Multiple HDMI Displays on a "Bus"  - Page 1
Forum section: electronics / projects

author: luky315
author_rank: Regular Contributor
timestamp: July 19, 2024, 06:45:35 pm
content: I have multiple (4 to 16) Full-HD displays with HDMI input and I need to have the same picture on every display. They are also far apart and there are some special requirements regarding the power supply and the cables, so I need a custom solution. I have experience with high speed cable drivers over long distances and in harsh environments, so this shouldn't be the main problem. But I'm a bit confused regarding the required signals: If i define/use the first one as sort of master by connecting the I2C, CEC and Hot Plug Detect signals only to this display, is it then possible to "copy" the 4 pairs of TDMS signals via CML Fanout buffers (in my case probably devides with equalizing) to the other displays on the bus? Would the "slave" displays then simply show the duplicated signal when they get power? Or is there some sort of bidirectional communication required? HDCP is not required, so this shouldn't be a problem.

author: themadhippy
author_rank: Super Contributor
timestamp: July 19, 2024, 06:52:01 pm
content: Any reason for not using an of the shelf HDMI splitter

author: luky315
author_rank: Regular Contributor
timestamp: July 19, 2024, 06:57:18 pm
content: Yes, a lot of reasons, one of them being that I cannot use HDMI cables and we don't have the space to hide the quite big of the shelf ones including the necessary converters.

author: tooki
author_rank: Super Contributor
timestamp: July 19, 2024, 07:39:45 pm
content: A question to think about (not rhetorical; I don’t know the answer) is whether HDMI can actually function without HDCP. I know that HDCP support is mandatory for HDMI devices, but I don’t know whetherusingHDCP is mandatory or not. If so, would an HDMI receiver even work if fed an unencrypted feed?

author: coromonadalix
author_rank: Super Contributor
timestamp: July 19, 2024, 07:54:25 pm
content: fiber optics hdmi?

author: luky315
author_rank: Regular Contributor
timestamp: July 19, 2024, 08:38:13 pm
content: Using HDCP is not mandatory - the source can request / enforce it.Fiber optics is nice for lon distances and harsh environments, but also only point to point - the question is still if it is enough to feed the 4 TDMS Lanes into the other displays to get a picture

author: macboy
author_rank: Super Contributor
timestamp: July 21, 2024, 11:32:43 am
content: Maybe HDBaseT is something you need to look at. You can get splitter/distribution systems using this.HDMI splitters generally will do one of two things: One option is to determine the lowest common denominator (lowest supported resolution) for all connected displays, and present that to the source over EDID. The other is to have a master port whose EDID is copied and presented to the source. In either case, all displays get the same video. Uncommonly, some splitters are also scalers, and can convert the video to match the capability of each display. Obviously this is much more complicated and therefore more expensive.

author: wasedadoc
author_rank: Super Contributor
timestamp: July 21, 2024, 02:45:43 pm
content: What is the original source? Is it feasible to distribute over ethernet to a number of Raspberry Pis which each feed one or two displays?

author: luky315
author_rank: Regular Contributor
timestamp: July 21, 2024, 06:32:57 pm
content: Feasible maybee - but if I can avoid a raspi I'm happy

author: darkspr1te
author_rank: Frequent Contributor
timestamp: July 22, 2024, 07:13:35 am
content: You might want to look at HDMI over ip ,There are usually two ways these work, Normal units have a HDMI to IP tx unit then a IP to HDMI rx unit but more industrial ones can have one main and many child units for example the OREI 1 to 6 HDMI extender.Some newer models work with smart tv's and can view the HDMI signal via a website or app so you would have only a Main unit to encode and all the tv's get the picture via LAN or wifi.A company called brightlink provides 65 channels in and up to 200 units out via lan and wifi, it can be small or large setup (eg master video server+billing platform) and also carry IR signals for channel switching & setup/maintenance as well as logging channels watched etc and also TV control (eg auto power on, auto channel select etc)I have installed a brightlink at a hotel and must admit it was easy , the model they supplied had GB lan passthrough so only one cable required for each room and it was all auto setup via the app on android , it detected the all the units and TV types and took less than a afternoon for 100tv's, it was as plug and play as you get.darkspr1te