Talk:HDMI

Accessibility

This article needs to address accessibility of the HDMI standards. It seems like audio description for the blind can be included on one of the audio channels. The HDMI standard does not include communication access though for people with hearing loss or non-native speakers of the primary language (no streams for closed captioning data whether for deaf and hard of hearing or anime/foreign language) so in order to use HDMI with captions, the originating equipment must decode the data and pass the generated pictures of text to the end equipment. This limits the accessibility for persons with hearing loss, especially those with visual impairments. Televisions in the United States are required to have closed caption decoder chips and the visibility can be changed to the user's liking for over the air or Video/Audio inputs but this does not work for HDMI inputs since they do not pass the caption data through. This limits the ease with which physically disabled persons can use captions since they cannot just turn their television caption decoder on once and be done, they must turn on captions on each piece of sending equipment when using HDMI. This makes it harder for children and the aged to gain ease of use for captions. This also increases costs for everyone as with HDMI all of the sending and receiving units must have decoder chips (receiving units/televisions for over the air caption data.) — Preceding unsigned comment added by 2602:30A:C049:EA80:4885:EA70:59A9:82AB (talk) 18:30, 9 June 2014 (UTC)

As far as I know it, this isn't part of HDMI. HDMI moves the signal from source to destination. Audio signals will be supplied by the source, selected from those available. For example, a DVD player will select from the available audio tracks and send one out. I believe CC is also selected and decoded inside a DVD player, and the resultant video sent out. CC decoders in television sets will decode ATSC (or NTSC) closed-caption signals. An external tuner, connected through HDMI, will also do that. Gah4 (talk) 22:09, 25 February 2021 (UTC)

«DisplayPort has a royalty rate of US$0.20 per unit (from patents licensed by MPEG LA),»

It's only a claim. Whether it's correct or patent trolling is up for debate and court rulings. DisplayPort is meant to be royalty-free. See https://en.wikipedia.org/wiki/DisplayPort#Cost

How could this be reworded to be more accurate? (if that's a correct understanding)

--Tuxayo (talk) 16:41, 4 August 2020 (UTC)

Does HDMI 2.1 indeed support for 4k 144hz?

The article claims, without providing any source or references, that HDMI 2.1 supports 4k 144hz. The problem is that official hdmi.org website has no such information, it says that HDMI 2.1 supports maximum 120hz at 4k resolution. After a lot of googling and reading tech websites, I think that everyone just *assumed* that HDMI 2.1 will support 4k@144hz solely because it has enough bandwidth for that. But developers of hdmi 2.1 specifications never confirmed that. And since the only HDMI 2.1 monitors currently on the market are TVs with screen refresh rate limited to 120hz, there is no way to verify if HDMI 2.1 can handle anything above it or not. It's also unclear if those few 4k@144hz PC monitors to be released next year (Eve, Acer, ViewSonic, Philips) indeed support uncompressed output through HDMI 2.1, or it will be limited to 4k@120hz and 144hz will be possible only through DSC? Again, after reading all the news reports I think that tech websites *assumed* that these monitors will support uncompressed 4k@144hz through HDMI 2.1 just because it has enough bandwidth for that. But these assumptions were never confirmed by manufacturers of the monitors. Can anybody please further clarify this? 46.172.22.218 (talk) 20:45, 30 November 2020 (UTC)

There is some confusion due to the word "support", which has a special meaning in the HDMI Specification compared to normal casual usage. Running at 4K 144 Hz is fully within the guidelines defined by the HDMI Specification. Nothing about 4K 144 Hz is out of spec and there is no restriction on running at 4K 144 Hz. It is therefore possible to run at 4K 144 Hz using the HDMI interface. If that's what you mean by "support" then yes, HDMI 2.1 supports 4K 144 Hz. HDMI allows any arbitrary video format, as long as it is within the restrictions of the HDMI Specification, such as the maximum aggregate bit rate of 48 Gbit/s. This is established in section 6 of the HDMI specification, the very first sentence of the video section of the HDMI Specification. HDMI does not need some kind of special "support" for every particular format in order to run it. As long as it is within the bandwidth limit, it is allowed, so it is just a matter of math. 4K 144 Hz is therefore possible over HDMI.

