Although I've been an AVS Forum member for many years, I very rarely comment on threads, mostly because I work for a manufacturer, and it's very easy to end up being considered the customer support for forum users.
The reality is that I don't work for marketing or PR
; I'm an engineer, and I was the architect and project manager of the autocal feature on our TVs. Scott reached out to me for some additional information for his article, and I was happy to provide it.
I'm commenting now because
suggested I wasn't aware of the CalMAN workflow, and also because Scott is having to field questions about the calibration section of his article, and that's the part I provided information for.
I personally appreciate feedback on the auto calibration feature, because it helps me to make our products better. As Scott reported, for example, we discovered an issue with flickering when calibrating Dolby Vision early on, thanks to user feedback, and we were able to fix this with a firmware update. The hardware level autocal feature has been a lot of work, but it's been a labour of love. There's more to do for sure, but I'm proud of what's been achieved so far.
With that being said, to address two comments that were made:
Originally Posted by D-Nice
Then I do not think Neil knows nor has gone through the CalMAN workflow since the end user is supposed to set the light output via the OLED light setting pre LUT creation. Please take a look at the CalMan workflow. It’s right there
The CalMAN workflow includes, as it’s first active page, a button to do a ‘Full DDC Reset’. This is before the first luminance measurement, and its purpose is to ‘zero out’ or more accurately, to put the TV into a full ‘bypass’ condition by doing the following:
- Load bypass 1D LUTs for Red, Green and Blue
- Load a bypass 3D LUT
- Set the 3x3 matrix to unity
- Ensure that the De-Gamma & Re-Gamma LUTs either side of the 3x3 matrix are disabled
- Set Brightness to 50 (bypass)
- Set Contrast to 85 (SDR with super white preserved) or 100 (HDR which has no super white)
- Set Colour Saturation to 50
After the Full DDC Reset, the white point will be ‘panel native’, and around 10,000 K. The next page asks the user to set a luminance using the OLED light control. I’d advise users to set this around 15% higher than the desired end luminance, because luminance will certainly drop when moving the white point to D65.
The next page is the 1D LUT calibration, which results in a luminance drop because the white point is moved in this process.
Following the 1D LUT calibration, the next page asks the user to check the peak luminance again, and adjust as needed to meet the desired target white point. This page is here precisely because the luminance is expected to have dropped.
Following this, comes the 3D LUT page, and after that, the validation pages. Obviously, there shouldn't be any luminance drop from the 3D LUT.
In conclusion, as was said previously, the 1D LUT shifts the white point from panel native to D65. A luminance drop is known and expected behavior, it's also unavoidable regardless of software if you start from panel native.
The luminance drop is handled in CalMAN by having two pages in the workflow where luminance is adjusted. It’s not a secret, we're very open about it.
Originally Posted by D-Nice
Low level blocks??? I tink you were provided incorrect info. CalMAN has access to the 1D and 3D LUT container in the panel, nothing more.
The API for calibration is not public, so there is no way anyone outside of Portrait and LG would know what low level blocks were able to be controlled. Looking at what CalMAN is doing at a high level it might seem that only the 1D and 3D LUTs are being accessed, but that's not the case, and some of this is obvious if you dig a little deeper.
As I mentioned above, the following functions are being used in the current public build of CalMAN:
- 1D LUTs for Red, Green and Blue
- 3D LUT
- 3x3 Matrix
- De-Gamma & Re-Gamma LUTs either side of the 3x3 Matrix
- Colour Saturation
- OLED Light
In addition to these, there are several other functional blocks in the video pipeline that the API covers, and CalMAN has access to. These aren’t required for a typical calibration, but the access is there.
It's worth noting that all of the functions that are controlled, are hardware features of the Alpha 9 (and Alpha 7) SoCs, with the exception of OLED Light, which is an OLED panel gain control and is therefore separate from the video path.
In summary, it certainly isn’t only 1D and 3D!