[HN Gopher] When HDMI 2.1 Isn't HDMI 2.1 - The Confusing World o...
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When HDMI 2.1 Isn't HDMI 2.1 - The Confusing World of the Standard
Author : cbg0
Score : 129 points
Date : 2021-12-13 18:57 UTC (4 hours ago)
(HTM) web link (tftcentral.co.uk)
(TXT) w3m dump (tftcentral.co.uk)
| theandrewbailey wrote:
| It sounds like the marketing people who kept renaming USB 3.x Gen
| FU got hired to mess up HDMI.
| PedroBatista wrote:
| I'm a "tech guy" and I'll be in the market soon for a screen.
|
| Just the thought I'll have to learn about this while HDMI
| disaster in order to not get burned gives me anxiety.
|
| Also, never quite liked HDMI when it came out, but from what I'm
| reading they really outdone themselves during these years.
| nvarsj wrote:
| This article doesn't mention the most infuriating aspect of HDMI
| - it's not an open standard! It's a closed, proprietary standard
| that requires licensing fees and prevents any open source drivers
| from existing. This is why the Linux AMD open source drivers
| don't support HDMI 2.1 - so you can't display 120hz@4K on Linux
| with AMD.
| mey wrote:
| Quick summary, HDMI 2.0 no longer "exists", and HDMI 2.1 only
| features are now optional according to the certifying body.
| Manufactures are supposed to indicate which features they
| support.
|
| Whelp, I guess we should just stick to Display Port 1.4
| jayflux wrote:
| I see they went to the USB school of standardisation
| Roritharr wrote:
| I really wonder what is up with that. These standards become
| increasingly frustratingly complex even for people who deal
| with them daily.
| colechristensen wrote:
| It's just design by committee and long-standing efforts for
| backwards compatibility. Also the people writing the
| standards are far too familiar with them and thus a bit
| lost when it comes to making practical decisions.
|
| Whenever you make changes there will be compromises and
| someone will have reason to be unhappy.
| jjoonathan wrote:
| Cable manufacturers probably realized that the secret to
| profits lay in resisting commoditization, beat a path to
| the table, and made it happen.
| zokier wrote:
| I don't think its particularly odd that the specifications
| are supersets of old versions; indeed that feels pretty
| common in the standards world. IETF specs are maybe the odd
| ones out where you typically have to read like ten
| different RFCs to get good picture of some standard.
| mavhc wrote:
| USB 2 Full Speed = USB 1 speed
|
| This has been going on for 20 years
| errcorrectcode wrote:
| LOL. Why don't you understand superduperspeed USB 3.4.6
| 2x2x6? It's so eeeasy.
|
| And, coming soon to an Amazon app near you:
|
| _(Pack of 3) USB4 Thunderbolt 4, 98 ft / 30m, 240W charging,
| gold plated! $19.99! Free Shipping!_
|
| It's not like anyone is checking products are what they say
| they are.
| spicybright wrote:
| You can't legally call your food a hamburger if it's 90%
| meat glue and 10% cow.
|
| Can we not do the same with cables?
|
| Whoever is responsible for setting standards must be
| getting some good kickbacks from all this...
| colejohnson66 wrote:
| The people writing the standards are also the ones
| implementing it. That's the kickback. That's why every
| USB 3.whatever device suddenly became USB4 ones.
| IshKebab wrote:
| Seems kind of reasonable. DisplayPort is exactly the same -
| just because your display supported DisplayPort 1.4 doesn't
| mean it is required to support 10 bit colour, VRR, etc.
| tjoff wrote:
| Well that makes sense. Your 1080p display shouldn't be forced
| to accept an 8k signal just because the interface supports
| it.
| thaumasiotes wrote:
| I replaced my old Dell XPS laptop with a newer Dell laptop.
| The old one had been happily driving an external monitor
| through a thunderbolt cable (USB-C on the laptop side;
| DisplayPort on the monitor side.)
