Guide to Display Cables / Adapters (v2)

[Glenwing]

6 minutes ago, el_murdoque said:

Is it possible to use an adapter from Display Port to HDMI?

Does the current guide not answer this?

[roky]

Will there ever be an adapter that supports DP output from PC and HDMI input, 4k@120hz and G-Sync? 

[conankunkid]

Can you add DP 2.1 and Thunderbolt 4 into the list? Wanna see the bandwidth to drive Samsung 57" DUHD that comes with DP 2.1.

[Glenwing]

32 minutes ago, conankunkid said:

Can you add DP 2.1 and Thunderbolt 4 into the list? Wanna see the bandwidth to drive Samsung 57" DUHD that comes with DP 2.1.

All transmission modes in DisplayPort 2.1 are already present. There haven't been any new speeds introduced since version 2.0. Likewise display capabilities have not changed between Thunderbolt 3 and 4.

[KidKid]

Thanks! This is really helpful.

[onegoodberger]

On 5/31/2024 at 1:16 PM, Glenwing said:

All transmission modes in DisplayPort 2.1 are already present. There haven't been any new speeds introduced since version 2.0. Likewise display capabilities have not changed between Thunderbolt 3 and 4.

For DP 2.1 - you have DP80/UHBR20 but you could theoretically add DP54/UHBR13.5 (52.22 Gbit/s) 
Thunderbolt 5 and USB4 also have a 120Gbps "bandwidth boost" mode which I guess would be 116.07 Gbit/s?  

[Glenwing]

6 hours ago, onegoodberger said:

For DP 2.1 - you have DP80/UHBR20 but you could theoretically add DP54/UHBR13.5 (52.22 Gbit/s) 
Thunderbolt 5 and USB4 also have a 120Gbps "bandwidth boost" mode which I guess would be 116.07 Gbit/s?  

I think all transmission modes are listed. Which section are you referring to?

[onegoodberger]

On 6/5/2024 at 8:45 PM, Glenwing said:

I think all transmission modes are listed. Which section are you referring to?

The reference table in the Data Rate / Maximum Refresh Frequency Calculator section is one. The other would be the Thunderbolt table in the Maximum Refresh Frequency and Resolution of Everything.

[Glenwing]

25 minutes ago, onegoodberger said:

The reference table in the Data Rate / Maximum Refresh Frequency Calculator section is one. The other would be the Thunderbolt table in the Maximum Refresh Frequency and Resolution of Everything.

In the max data rate reference table right now it's organized by standard, with the max that each is capable of... technically it's correct as-is although it may not be the best approach. But the list gets quite long otherwise. "HDMI 2.1" would also need to be broken up into its 6 different speeds.

[Platos]

I think the calculator calculates 10bit DSC wrong.

As far i know DSC does always use specific bitrate/pixel and not specific compression ratios.

See here: https://www.rambus.com/blogs/vesa-display-stream-compression-dsc-the-complete-guide/
Or here: https://vesa.org/vesa-display-compression-codecs/

So that means it is impossible to have a 3.0x ratio with 10 bit as far as i know. So it should not be possible to choose 3.0 DSC ratio, when we take 10bit and also there should be the right ratio (3.75x) for 10bit. If that is not possible (to grey out some settings, if you take 10 bit), then maybe you better display bitrate/pixel instead of a ratio and then calculate internal differently for 10bit.

Maybe im also wrong with that, but the linked sources say it is a 3.75x ratio and the source is vesa itself.

[Glenwing]

34 minutes ago, Platos said:

As far i know DSC does always use specific bitrate/pixel and not specific compression ratios.

See here: https://www.rambus.com/blogs/vesa-display-stream-compression-dsc-the-complete-guide/
Or here: https://vesa.org/vesa-display-compression-codecs/

 

This is correct in terms of how it works internally. At the time I wrote this calculator I decided to allow the user to select a specific ratio instead and the corresponding bit rate would be used for calculation.

44 minutes ago, Platos said:

So that means it is impossible to have a 3.0x ratio with 10 bit as far as i know.

DSC can compress to any number of bits per pixel above 6 in steps of 1/16. You can have a 3:1 ratio with 10 bpc color depth (30 bit/px) by choosing 10 bit/px as your target.

46 minutes ago, Platos said:

when we take 10bit and also there should be the right ratio (3.75x) for 10bit.

A 3.75:1 ratio would be if you used 10 bpc (30 bit/px) image and compressed it to 8 bit/px. Which you could do, but I'm not doing that, when you select the "3.0x" option it selects the compression parameters that will give that ratio, which is 10 bit/px output for 10 bpc input.

 

Technically it is the 2.5x ratio that might have some inaccuracy, as a 2.5x ratio at 8 bpc color depth is 9.6 bit/px, but closest possible selection is 9.625 bit/px. So maybe I should have selected a more composite number like 2.4x

 

Anyway there are some improvements that could be made, and just letting the user select the ratio may not have been the best way, but that's how it is for now.

[Platos]

Thanks for your answer. Then the 3.0x ratio is not wrong, thanks for clarification.

 

But then, if 6bit/pixel is possible, it should be possible to use a 5.0x ratio, right?

And about uneven bit/pixel: Do you think any monitor-manufacture would use sth like "9.625 bit/pixel" ? I mean would any manufacture use such numbers or is there a high chance, that they use even numbers like 6,7,8,9,10 bit/pixel ?

 

Because technically with a 9bit/pixel ratio it would be possible to run 8k 10bit @ 240Hz. Or at least there could be a 10 bit 8k120Hz Moitor or TV with a 2.0x ratio or with a slightly higher ratio also 144Hz.

[Glenwing]

3 hours ago, Platos said:

Thanks for your answer. Then the 3.0x ratio is not wrong, thanks for clarification.

 

But then, if 6bit/pixel is possible, it should be possible to use a 5.0x ratio, right?

HDMI and DisplayPort both mandate a lower limit of 8 bit/px except when chroma subsampling is used, which is not common (at least for monitors). Yes higher ratios are possible in terms of the algorithm will still work, but may not maintain a level of quality that passes testing for "visually lossless" anymore so generally there will be further restrictions in the specific application (i.e. HDMI and DisplayPort specs) beyond what the DSC standard itself provides.

3 hours ago, Platos said:

And about uneven bit/pixel: Do you think any monitor-manufacture would use sth like "9.625 bit/pixel" ? I mean would any manufacture use such numbers or is there a high chance, that they use even numbers like 6,7,8,9,10 bit/pixel ?

Yes, HDMI for example specifies that 8K 60 Hz should use 9.9375 bit/px DSC for a 24G link. Ideally you should compress just the amount you need to fit within the available bit rate to minimize the loss in quality.

 

DisplayPort on the other hand doesn't have any pre-defined values, it just mandates a minimum requirement is 8 bit/px to 16 bit/px in steps of 1 bit/px must be supported. Fractional values are allowed but may not be supported by all devices, in which case the next lowest mode supported by both devices would be used.