[popcornmix]

ahh... you found a trick, in both cases afterwards the picture is in normal 2D mode

I'm not sure the Pi is doing anything wrong. I suspect this is a problem with the TV. Might be worth checking if a TV firmware update is possible.

Here is a comment from our HDMI expert:

Code:

The "old" HDMI spec does not specify a way of exiting 3D mode (shame on HDMI LLC). Hence some TVs will get stuck when the source is no longer sending a 3D signal. HDMI 2.x spec mandates TVs must switch back to 2D mode when the 3D side band signal is absent (basically we just stop sending VS infoframe when exiting 3D mode). I don't think there is anything the source can do other than unplug/plug back the cable or output a different format to force the TV to resync again. I'm surprised TVs will not react to the difference between full frame packing and 2D signal as the timings are different. I will expect TV not reacting to switching between side by side/top-bottom and 2D mode only. [Of course there will always be TVs which can only enter 3D mode and remember the last seen 3D mode until "no signal" and a new 3D mode is observed, which is probably the user's problem].

Now there may be some sequence of operations that could be done that would persuade your TV to switch back to 2D mode.
If I had access to a display that misbehaved I could experiment more easily. Perhaps removing hdmi output for a second, or switching to VGA mode and back might trick the TV into switching back to 2D mode.
I'll try and add a few options to the test builds to see if any work out.

But the reality is, we are outputting a valid 2D hdmi signal and the TV really should switch back to 2D mode.