relates to both p and i modes. Again, Sony receivers require the '1:1 pixel map to be made for both modes, and you can only set when the TV is forced into one or other mode <rolls eyes>

I noticed this recently on Channel 4 HD on Sky - I just presumed it was a bad edit.

I've noticed this too with Family Guy on BBC Three HD through Sky. Particularly in the latest series that's just aired.

I noticed this with an episode of Family Guy last night on BBC Three HD but at the time I just assumed it was some weird edited bit by the BBC and didn't think anything else of it until I saw this thread.

I'm guessing if it is i/p related the animation is progressive but the mixes are done in the interlaced domain, so flip the encoders to interlaced for the duration of the mix? (+/- a GOP)

My TV used to freeze for a frame when there's the mix through from the BBC news titles (progressive), to the live presenter shot, doesn't seem to any more, so perhaps there's been a software update, though often the encoder will stick in progressive mode a few seconds into the interlaced content, if it's particularly free of any sudden movement.

My current (6 year old) Sony TV has a pretty poor de-interlacer which applies uniform de-interlacing across the entire image and is a bit slow in detecting global i/p changes. (This is fed via HDMI from an external DVB-S2 receiver - which is permanently 1080/50i - I don't believe i/p switching is used on satellite services?) I don't get this when de-interlacing externally on a PC with decent de-interlacing algorithms.

You believe correctly, I think ?

My understanding is that all the major DVB-S/S2 HD services use constant 1080i encoding, with only the Freeview HD using the dynamic, encoder-decided, i/p switching (the broadcast chain upstream is still entirely 1080i - with any 1080p content psf)

my fta box always says 1920x1080i so I guess this is the case on satellite.