|
| The new laptop still has a thunderbolt port proudly
| advertised in the specs. But I'm not allowed to use it. It
| won't send video data out that way. And when I called tech
| support, the most they would offer me for my newly-purchased
| laptop was "Don't use the thunderbolt port. Use the HDMI
| port."
| kup0 wrote:
| Why does it feel like it is inevitable that
| standardization/licensing organizations in tech will always
| eventually turn into a user-hostile mess?
|
| USB, HDMI, what can we screw up next?
|
| Is it incompetence? Malice? I'd really like to see an in-depth
| investigation of this phenomenon
| rob_c wrote:
| I'm leaving towards malice (through not caring so much for
| users) caused by big tech using this arena as a battleground.
|
| I wish all cables were equal too, but c'est la vie
| errcorrectcode wrote:
| Greed, of course.
|
| If it becomes too big of a problem, each cable and device will
| be required to have a challenge-response Obscure Brand Inc.
| proprietary U9 chip burned with a valid secret key and serial
| number at the factory that must return a valid response for the
| link to be enabled.
| ASalazarMX wrote:
| HDMI was never a pro-user protocol, it was made to encumber a
| digital display signal with DRM.
| ChuckNorris89 wrote:
| This. HDMI was cooked as a proprietary connector with DRM by
| the big manufacturers in the DVD/Blu-Ray, TV, home-
| entertainment business and the big movie studios to enforce
| stronger content protections to protect their IP, at wich it
| miserably failed, as I can still torrent every Hollywood
| blockbuster and every Netflix series.
|
| IIRC, every manufacturer must pay a fee to the HDMI
| consortium for every device with HDMI they sell.
|
| DisplayPort, by contrast is a more open standard only
| requiring a flat fee for the standard documentation and
| membership instead of a fee per unit sold IIRC.
| babypuncher wrote:
| DisplayPort and DVI both support HDCP. This wasn't the
| purpose behind HDMI, though support for it was no doubt a
| requirement for adoption. It was designed to be a single
| cable for carrying video and audio between playback
| devices, receivers, and displays.
|
| For this purpose, it succeeded and did a much better job at
| it than alternatives. HDMI still makes far more sense for
| use in a home theater environment than DisplayPort thanks
| to features like ARC.
| Talanes wrote:
| HDMI is great for a home theatre set up where there's an
| obvious central unit, but the ecosystem has gotten worse
| if your speakers don't take in HDMI, at least at the very
| cheap end of the spectrum I buy on.
|
| My current TV will only put out an inferior "headphone"
| mix over the 3.5mm connection, and the SPDIF connection
| is co-axial on the tv, but optical on the speaker. Having
| to run a powered converter box just to get audio from my
| tv to a speaker feels like such a step backwards.
| spicybright wrote:
| Is there a big difference because 3.5 and something
| digital?
|
| I know 3.5 is worse on a technically, but I've never been
| able to actually notice the difference.
| tjohns wrote:
| I think the better question is why SDI video connections
| aren't available on any consumer devices.
|
| While HDMI is nice for consumers because it carries
| audio/data, SDI cables are cheap (just a single coax
| cable!) and easy to route (T-splitters are a thing!).
|
| SDI does not support HDCP, however.
| MomoXenosaga wrote:
| On that note are there TVs with displayport?
|
| I'm using my LG TV as monitor for a PC and forced to use
| HDMI.
| dwaite wrote:
| IIRC, most panels interface via DisplayPort internally
| these days.
| beebeepka wrote:
| Gigabyte has been selling a version of LG CX48 slightly
| changed to be a monitor. It has HDMI and DP.
|
| Model name is AORUS FO48U.
| toast0 wrote:
| HDCP can run on DVI or DisplayPort too. HDMI is a smaller,
| lower pin count connector than DVI, however.
| mjevans wrote:
| HDMI's initial version is electrically and pin-compatible
| (passive adapter only) with DVI-D single link; assuming the
| DVI port supports HDCP.
|
| The parent post is correct in that the mandatory HDCP was a
| major feature (for the involved cabal of organizations).
