Adding a complete image path/feature cross-switch would be possible but very expensive FPGA resource wise, so I would prefer to select in advance which path can apply what features.
For example, if we dedicate one output for recording, that this output shouldn't have to handle any features or overlays.
Lets first create a usage scenario list how the 3 outputs might be used (even the wild configurations):
I'll start with what comes to mind but please feel free to add other ideas as well:
Situation 1:
HDMI 1: cleanfeed for recording (LUTs)
HDMI 2: viewfinder (LUTs, overlays, peaking, false colors, look around, etc.)
HDMI 3: assistant or director monitor (LUTs, overlays, peaking, false colors, look around, etc.)
Situation 2:
HDMI 1: experimental RAW out 1
HDMI 2: experimental RAW out 2
HDMI 3: viewfinder (LUTs, overlays, peaking, false colors, look around, etc.)
Situation 3:
1080p 180FPS high speed recording with 3 recorders:
HDMI 1: cleanfeed for recording (LUTs) every 3rd frame A
HDMI 2: cleanfeed for recording (LUTs) every 3rd frame B
HDMI 3: cleanfeed for recording (LUTs) every 3rd frame C
Those sound plausible to me. However, I do want to throw one thing out there: the Atomos Shogun has an HDMI 1.4b board in it. According to the specs this allows it to accept 4K HDMI signals and HD signals at up to 120fps.
Would an alternate option be to use an HDMI 1.4b or possibly even HDMI 2.0 board (if one is available) to output the experimental Raw and high speed signals from a single HDMI port?
I'm making this suggestion as it would be much more efficient financially, physically and technically to have to rely on just one recorder (albeit a relatively expensive one) than having to use three.
Alternatively it might be better to save the high speed and Raw modes for SDI shields as these seem to allow much higher data rates even with just 3G SDI (let alone 6G or 12G).
We plan to have two different HDMI shields, one with 3 ports and one with a single port (maybe 2 ports if we have enough bandwidth) which will allow for higher pixel clocks and thus larger formats.
It might be easier to produce just one shield that has one 1.4b HDMI (for high speed or 4K) and two 1.0 ports for monitoring.
We have about 16Gbit/s bandwidth to the shield, doing the math explains why this isn't really "easier" :)
HDMI 1.0 = 3.96 Gbit/s [4.95Gbit/s TMDS]
HDMI 1.4 = 8.16 Gbit/s [10.2Gbit/s TMDS]
3 x HDMI 1.0/1.1/1.2 = 11.88 Gbit/s [14.85 Gbit/s TMDS]
1 x HDMI 1.4 + 1 x HDMI 1.0 = 12.12 Gbit/s [ 15.15 Gbit/s TMDS]
1 x HDMI 1.4 + 2 x HDMI 1.0 = 16.08 Gbit/s [ 20.10 Gbit/s TMDS]
I don't see why not - you could simply disable one of the HDMI 1.0 ports when running the HDMI 1.4 port 'hot' (as it were) - i.e. If it is used for Raw, 4K or high speed output. If it's just used for HD only the bandwidth would be the same as if it were HDMI 1.0 - but you'd have the extra bandwidth when needed and the extra output when you don't - surely it's the most flexible option?