Devices > Video Cards, Monitors, Televisions, and Projectors
Dropouts when bitstreaming Atmos through an HDMI 2.1 AVR with nVidia 3xxx GPUs
SamuriHL:
My HTPC is currently off at the moment. If I have time I'll maybe mess around with it this week. I have the 3080 in it as I don't have a way to throw the 4080 in yet. At some point, maybe by Christmas, I hope to get a new mobo and CPU to rebuild my proper HTPC and put the 4080 in it.
Manni:
--- Quote from: SamuriHL on August 14, 2024, 09:05:54 am ---My HTPC is currently off at the moment. If I have time I'll maybe mess around with it this week. I have the 3080 in it as I don't have a way to throw the 4080 in yet. At some point, maybe by Christmas, I hope to get a new mobo and CPU to rebuild my proper HTPC and put the 4080 in it.
--- End quote ---
Thinking about it using the TDMS downscale on the VRROOM will most likely not work, as the whole point of it is to allows the source to send the full-fat 8K signal to the VRROOM so that you can pass it through to TX0 and so that it can be downscaled for a secondary display on TX1.
What you need is for the GPU to be limited to TDMS, so that it doesn't use FRL5/6 at all. For this, you need a HDMI 2.0 switch, a HDMI 2.0 EDID or the AVR to limit the bandwidth to HDMI 2.0 (if you're going through the AVR, I don't think you are).
SamuriHL:
I'm definitely not going through my AVR, no. I suppose I could force it with an EDID in the VRROOM. I'd rather just get my new system built but money and the fact that the mobos and cpu I want aren't out yet.
MarcVRML:
I worked around this problem by using both a high quality HDMI 2.1 cable and then setting GPU clocks so that they don't downclock all the way.
I noticed this as when I was gaming (clocks all running high), the dropouts didn't happen. Watching video though (clocks low, minimal GPU requirement), the problem was frequent.
By setting my memory clock minimum to 810 instead of 405, this runs the card on an extra 4W of power, and generates an additional 1C of heat, so negligible impact, but appears to have fixed the problem.
Depending on your GPU, the numbers and ranges may differ so some experimentation is likely needed if anyone’s reading this with the same problem, but the method’s pretty simple :
— Determine compatible clock speeds
Open an admin command prompt and type this command:
nvidia-smi -q -d SUPPORTED_CLOCKS
This’ll give you a long list of memory MHz speeds, and within each of those, a range of compatible GPU clock speeds. Ignore the batch of timings at the bottom of the list – those are the slowest downclocks which we don’t want as they cause the problem. For me, next group up is the batch for 810MHz.
Make a note of the memory clock batch number (810 in this case). This is your minimum memory clock.
Now make a note of the minimum gpu clock speed within that batch (it’ll be at the bottom. For me it’s 210).
So that’s your minimums. Now for the maximums.
Go to the top of the list for the fastest supported values. For me this is a memory clock of 10501MHz and a Graphics clock of 3240MHz.
Now you’ve got enough for these commands (which if you like you can also put into a BAT file and run as part of your startup routine).
The -lgc flag controls min,max values for graphics clock, and the -lmc for memory clock.
nvidia-smi -lgc 210,3240
nvidia-smi -lmc 810,10501
This will allow the GPU to ramp up clock speeds when it thinks it needs it, but it’ll stop it downclocking below the threshold required to supply steady signal through the HDMI.
Hope this is helpful!
Manni:
--- Quote from: MarcVRML on August 16, 2024, 08:14:48 am ---I worked around this problem by using both a high quality HDMI 2.1 cable and then setting GPU clocks so that they don't downclock all the way.
I noticed this as when I was gaming (clocks all running high), the dropouts didn't happen. Watching video though (clocks low, minimal GPU requirement), the problem was frequent.
...
--- End quote ---
Thanks, that's very helpful and I might give it a try when I'm back from holiday in two weeks.
However, I can't see how the GPU could behave differently when using a HDMI 2.0 input and a HDMI 2.1 input, when both are playing 4K23 10bits RGB content within TDMS bandwidth, and I get drops with the HDMI 2.1 input and no drops with the HDMI 2.0 input.
Please could you kindly provide all the information listed in the first post, so that we can know more about your setup?
Also, surely this isn't relevant when using max performance power in nVidia, and I still get drops with that setting.
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