| teh_klev wrote:
| > The parent post is correct in that the mandatory HDCP
| was a major feature
|
| This is wrong. HDCP isn't mandatory to implement HDMI,
| they are two separate technologies. I'm not defending
| HDCP or DRM encumbered content but I wish folks would get
| their facts straight.
| [deleted]
| teh_klev wrote:
| Not quite true. The "DRM" mechanism you're most likely
| referring to is HDCP which was designed separately by Intel
| to provide copy protection over multiple device types
| including DVI (the first implementation), DisplayPort and of
| course HDMI.
|
| It's not the HDMI interface that enforces copy protection
| it's the software, firmware and additional hardware on the
| devices that do this. You can use HDMI perfectly fine without
| the additional DRM crap.
| noneeeed wrote:
| I almost always err on the "never attribute to malice that
| which can be adequately explained by incompetance". Howerver,
| the "standards" bodies ability to repeatedly make a complete
| pigs ear of every single interconnect system makes me assume
| the opposite.
| amelius wrote:
| Don't forget MPEG.
| jon-wood wrote:
| Has anyone ever seen a device that actually uses Ethernet over
| HDMI? The thought of being able to plug a single network cable
| into the back of your display and then anything plugged into that
| has a wired connection is lovely, but as far as I can tell
| absolutely nothing actually supports it, despite the ever growing
| set of internet connected devices sitting underneath people's
| TVs.
| daveevad wrote:
| I went down this rabbit hole the other night and found a German
| Blu-ray receiver T+A K8[0] from 2012 that supports the HDMI
| Ethernet Channel. I have not found, however, the other piece of
| equipment that I can only suspect _may be_ be some sort of HDMI
| IP injector.
|
| [0](https://www.homecinemachoice.com/content/ta-k8-blu-ray-
| recei...)
|
| > Ethernet switch: distribution of an Ethernet uplink
| connection to BluRayplayer, streaming client, TV monitor and up
| to 3 source devices (via HEC),up to 2 more external devices via
| LAN cable (e.g. playing console
|
| from the manual
| Uehreka wrote:
| I tried to use this once in a theatre to connect a camera
| watching the stage to a greenroom backstage. It worked
| sometimes, but was super unreliable. Latency was often several
| hundred milliseconds, and sometimes the image would just
| straight up disappear. It may be that we had bad
| HDMI<->Ethernet devices, but that's the thing: It's not a
| "works or doesn't" kind of thing, it's a "varies with the
| quality of all the devices in the chain" kind of thing.
| tjohns wrote:
| Ethernet Over HDMI is used by newer AV receivers to support
| eARC (extended audio return channel). The older ARC spec would
| work with any HDMI cable, but bandwidth limitations only
| allowed compressed 5.1 surround sound. eARC uses the higher
| bandwidth from Ethernet Over HDMI, allowing uncompressed 7.1
| surround and Dolby Atomos streams.
|
| (If you're not familiar with ARC/eARC, this lets the TV send
| audio from its native inputs back to the AV receiver over an
| HDMI cable. Without ARC, you need to plug _everything_ directly
| into the AV receiver.)
| josteink wrote:
| eARC is neat in theory, but my experience with it has been
| that's too unreliable and unstable to actually use in
| practice.
|
| I even bought new cables to make sure there wouldn't be
| issues, but eARC audio regularly falls out in ways other
| sources (including regular ARC) doesn't. And when it fails
| there's literally zero tools for diagnosing it either.
|
| Maybe around the time of eARC2 we'll have something working
| as well as Bluetooth does today. (Yes, that's me being
| snarky)
| ApolIllo wrote:
| That's unfortunate. I've been hoping to simplify my HT
| setup and eARC was something I wanted to target in an
| upgrade
| simplyaccont wrote:
| actually, if i understand correctly, earc doesn't use HEC. it
| just re-purposes hec wiring for something useful
| WorldMaker wrote:
| My understanding is that Ethernet over HDMI is still used by
| consumer devices, just no longer for the original dream of
| switching wired internet given the modern ubiquity of WiFi.
