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The real "fun" starts with HDR. See, HDR on one hand requires ten bits of color per channel. So bandwidth wise 4K @ 60Hz 10 bit fits DisplayPort 1.2 but not ev

by chx 7y ago

The real "fun" starts with HDR. See, HDR on one hand requires ten bits of color per channel. So bandwidth wise 4K @ 60Hz 10 bit fits DisplayPort 1.2 but not even HDMI 2.0 has enough. See the calculator https://linustechtips.com/main/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=3840&V=2160&F=60&bpc=10&timing=cvtrb&calculations=show&formulas=show https://linustechtips.com/main/topic/729232-guide-to-display... But! HDR is more and some video standards have the necessary extensions but it can also be done from software but then only compatible software will be HDR. Check https://superuser.com/a/1335410/41259 https://superuser.com/a/1335410/41259 > The HDR mode will automatically activate if the monitor receives a compatible signal, but the device only relies on a software-based implementation. When active, the HDR representation adds a nice touch of extra color pop and a seemingly deeper contrast range, although the monitor’s limitations will come into play here. And this extra has been added to HDMI 2.0b (compared to HDMI 2.0a) and for this reason it is said HDMI 2.0b support 4k @ 60Hz HDR when it can't because it doesn't have enough bandwidth (well, it does for 4:2:0) and DisplayPort 1.2 is said to not support it when it does have enough bandwidth. Oh joy.

ksec 7y ago
How does 120 or 240 or even 360Hz Monitor works? Because at 4K, 10BPC, 240Hz is already ~70Gbps, pushing close to the DisplayPort 2.0 limit. I know there is DSC compression, but seriously who want a compress link especially when it is not true lossless.
- phonypc 7y ago
  AFAIK there are no consumer monitors that do 4k at >144Hz. 200Hz+ are all 1080p.
  - wincy 7y ago
    The state of the art, at least at consumer levels, uses an FPGA to do image processing, and has a fan to cool it (that many people complain about), is here[0]. 144hz over displayport. I also don't think it can do full HDR 4:4:4 at that refresh rate. [0] https://www.amazon.com/Swift-PG27UQ-G-SYNC-Gaming-Monitor/dp/B07F1VGGLK https://www.amazon.com/Swift-PG27UQ-G-SYNC-Gaming-Monitor/dp...
    - zlynx 7y ago
      No it can't. Which is why I run mine at 98 Hz.
    - amarshall 7y ago
      It can’t even do non-HDR uncompressed at 4K UHD 144 Hz. Max uncompressed is 120 Hz. That’s all DP 1.4 can do.
    - ksec 7y ago
      Thanks, I think will need to read up on that. Were the processing the limitation? Or was it DisplayPort?
Latty 7y ago
Yeah, it's kinda sad how close we are to the specs and that they aren't getting much ahead. Higher resolutions just chew through that bandwidth quickly. Apple had to really hack around to get the Pro Display XDR to do 6k at 10-bit at 60Hz. They are using USB-C w/Thunderbolt for that and actually pushing two DisplayPort 1.4 signals down that cable. Clearly cludgy at best. Even then at 6k/10-bit/60Hz the other USB-C ports on the monitor can only work at USB 2.0 speeds because the link is so saturated. 6k/10-bit is a bit niche right now for sure, but I'd sure love to be able to daisy-chain my three 4k monitors which I can't do, and 120Hz is becoming very mainstream (although actually rendering 4k/120Hz is problematic on the graphics card side too).
- chx 7y ago
  I believe Apple arrived to the Prod Display resolution based on the Thunderbolt bandwidth! https://linustechtips.com/main/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=6016&V=3384&F=60&bpc=10&timing=cvtrb&calculations=show&formulas=show https://linustechtips.com/main/topic/729232-guide-to-display... it's 38.70 gbit/s which is suspiciously close to the bus bandwidth limit of 40 gbit/s
  - amarshall 7y ago
    It also is the equivalent PPI of the Apple Cinema Display (which was 2560x1440 27”), but 2x for “retina” monitors. I eagerly await DP 2.0 to become widespread so the rest of the world can catch up to the XDR and LG UltraFine 5K.

by chx 7y ago

ksec 7y ago

How does 120 or 240 or even 360Hz Monitor works? Because at 4K, 10BPC, 240Hz is already ~70Gbps, pushing close to the DisplayPort 2.0 limit. I know there is DSC compression, but seriously who want a compress link especially when it is not true lossless.

phonypc 7y ago
AFAIK there are no consumer monitors that do 4k at >144Hz. 200Hz+ are all 1080p.
- wincy 7y ago
  The state of the art, at least at consumer levels, uses an FPGA to do image processing, and has a fan to cool it (that many people complain about), is here[0]. 144hz over displayport. I also don't think it can do full HDR 4:4:4 at that refresh rate. [0] https://www.amazon.com/Swift-PG27UQ-G-SYNC-Gaming-Monitor/dp/B07F1VGGLK https://www.amazon.com/Swift-PG27UQ-G-SYNC-Gaming-Monitor/dp...
  - zlynx 7y ago
    No it can't. Which is why I run mine at 98 Hz.
  - amarshall 7y ago
    It can’t even do non-HDR uncompressed at 4K UHD 144 Hz. Max uncompressed is 120 Hz. That’s all DP 1.4 can do.
  - ksec 7y ago
    Thanks, I think will need to read up on that. Were the processing the limitation? Or was it DisplayPort?

Latty 7y ago

Yeah, it's kinda sad how close we are to the specs and that they aren't getting much ahead. Higher resolutions just chew through that bandwidth quickly. Apple had to really hack around to get the Pro Display XDR to do 6k at 10-bit at 60Hz. They are using USB-C w/Thunderbolt for that and actually pushing two DisplayPort 1.4 signals down that cable. Clearly cludgy at best. Even then at 6k/10-bit/60Hz the other USB-C ports on the monitor can only work at USB 2.0 speeds because the link is so saturated. 6k/10-bit is a bit niche right now for sure, but I'd sure love to be able to daisy-chain my three 4k monitors which I can't do, and 120Hz is becoming very mainstream (although actually rendering 4k/120Hz is problematic on the graphics card side too).

chx 7y ago
I believe Apple arrived to the Prod Display resolution based on the Thunderbolt bandwidth! https://linustechtips.com/main/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=6016&V=3384&F=60&bpc=10&timing=cvtrb&calculations=show&formulas=show https://linustechtips.com/main/topic/729232-guide-to-display... it's 38.70 gbit/s which is suspiciously close to the bus bandwidth limit of 40 gbit/s
- amarshall 7y ago
  It also is the equivalent PPI of the Apple Cinema Display (which was 2560x1440 27”), but 2x for “retina” monitors. I eagerly await DP 2.0 to become widespread so the rest of the world can catch up to the XDR and LG UltraFine 5K.