There is a list of "Supported Formats" in the HDMI Specification. These are common formats that the HDMI Specification explicitly defines all the timing parameters for (via the CTA-861 standard). The purpose of these formats is explained in Section 6; they are to ensure interoperability for common formats, so that if two device supports 1080p 60 Hz for example, they will support the exact same timings and therefore are guaranteed to work with each other without any unexpected out-of-range errors or anything like that. In the HDMI Specification, "Supported Formats" refer to formats with explicitly defined timings. In no way is the HDMI Specification restricted to only transmitting "Supported Formats"; as explained in Section 6, any arbitrary format is allowed. The Supported Formats list is only to aide interoperability between products with these common TV formats. People who don't understand the Specification will often point to this table saying "look, XYZ format isn't in the supported formats table, therefore HDMI doesn't support it!" without understanding that "support" has a non-normal meaning in the HDMI Specification. So it is technically true that HDMI does not "support" these formats, but as mentioned, the HDMI Specification has a special meaning for the term "supporting" a format, which does not mean what people usually mean.

If you examine the list you will also note that 1080p 144 Hz is also not a Supported Format. 2560 × 1440 is also not a Supported Format, neither is 1366 × 768. Yet clearly there are many monitors on the market that run at these formats over HDMI. Likewise, is 4K 144 Hz a Supported Format? No. But does HDMI 2.1 support running at 4K 144 Hz? Yes. Don't be confused by tables of "Supported Formats"; HDMI is not restricted to only transmitting these formats. Any format within the bandwidth limit is allowed. This is stated by the HDMI Specification in Section 6 and is the reason that 1080p 144 Hz monitors and 1440p monitors with HDMI exist.

Please also note that this only deals with what is permitted by the HDMI Specification. It is possible that products may only support up to 4K 120 Hz. This is because products may have any arbitrary limitations. For example, some 1080p 144 Hz monitors are limited to 60 Hz over HDMI, some are limited to 120 Hz over HDMI, some support 144 Hz over HDMI. So it is entirely possible that upcoming monitors might only support up to 4K 120 Hz over HDMI. This does not prove or disprove anything about what the HDMI Specification allows, only what that product is capable of, because product capabilities are arbitrary. The HDMI Specifications only describes what products are allowed to do, and how to do those things. So you cannot determine what the HDMI Specification supports or does not support by inferring from what products on the market are limited to. GlenwingKyros (talk) 21:37, 30 November 2020 (UTC)

DSC (all B formats) is NOT lossless!

I wanna add that info in the article, the non-RS is a Youtube video. This was an important info that was not here. I think it is important that in by itself DSC is lossy, even though it should use lossless YCgCo-R! https://www.avsforum.com/threads/hdmi-2-1-chipset-bug-in-dennon-marantz-and-yamaha-receivers.3171161/post-60213663 109.252.90.66 (talk) 11:56, 25 February 2021 (UTC)

“DSC (all B formats) is NOT lossless!” The article never claims that it is. It sounds like you're having a reaction to something that isn't there.

“I wanna add that info in the article, the non-RS is a Youtube video.” I can't understand what you're saying. What is “the non-RS”? What YouTube video? You appear to have linked a forum thread. But DSC being a lossy form of compression isn't some kind of secret, it's on the VESA FAQ page.

“I think it is important that in by itself DSC is lossy, even though it should use lossless YCgCo-R!” Such technical details don't really belong here, this page is about HDMI, not for informing people about DSC. If people want to know more about DSC, they can click the Wikilink, that's what it's there for. GlenwingKyros (talk) 18:08, 25 February 2021 (UTC)

HDMI gets bits from a source to destination. There is no loss in that. If a lossy compression was used, such as for DVD, that happens when creating the DVD. The DVD player creates a digital signal and send it into the HDMI cable. The same signal arrives at the other end and is (usually) displayed. Gah4 (talk) 22:14, 25 February 2021 (UTC)

He's talking about Display Stream Compression (DSC), which is an optional lossy compression (though very low compression ratio) used during transmission over HDMI. GlenwingKyros (talk) 22:53, 25 February 2021 (UTC)

Strange, I though it is obvious that on the forum the video that is used is an embedded Youtube video. "bits from a source to destination. There is no loss in that", common mistake. Almost all video on the planet (all on DVDs, on Blu-rays, on Youtube) is 4:2:0. It will be only lossless if you will actually send the 4:2:0 as in the stream (passthrough) to the 4:2:0 HDMI link. After quantisation, when float is converted to fixed RGB on even YCbCr 4:4:4 8 bit value (or 10, or 12) it is not the same anymore. Just saying. (Though I am only sure about RGB.) 109.252.90.66 (talk) 21:21, 26 February 2021 (UTC)