| More recent standards such as ARC [Audio Relay Channel; used
| for a number of surround sound setups] and CEC [Consumer
| Electronics Control; used for passing remote/controller data
| between devices] both piggy back on the Ethernet pins, and I
| believe they entirely interfere with using the Ethernet pins as
| Ethernet (though maybe only in the available bandwidth/speed?).
| wyager wrote:
| 2021 HDMI is a disaster. I'm using a Sony flagship TV, a PC, and
| a popular Sony 7.1 receiver.
|
| I had to update my graphics card to get 4k120 444 10bit and eARC.
|
| Only eARC is totally broken - audio often doesn't work at all
| without restarting PC/TV/receiver a few times. And then once it
| "works" it will randomly cut out for 5-10 seconds at a time.
|
| HDR on windows is also totally broken. It was a nightmare to get
| something that correctly rendered full 10bit HDR video (I ended
| up having to use MPC-HC with madvr and a ton of tweaking). You
| also have to _turn off_ windows HDR support and use D3D exclusive
| mode. After updating my TV to get DRR, the audio for this setup
| stopped working.
|
| Linux also has zero HDR support. Didn't have luck getting 5.1 or
| 7.1 working either.
|
| MacOS can at least handle HDR on Apple displays - not sure if it
| works on normal displays. Haven't tried surround sound.
| MayeulC wrote:
| Not to be offensive, but -- first world problems: where did you
| find a new graphics carts, for starters?
|
| Now, a bit more on a serious tone: this is all bleeding edge.
| And combining multiple recent development together is a recipe
| for corner cases and untested combinations.
|
| That said, did you try Variable Refresh Rate with that? Bur
| reduction technologies (backlight strobing) are also
| interesting, but thankfully they require little software
| interaction (for now).
| plus wrote:
| Were you able to get 4k120Hz 444 working on Linux? What GPU do
| you have? I can only do 4k60 444 or 4k120 420 on my LG C1
| connected to my Radeon RX 6900xt.
| wyager wrote:
| I don't remember, but I had to sidegrade from a 2070Ti to a
| 3060Ti to get HDMI2.1 to get 4k120 444.
| theshrike79 wrote:
| Linus Tech Tips used a $expensive dedicated device to test a ton
| of HDMI cables. Most of them were shit:
| https://youtu.be/XFbJD6RE4EY
|
| And what was most interesting is that price and quality didn't
| always correlate at all.
| errcorrectcode wrote:
| The fundamental problem is a lack of supply chain integrity.
| Customers can buy a million cables or laptop batteries directly
| from (country that shall not be named), but they have no idea if
| they're getting fakes or not.
|
| The fix isn't "authorized" suppliers only, but requiring a
| reputable someone in the supply chain to maintain evidence of
| continually testing products advertising trademarked standards
| for compliance. If it's too much work, then boohoo, sad day for
| them, they don't get to be traded or sold in country X.
|
| In all honesty, flooding a market with cheap, substandard
| products claiming standards they don't comply with is dumping.
|
| https://en.wikipedia.org/wiki/Dumping_(pricing_policy)
| anonymousiam wrote:
| I remember when USB2 came out and similar mischief ensued. All
| the hardware manufacturers got together and pushed the standards
| body to re-brand USB 1.1 hardware as USB 2.0 (full-speed vs.
| high-speed). It allowed hardware retailers to empty their
| shelves, while consumers thought they were getting the latest
| technology.
|
| https://arstechnica.com/uncategorized/2003/10/2927-2/
| sixothree wrote:
| Same thing exists for USB3. Every time a new version is
| released, all cables and products suddenly support that
| revision. They just don't have any new features.
|
| Not to mention that I've _never_ had a cable identify what it
| is capable of. Thus USB is a shitshow of crapiness.
| michaelbuckbee wrote:
| Is there some device that can/could do this. I did a cursory
| look through Amazon and there's a lot of "signal testers", is
| that sufficient?
