[joevt]

Since DisplayLink makes the driver, you should talk to them.

One question I have: is the 5140×2880 resolution only for dual cable displays (dual DisplayPort 1.2 connection)? In other words, it’s actually two 2560×2880 signals.

The only reason I can think of why they might not be able to support 5120×1440 (even though the pixel clock and resolution is less than that of 4K) is because they have some silly 4K limit (2^12) on the width.

Can you post the EDID? You can get that by using Monitor Asset Manager (moninfo.exe). Select the text and copy it into a text file. Just the hex bytes would be sufficient.

[joevt]

Add your vote to https://support.displaylink.com/forums/287786-displaylink-feature-suggestions/suggestions/38503027-add-support-for-5120×1440-resolution

The CSV-1460 has the DL-6950 DisplayLink chip. If it can support 4096×2160 then it should be able to support 5120×1440 (fewer pixels).

Did you try downloading the latest drivers 9.3 M0?
https://www.displaylink.com/downloads/file?id=1485

I found release notes for 9.0 M2 that mentions (but does not describe) a change for 5120×1440 made in 9.0 M0.
http://webcache.googleusercontent.com/search?q=cache:T9gzKodpwMwJ:assets.displaylink.com/live/downloads/release-notes/f1314_DisplayLink%2BUSB%2BGraphics%2BSoftware%2Bfor%2BWindows%2B9.0%2BM2-Release%2BNotes.txt+&cd=2&hl=en&ct=clnk&gl=ca&client=safari

 

[joevt]

Looks like Club 3D has finished their DisplayPort 1.4 MST hub, the CSV-7300.

StarTech has also announced one (MST14DP123DP). It looks identical to the Delock-87737.

Does the CSV-7300 use the same Synaptics VMM5330 chip as the StarTech and Delock?

What does the following statement mean? Or what should I take away from knowing that the CSV-7300 has this feature? What’s a slice? Is there a 3 or 5 slice decompression? What’s the difference?
“DSC 1.2 transport and up to 4-slice decompression”

The reason I ask, is because there is something I don’t understand about the supported combinations of resolutions. For example, as far as I know, 8K30 24bpp only requires HBR3 (non DSC). If DSC has a 3:1 compression ratio, then shouldn’t two or three of those be allowed?

The specification sheet has the following asterisk note:
“*Requirement: – Host must support DP1.4 with DSC1.2 feature”

The asterisk seems to apply to all the resolutions but this is unclear because the asterisk is in the middle of every resolution like this “3840×2160*60Hz, 24bpp”. I think you need a separate table for non DSC? But you have the table above that which should be sufficient but it neglects to show the bits per pixel and it’s missing the 8K30 option. The table with heading “DP1.4 Output Port 1, DP1.4 Output Port 2, DP1.4 Output Port 3” and showing all three combinations of connecting one or two displays is redundant if you fixup the first table and just say that displays can be connected to any output port without change in behavior.

The asterisk seems to state that the hub can’t even do a single 8K30 24bpp without DSC – even though HBR3 has enough bandwidth. Does this mean MST adds a lot of bandwidth? I know it adds some, but this seems excessive. Well, I did the calculation, assuming CVT-RB timing, an overhead of only 4.823% will make 8K30 24bpp not work. That seems reasonable. What is the actual overhead? Using CVT-RB2 timing, more than 5.9% overhead would cause 8K30 24bpp to not work.

This amount of overhead doesn’t explain why DSC only allows one 8K30 24bpp instead of two. Maybe the compression ratio is not 3:1? It doesn’t seem to be at least 2.5:1 because otherwise 8K60 24bpp would be supported. 2:1 is not enough because it only allows 4.41% overhead (using CVT-RB timing).

The tables don’t say what kind of timing is used (CVT-RB or CVT-RB2).

Does the MST hub support converting DSC to non DSC? It does not say otherwise so I assume that is true. In other words, DSC can be used on the input to allow output to more 4K60 non DSC displays than could otherwise be supported by non DSC HBR3.

I believe the MST hub can convert between different link rates and link speeds. For example, it can convert HBR3 x4 MST to dual HBR2 x4 SST to drive a dual cable DisplayPort 1.2 display like the Dell UP2715K at 5K resolution (only at 24bpp though) from a single DisplayPort 1.4 port. Or it can convert HBR2 x4 to HBR3 x2 (if you have an old DisplayPort 1.2 source and want to use a new DisplayPort 1.4 two lane adapter to its full capability).