I think I must have scrolled when the page loaded, I didn't notice it linked to a specific post. GlenwingKyros (talk) 21:40, 26 February 2021 (UTC)

DVI-D to HDMI adapters do not appear to be single-link only

While the article states that such adapters are single-link only, page 139 of the linked PDF lists a "Type B to DVI Adapter Cable," which appears to have all the wiring assignments required for dual-link. This is preceded by "Type A-to-DVI-D" on page 138, which is indeed single-link. Did someone misread the document, or am I confused? Thanks. — Preceding unsigned comment added by 73.88.59.121 (talk) 21:46, 18 March 2021 (UTC)

A Type B to DVI adapter could in fact be dual link - theoretically. I don't think they exist. --Zac67 (talk) 21:51, 18 March 2021 (UTC)

I suppose that info should be added to article? — Preceding unsigned comment added by 73.88.59.121 (talk) 22:07, 18 March 2021 (UTC)

The mechanical specifications for an HDMI Type B connector was defined in the specification for later use, but not permitted for use in products. The intent was to allow compatibility with dual-link DVI as you describe, but ultimately they decided not to use dual-link operation in HDMI, so the Type-B design was never used and remains to this day a theoretical concept only. GlenwingKyros (talk) 22:21, 18 March 2021 (UTC)

I think we should mention that in the article, I can't be the only person disbelieving of single-link only, going to the linked PDF, and then being confused. — Preceding unsigned comment added by 73.88.59.121 (talk) 22:29, 20 March 2021 (UTC)

Change all 48 Gbit/s to 48.11 Gbit/s

People are really confused online, see https://images.idgesg.net/images/article/2017/12/formatdataratetable-100743742-orig.jpg Also, 40.1 instead of 40 and 32.08 instead of 32 (LG CX and PS5). 109.252.90.119 (talk) 22:09, 4 November 2021 (UTC)

That table shows bit rates required for various video formats. Not the bit rate of the HDMI interface. GlenwingKyros (talk) 22:29, 4 November 2021 (UTC)

Is not that only correct for DSC 1.2 formats? What is the math there? 109.252.90.119 (talk) 22:37, 4 November 2021 (UTC)

I don't understand your question. What are you referring to? Is what only correct for DSC? GlenwingKyros (talk) 22:43, 4 November 2021 (UTC)

Only for DSC 1.2 the data rate and uncompressed data rate are different, is it not? Not counting 16b/18b, sice that is 42.6666.../16*18 = 48.000 42.666... is mentioned in the article, is that correct? 109.252.90.119 (talk) 02:30, 5 November 2021 (UTC)

If DSC compression is not used, the uncompressed data rate is the data rate. None of the bit rates listed on the table you linked include compression in the calculation, and neither do any of the tables in this article, so I don't know how it is related to anything. Can you clarify which part of the article you think needs to be changed, and why? GlenwingKyros (talk) 02:36, 5 November 2021 (UTC)

I think all mention of 48 Gbit/s should be 48.11 Gbit/s. 109.252.90.119 (talk) 14:39, 5 November 2021 (UTC)

The bit rate of HDMI 2.1 is 48.000 Gbit/s, not 48.11 Gbit/s. GlenwingKyros (talk) 18:05, 5 November 2021 (UTC)

Then what is 48.11 Gbit/s? Valery Zapolodov (talk) 07:51, 6 November 2021 (UTC)

The bit rate of the video format on the table? GlenwingKyros (talk) 08:15, 6 November 2021 (UTC)

After 2.1?

So what is being developed as v2.2 or v3.0 (or whatever number they choose to call it)? 2.1 is effectively being put in everything now, so is largely the release standard in products, but surely R+D work is being done on the next standard... yet nothing in the article about what is needs to be able to do, or what's being planned/aimed for (eg. 16K, higher frequency rates, etc.)? (Yes, I know some things remain business secrets, but a lot of this is likely to be obvious expected capabilities that can be mentioned.) Jimthing (talk) 15:54, 13 December 2021 (UTC)

Audio

Should not the audio be simply… limited to the tuner’s decoder? HDMI is as passive in data signals as any other wire. MacOS doesn’t support 5.1 in 2 DTS note does VLC which outputs the raw 2ch stream but my tuner picks it up just fine and decodes it before sending 5.1 to speakers. Lostinlodos (talk) 11:29, 23 December 2021 (UTC)