| driscoll42 wrote:
| There was a guy from Google going around reviewing all the
| cables testing them:
| https://arstechnica.com/gadgets/2015/11/google-engineer-
| leav... https://en.wikipedia.org/wiki/Benson_Leung
| https://usbccompliant.com/
| jmiserez wrote:
| Apparently he uses [1] a "Advanced Cable Tester v2" from
| Totalphase for his tests, starting at 15000$. Probably
| depends on what you need to test.
|
| [1] https://www.reddit.com/r/UsbCHardware/comments/ny4y6z
| /commen...
| [deleted]
| thescriptkiddie wrote:
| I recently upgraded the NVME SSD in my machine. The
| motherboard only has a single NVME compatable M.2 port, so I
| bought a USB 3.1 enclosure [0] to put the old drive in while
| I cloned it to the new drive. The enclosure has a USB type-C
| connector so I also had to use a USB 3.1 A-to-C adapter [1]
| to connect it to my motherboard's [2] USB 3.1 type-A port.
| Anyway something somewhere went wrong and it took over 5
| hours to copy 750 GB instead of the expected 10 minutes.
| Absolute shitshow.
|
| [0] https://www.newegg.com/rosewill-
| rhub-20001-enclosure/p/N82E1...
|
| [1] https://www.amazon.com/dp/B07L92KPBB
|
| [2] https://www.asus.com/us/Motherboards/Z97AUSB_31/
| anonymousiam wrote:
| I recently had nearly the opposite experience. I was
| upgrading a Linux server to a new motherboard with a NVMe
| SSD from and old one with a SATA3 SSD attached. To see how
| things would go, I imaged the old SATA3 SSD onto a
| USB3/NVMe adapter
| (https://www.amazon.com/gp/product/B07Z8Y85GL) and tried
| booting the new system from USB. It actually came up
| working, so next I figured I would need to remove the NVMe
| SSD from the USB3 adapter and install it in the motherboard
| slot, boot the system from a different USB drive, and then
| once again image the NVMe SSD from the old SATA3 drive. (I
| had read that the USB3/NVMe adapter accessed the SSD in a
| way that was incompatible with the motherboard.) So I
| installed the NVMe SSD in the new motherboard and powered
| it up just for giggles. To my great surprise, it booted
| normally and everything was fine! (Oh, and my SSD access
| speeds went from 500MB/s on the old system to 2GB/s on the
| new one.)
| MayeulC wrote:
| Why wouldn't it work? Bulk storage is bulk storage. As
| for booting from that... Linux has all the required
| drivers in the kernel, at worst (booting from radically
| different hardware) select a fallback initramfs with more
| drivers. If you did a bit-by-bit copy of your drive,
| partitions should have come out unmodified at the other
| end, including GUIDs and the EFI label on the EFI
| partition (if using EFI), or the bootloader in the MBR if
| using that.
|
| Parent is talking about speed. There are different things
| in M.2 ports (as this is the form factor): SATA and NVMe,
| PCIe AHCI[1]. There was probably a slight incompatibility
| and a fallback to some other mode there.
|
| [1] https://en.wikipedia.org/wiki/M.2#Storage_interfaces
| doubled112 wrote:
| I've definitely had problems with external storage on
| Linux machines
|
| > Why wouldn't it work? Bulk storage is bulk storage
|
| You would think so, but anything using UAS is a complete
| mess and you can't be sure it'll work. I can only assume
| devices implemented the convenient parts of the spec and
| fail randomly.
|
| Happened often enough the kernel flag for the USB quirk
| to disable UAS was stickied on the Raspberry Pi forums
| when USB boot was new.
|
| https://forums.raspberrypi.com/viewtopic.php?t=245931
| zokier wrote:
| From the review section of that enclosure:
|
| > Cons: - Included USB-C to USB-C cable is only capable of
| USB 2.0 speeds (40 MB/s as measured with crystaldiskmark)
|
| yeah, that would explain it.
| Frenchgeek wrote:
| I still had an USB 1.0 motherboard laying around not too long
| ago...
