OSX dithering - Help wanted
Looks like I got the KEXT injector working on El Capitan 
Can't speak for the dithering part though.
Should work:
- AMD
- NVIDIA
Probably won't work without patching
- Any Intel Graphics chip
martin The dithering itself hasn't been fixed.
All that's been done is I managed to sort out the KEXT injection itself. Still some way to go.
If I get a second computer setup (doesn't necessarily have to be a Mac I can do live debugging which should let me check if the dithering is being turned off by the driver, etc.)
If anyone has an OS X machine with an Nvidia GPU and possibly has dithering "sensntivity" I might have a working Nvidia injector working for you on short notice. No promises though.
Gurm Well. I don't think that's going to be an issue.
Unlike nVidia Optimus the switchable graphics on Macbooks are fundamentally different. According to an Apple display engineer I spoke with a number of years ago the switchable graphics works via a "mux chip" that's hooked up to the display and the output of the nVidia and Intel cards. It has a driver on OS X that "signals it" to switch cards when needed and it completely disconnects the screen from the Intel card and "connects it" to the nVidia card. And before you say "Well the screen doesn't turn off when switching cards". That's probably because it switches so fast it just drops a frame or two. This is 100% confirmed under Linux with raw I/O access.
Nice. What I meant was more along the lines of ... there used to be an app that let us tell the machine to ONLY use nVidia, that doesn't work under newer versions of OSX. So we'll have to figure out a way to not have it switch back to Intel.
- Edited
Gurm gfxCardStatus Ah. Can't really help you there. I still use El Capitan. Works for me.
All I'm willing to say at this time publicly is that some major technical hurdles have been overcome, with regards to the framework needed for injecting the code for disabling the dithering in the AMD/Nvidia kexts under OS X, but it's not done yet.
diop Will Intel be a possibility in the future? Or could the ditherig tool be ported over to OS X?
If someone makes a Linux version of the dithering tool, it might be possible for it to work under OS X. Again, not making any promises here.
Looks like a UK Apple Service Provider either re-sell or are involved with AHK as I discovered this post.
Link: https://www.jigsaw24.com/news/amulet-hotkey-fix-temporal-dithering-for-latest-macos
"If you're using Amulet Hotkey for KVM over IP, be warned that installing the latest version of macOS on your endpoints automatically re-enables temporal dithering.
This vastly increases the amount of information you're forced to handle over IP and, as a result, will have a negative impact on the quality of your image.
Happily, Amulet Hotkey are already aware of the issue, and have released a kernel extension that allows you to disable temporal dithering at the driver level, regardless of which version of macOS you're running. (If you're running an earlier version of macOS or OS X, the fix should already be in place – contact us if you find this isn't the case.)
The usual caveats apply: the fix will only work with Amulet hardware and software, not with that from third parties; the kext itself is not available publicly – in a delightfully cloak-and-dagger scenario, you need to get in touch with our team on the details below, and they'll send you a temporary download link and instructions for how to install it."
I'm hoping at some point we can disassemble or hack Amulet's driver. I think it's pretty frustrating that a solution exists but we can't use it!
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Gurm I agree it's frustrating. We should petition Apple to allow us to do this...if we can't get through via support, maybe we can find engineers at Apple on LinkedIn or similar and try to make them aware of this issue. Most people are under the impression that dithering is not perceptible by humans, but as we know, it can still have an adverse affect on us.
I don't use OS X and I don't know much about Kexts, so one possibility could be to use Rent-A-Coder or something like that, and maybe pay someone that has the experience to make one for us (and make sure we get the source code). I'd be happy to chip in for this for our community. As JTL mentioned in another thread, disabling dithering is a competitive advantage for the Amulet folks, unrelated to eye strain.
The fact that it can be done on OS X is very encouraging. I don't know if iOS is known to dither, but it's very locked down, and I strongly suspect it's not possible to disable or alter without jailbreaking.
Came across this, don't know if it'll make an improvement for us:
https://techcrunch.com/2018/03/30/macos-finally-gains-external-gpu-support/