Back to the statement in the specification sheet that says “DSC 1.2 transport and up to 4-slice decompression”. While I don’t know what a slice is, I believe that it means that the hub can transmit DSC from the GPU to a display that supports DSC, and it can decompress DSC from a GPU to a display that does not support DSC, but it cannot compress a DisplayPort signal from a GPU and and send that compression output to a DSC display. Is that correct?

Does HDCP affect the ability to decompress?

[joevt]

I don’t think there’s anything new. There are the devices from SIIG and gofanco.
https://www.amazon.com/dp/B07C39QBSF
https://www.amazon.com/dp/B07BT4BG4C

I think they’re selling the same products. Visit their websites for more info.

They both have a 1-to-1 version which are probably the same product from opto-media.
http://opto-media.com/goods.php?act=category&no=55

They both also have a 1-to-2 version that I haven’t seen before which are probably the same product from Partilink.
http://partilink.com.tw/product-info.php?id=93%20Video%20Splitter,HDMI%202.0%20to%20DisplayPort%201.2a%20Splitter%201×2

 

[joevt]

BizLink has a DP 1.4 MST Hub but I don’t know if it’s something they sell in single units:

https://www.bizlinktech.com/products/detail/1285/DP+1.4+MST+Hub

[joevt]

The Delock 87737 is a stand-alone DisplayPort 1.4 MST hub. I think it uses the same Synaptics chip that the HP Thunderbolt Dock G2 does.

https://www.delock.com/produkt/87737/merkmale.html

But it’s only sold in Europe? I guess one of those stores will ship to North America.

[joevt]

Realtek? Oh, I see there’s a post about it at 

Realtek Demonstrates RTD2173 DisplayPort 1.4 to HDMI 2.1 Converter

[joevt]

An adapter would work on the pixel level, rather than the frame level so there shouldn’t be any lag. For 4K 60 Hz: A frame is 60 Hz or 16 ms. A line is 133 kHz or 8 µs. A pixel is 533 MHz or 2 ns.

I’m not sure how much information is required by DSC. The DSC specs are freely available though. There is C source code so you can test it with various images. VESA describes DSC as a low latency, low complexity codec. Wikipedia says that for HDM 2.1, DSC is only for resolutions higher than 8K but that doesn’t mean an adapter couldn’t use DSC on the DisplayPort side.

I don’t know how an adapter will handle other features of HDMI 2.1 such as VRR (maybe convert it to DisplayPort’s Adaptive Sync?)

Most of the lag will probably come from the TV instead of an adapter. According to https://www.rtings.com/tv/reviews/lg/sm9500 , it has 13 ms input lag for 60 Hz game mode. For 120 Hz it’s 7 ms. Outside game mode, it’s up to 84 ms.

New cables will not be enough to test HDMI 2.1. You’ll also need a HDMI 2.1 source. AMD and Nvidia don’t support it yet so this is where an adapter would be useful.

[joevt]

With MST you are splitting the bandwidth. CSV-1545 allows two 4K 30Hz displays. With a CAC-1507 USB-C to DisplayPort adapter and a CSV-5300A triple DisplayPort hub, you can connect 3 Full HD displays. 

With Thunderbolt, you get two full bandwidth DisplayPort 1.2 SST signals which allows two 4K 60Hz displays.

 

[joevt]

I’ve used the DP 1.4 MST hub of the HP Thunderbolt Dock G2 using a PC running Windows 10 and having a GTX 1070 card. I’ve posted the results of my tests in a thread at eGPU.io.

The specs for the Dell UP2715K say it supports 10 bit per component color. The Nvidia control panel lets me choose 10 bpc color when using two separate DisplayPort 1.2 connections but only 8 bpc when using two DisplayPort 1.2 connections from the DisplayPort 1.4 MST hub.

If you do the math, using a 966.5 MHz pixel clock, you can see that 10 bpc exceeds the bandwidth of DisplayPort 1.4 (without DSC) but fits in the bandwidth of dual DisplayPort 1.2.