| b3lvedere wrote:
| When i had a very old Samsung tv, my Nvidia Geforce videocard
| produced a nice image to the tv and Dolby AC3 sound to my even
| older surround set via a nice hdmi to optical out converter in
| between.
|
| Now i have a not-so-old Philips tv and suddenly i can't get dolby
| ac3 sound anymore. Why? Because the GeForce communicates with the
| tv and the tv responds it only has stereo. The surround set has
| no hdmi input or output so it cannot communicate with GeForce.
|
| I have tried everything from hacking drivers to changing EDID
| with some weird devices. Nothing works. Stereo only. Very
| frustrating.
|
| I was recommended to replace my surround set or my tv. Both
| pretty expensive solutions for some weird hdmi communication
| bug/standard.
|
| So i bought a $20 usb sound device to get Dolby AC3 sound to my
| suround set. All because i replaced my old tv which couldn't
| communicate with the GeForce about its speaker setup.
| astraloverflow wrote:
| As the saying goes, a camel is a horse designed by a committee
| MomoXenosaga wrote:
| Is it really confusing? The people who need the specs of HDMI2.1
| (like gamers) will do their research.
| floatingatoll wrote:
| This is a stellar example of how catering to everyone results in
| the destruction of a brand. "HDMI 2.1" will be with us for years
| and it's essentially irrelevant now, and they aren't willing to
| admit they were wrong, so their only hope is to release an HDMI
| 2.2 that is just "all of the optional features of HDMI 2.1 are
| now required", which will cause howls of outrage and confusion.
| I'm guessing they are too captive to manufacturers to have the
| courage to do that. Oh well.
| IshKebab wrote:
| It wasn't an oversight to make the features optional. They're
| deliberately optional so device manufacturers aren't forced
| into a ridiculous all or nothing situation.
| rocqua wrote:
| AND manufacturers not wanting to be stuck with old branding
| on devices.
|
| the standard coukd have made some things optional. But they
| made everything optional.
| floatingatoll wrote:
| I think they would have been better off forcing manufacturers
| into that situation, and that the feature list has grown so
| large that it's no longer a sensible specification for
| purchasing decisions, which will erode consumer trust.
| nomel wrote:
| I see it as a problem with the abstractions being on the
| wrong layer.
| IshKebab wrote:
| It's kind of going in that direction with HDMI and
| DisplayPort over USB 3. But.. not exactly because they're
| not actually encoding video data into USB packets. It's too
| difficult to have abstractions like that when you're
| dealing with such insanely high data rates.
| Strom wrote:
| As with any tech, you can't trust marketing if you plan on
| pushing it to the limit. You need to either test it yourself, or
| in some rare cases there are reviewers who have already tested
| it. Most "reviews" for tech are extremely superficial though and
| certainly won't be testing HDMI inner workings.
|
| For HDMI 2.1, there are a bunch of monitors being sold under that
| banner that don't have the full 48 Gbps bandwidth. For example
| the Gigabyte M28U is limited to half of that at 24 Gbps. [1]
| Gigabyte certainly doesn't want you to know this. On their
| specificaion page they just list it as HDMI 2.1. [2]
|
| Similar nonsense was going on during the transition from HDMI 1.4
| to 2.0. I really wanted HDMI 2.0 output on my laptop and held off
| on a purchase until that was possible. I finally bought an ASUS
| Zephyrus GX501 laptop. It has a Nvidia GTX 1080, which does
| support HDMI 2.0 output. The marketing for this laptop also seems
| to suggest that they're utillizing this potential, with claims
| like _" You can also run a large ROG gaming monitor with NVIDIA
| G-SYNC(tm) via DisplayPort(tm) over Type-C(tm) USB or use HDMI
| 2.0 to connect 4K TVs at 60Hz."_ [3] The specification page
| mentions the HDMI 2.0 port. [4] However in reality I found out
| that this HDMI 2.0 port is limited to HDMI 1.4 bandwidth. It
| supports HDMI 2.0 features like HDR, but not the bandwidth. 4K @
| 60Hz is possible only with 4:2:0 chroma subsampling and you're
| limited to 8 bits, so no HDR.
|
| I'm not the only one who found this out either. There are plenty
| of others on the ASUS forums. [5] Hard to say whether this was
| intentional misleading by ASUS marketing, or whether engineering
| messed up, or whether the feature ended up being cut due to time
| constraints. In any case, they still haven't adjusted the old
| marketing pages for this laptop that never shipped with HDMI 2.0
| bandwidth.
|
| Reviewers don't tend to check things like this either. For
| example The Verge reviwed this laptop [6] and wrote: _" Asus has
| a nice array of ports on the Zephyrus -- four traditional USB 3.0
| ports, a Thunderbolt 3 USB Type-C port, HDMI, and a headphone
| jack."_ They're just regurgitating the marketing material.
| There's no depth to it, the claims aren't verified. So people end
| up buying the product and then get confused why it isn't working.
|
| --
|
| [1]
| https://www.rtings.com/monitor/discussions/q-D1CBeE2EiGMYgn/...
|
| [2] https://www.gigabyte.com/Monitor/M28U/sp#sp
|
| [3] https://rog.asus.com/laptops/rog-zephyrus/rog-zephyrus-
| gx501...
|
| [4] https://rog.asus.com/laptops/rog-zephyrus/rog-zephyrus-
| gx501...
|
| [5]
| https://rog.asus.com/forum/showthread.php?96916-GX501-Zephyr...
|
| [6] https://www.theverge.com/2017/8/25/16201656/asus-rog-
| zephyru...
| 0cVlTeIATBs wrote:
| I have had similar concerns with reviewers skipping USB
| compatibility on laptops. After I left comments on relevant
| reviews with a quick rundown of the problem they started
| including it.
|
| I might get at it again because I'd want my next laptop to
| drive my 4k 120Hz display over HDMI.
| alin23 wrote:
| When the new MacBook Pro came out this year, everyone was puzzled
| as to why the newly included HDMI port was only 2.0.
|
| Well it turns out they lied. It's 2.1 after all! \s
|
| Jokes aside, it's actually only 2.0 because internally they
| transmit a DisplayPort video signal and convert it to HDMI using
| an MCDP2900 chip[0], which is the same chip usually seen inside
| USB-C hubs.
|
| So the new MacBook basically got rid of the HDMI dongle by
| integrating it inside the laptop.
|
| This also breaks DDC/CI on that port and now I get a ton of
| support emails for Lunar (https://lunar.fyi) because people can't
| control their monitor brightness/volume and think that the app is
| broken.
|
| [0] https://www.kinet-ic.com/mcdp2900/
| eatYourFood wrote:
| How can I control screen brightness from my m1 max? Willing to
| pay for a solution.
| alin23 wrote:
| Lunar can do that: https://lunar.fyi
|
| It's free for manual brightness adjustments.
|
| Just make sure to use one of the Thunderbolt ports of the
| MacBook.
|
| And if it still doesn't work, check if there's any monitor
| setting that could block DDC by going through this FAQ:
| https://lunar.fyi/faq#brightness-not-changing
| MrSourz wrote:
| Neat. I've been quite fond of Monitor Control:
| https://github.com/MonitorControl/MonitorControl
| ApolIllo wrote:
| How does Lunar and Monitor Control get around the Tbolt
| -> HDMI dongle baked into the logic board problem?
| gsich wrote:
| What problem? Is DDC not available?
| pseudalopex wrote:
| They said use one of the Thunderbolt ports.
| alin23 wrote:
| There is no way to get DDC working on that port. It's
| probably locked in the chip firmware.
|
| All we can do is to provide software dimming using Gamma
| table alteration, or tell people to use the Thunderbolt
| ports instead.
| smithza wrote:
| LTT did some manual testing of HDMI cables [0] in hopes of
| answering the last question of this article, "how do consumers
| know if a cable supports v2.1 features?"
|
| Does anyone know of other tests or more comprehensive data sets?
|
| [0] https://linustechtips.com/topic/1387053-i-spent-a-
| thousand-d...
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