The “HP THUNDERBOLT DOCK G2 FEATURES AND TROUBLESHOOTING” technical white paper pdf says that “HP Thunderbolt Dock G2 is DSC ready”. It is unclear if this means it is support now or in the future. The next line implies now: “In order to fully support DP 1.4 DSC customers must be using a host platform that fully supports the DP 1.4 DSC”, but there is a later line that implies later: “Triple 4K @ 60 Hz when connected to DP 1.4 systems with DSC (display stream compression) – future”.

I don’t know if there are displays that support DSC (maybe 8K TVs?) or if the AMD or Nvidia graphics support DSC in their drivers.

It would be cool when the graphics card (and drivers) supports DSC, if the MST hub could accept DSC signals and output decompressed SST signals. This could allow 10 bpc dual DisplayPort 1.2 link 5K from a single DisplayPort 1.4 port instead of just 8 bpc. I don’t know if such a mode is possible or maybe it’s the default mode (or it should be) when DSC is supported – in that case the graphics card will choose to send DSC only when the bandwidth limitation of DisplayPort 1.4 requires it. If the user doesn’t want DSC then the user will choose resolutions/refresh rates/color depths that don’t require DSC.

I saw no indication in my tests that any DSC was happening (I could not exceed non-DSC displayPort 1.4 bandwidth). It may be possible that DSC is not support by the drivers, or the MST hub, or that DSC requires the displays to support DSC (all my displays are older than DisplayPort 1.4).

The specs for the GTX 1070 says 7680×4320@60Hz is supported which means that DSC is support, or that dual cable link DisplayPort 1.4 is supported (as used by the Dell UP3218K 8K display), or both methods are supported.

[joevt]

No apology necessary, but accepted. 🙂

Anyway, while an MST hub should work for 3 Full HD displays (even 4 should work, since DisplayPort 1.2 supports 4K which is four 1080p displays), I don’t think Intel graphics supports more than 3 displays, even if some of them are connected by an MST Hub.

The NUC should allow connecting 3 displays without an MST hub. This way, they can all be 4K. One display connects to the HDMI 2.0a port. Two displays can be connected to the Thunderbolt 3 port using a Thunderbolt 3 to Dual DisplayPort adapter or similar device. Strangely, their documentation doesn’t mention this feature of Thunderbolt 3, only implying that only one display is supported from USB-C (which is true for DisplayPort alt mode but Thunderbolt 3 is different). I don’t see any reason why two displays via Thunderbolt 3 wouldn’t be supported, as only supporting one would be a waste of a DisplayPort output from the Intel graphics.

 

[joevt]

The thread is titled “Recommend an MST HUB”. He asks the question “Can I use an MST Hub?”. I think he wants an MST hub.

His problem with MST (as he described) is that his monitors don’t support chaining. The article you linked talks about chaining but in the last paragraph mentions the hub option.

[joevt]

The MST signal is provided by the NUC8I7BEH which contains Intel integrated graphics supporting DisplayPort 1.2.

The MST Hub knows the capabilities of the display, and will output an appropriate SST signal.

[joevt]

I don’t understand what you mean by “MST is not supported by your Dell U2211H”. An MST hub does not output MST. It outputs SST so it doesn’t matter what the display supports. Even if there is a problem with the DisplayPort input of the display, the display can use DVI input instead. DVI displays work with MST hubs with a DisplayPort to DVI adapter.

So get a real MST Hub. 

CSV-1477 and CSV-3242HDA use DisplayLink (video over USB). Avoid them if an MST hub works.

 

[joevt]

DisplayPort 1.4 only supports 25.92 Gbps of data (50% more than DisplayPort 1.2) but has Display Stream Compression (DSC) which is required for 8K 60Hz 8bpc (RGB or 4:4:4).

HDMI 2.1 supports 42.667 Gbps and can achieve 8K 50Hz 8bpc (RGB or 4:4:4) without DSC (60Hz requires DSC). HDMI 2.1 also supports DSC though, so it can go much higher than DisplayPort 1.4.

HDR uses 10bpc.

So even though the bandwidth of HDMI 2.1 is greater than DisplayPort 1.4 (only by 65%) an adapter to convert one to the other (including DSC on both ends) would still be useful.

Is it possible to create an HDM 2.1 display that doesn’t support DSC? If so, then it would be useful for a DisplayPort 1.4 to HDMI 2.1 adapter to tell the computer that it supports DSC, then uncompress the output to the HDMI display.

 

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