Choose: video on USB-C with PoE **OR** video on eth with official power supply

[ninenessa]

Hi all

We are building a school project, we have average-level Python programmer friends, but we need experienced RPi users and engineer's feedback for designing it.

Requirement:

mirror whatever's happening on laptop and stream it

Constraint:

the laptop(s) in question have only HDMI as video out

Situation:

After lots of hardware trials we finally learned HDMI female can be either output sending or input accepting but not both (why do they look identical then ).

Also, the only way to INPUT video signals in any RPi is MIPI (CSI). There's Auvidea's HDMI to CSI converter but it's too costly (don't want to burden class teacher).

So now we are looking for alternatives, searching like: "raspberry pi hdmi input", etc. Here are the alternatives we came up with (along with problems we foresee):

1. Thanks to @fruitoftheloom (& SU) for pointing out this is impossible Use converter and feed HDMI out to RPi's USB-C ... problems?
2. Use converter and feed HDMI out to RPi's Ethernet port (its possible), and use the official charger for power. But we have no experience working with eth port, and are reluctant about it's programming APIs.
3. Like #2, but we connect official charger to GPIO pins to free up USB-C for other purposes. We're not sure whether connecting the official charger to GPIO actually mitigates the need to build a regulator circuit for protecting that precious RPi .

Need feedback on:

As an experienced developer what other problems do you see in approaches 1, 2, and/or 3. What's the doablilty of those alternatives, which one would you pick? Do you have a better approach for fulfilling the Requirement. Any other feedback/pointers are welcome.

============================================================

Please note VNC is not an option.

[fruitoftheloom]

Hi all

We are building a school project, we have average-level Python programmer friends, but we need experienced RPi users and engineer's feedback for designing it.

Requirement:

mirror whatever's happening on laptop and stream it

Constraint:

the laptop(s) in question have only HDMI as video out

Situation:

After lots of hardware trials we finally learned HDMI female can be either output sending or input accepting but not both (why do they look identical then ). Also, according to Wikipedia MIPI (CSI) is the only way to INPUT video signals in any RPi. There's Auvidea's HDMI to CSI converter but it's too costly (don't want to burden class teacher).

So now we are looking for alternatives, searching like: "raspberry pi hdmi input", etc. Here are the alternatives we came up with (along with problems they create for our team):

1. Laptop's HDMI output -> converter -> USB-C input to RPi. PoE. But will the HAT create heat dissipation problems?
2. Laptop's HDMI output -> converter -> Ethernet input to RPi. Official charger for power. We have 0 experience working with eth port, reluctant about programming APIs.
3. Like #2, but we connect official charger to GPIO pins to free up USB-C for other purposes. We're not sure whether connecting the official charger to GPIO actually mitigates the need to build a regulator circuit for protecting that precious RPi .

Need feedback on:

As an experienced developer what other problems do you see in approaches 1, 2, and/or 3. What's the doablilty of those alternatives, which one would you pick? Do you have a better approach for fulfilling the Requirement. Any other feedback/pointers are welcome.

============================================================

Please note VNC is not an option.

You can not send your Laptop's HDMi output and input into the Raspberry Pi SBC via Ethernet / PoE / USB-C.....

[ninenessa]

Hi all

We are b...
...
Please note VNC is not an option.

You can not send your Laptop's HDMi output and input into the Raspberry Pi SBC via Ethernet / PoE / USB-C.....

Hi fruitoftheloom,

I made some edits for clarification.

What I said in first point was:- we use some converter from newegg to change HDMI output to make it input-able into the versatile USB-C, however this approach may create power/voltage issues, so we provide power via dedicated source i.e. PoE HAT.

We may be wrong, but in our limited understanding, according to this post it is possible to do the second approach. We just need some links or advice on how to implement it.

Also, we do understand PoE is Power over Ethernet, so there's no question of video transfer.

[fruitoftheloom]

Hi all

We are b...
...
Please note VNC is not an option.

You can not send your Laptop's HDMi output and input into the Raspberry Pi SBC via Ethernet / PoE / USB-C.....

Hi fruitoftheloom,

I made some edits for clarification.

What I said in first point was:- we use some converter from newegg to change HDMI output to make it input-able into the versatile USB-C, however this approach may create power/voltage issues, so we provide power via dedicated source i.e. PoE HAT.

We may be wrong, but in our limited understanding, according to this post it is possible to do the second approach. We just need some links or advice on how to implement it.

Also, we do understand PoE is Power over Ethernet, so there's no question of video transfer.

The Raspberry Pi 4B USB-C is directly connected to the USB2 on the SoC and like the RPi Zero it can be set in "Gadget Mode", this mode has no HDMi Video Input capability.......

[ninenessa]

You can not send your Laptop's HDMi output and input into the Raspberry Pi SBC via Ethernet / PoE / USB-C.....

Hi fruitoftheloom,

I made some edits for clarification.

The Raspberry Pi 4B USB-C is directly connected to the USB2 on the SoC and like the RPi Zero it can be set in "Gadget Mode", this mode has no HDMi Video Input capability.......

Wow, thanks for that info. So approach 1 is ruled out. Can you tell something about streaming video input that's coming through Ethernet port?

[hippy]

1. Use converter and feed HDMI out to RPi's USB-C, and provide Power over Ethernet.

If you can find a converter which captures HDMI input and delivers that to a USB-C port you can provide power direct to the Pi's GPIO power pins, do not need to use a PoE HAT.

I am not however convinced that the converters at the link you give are HDMI to USB-C for incoming HDMI capture, but are in fact USB-C to HDMI which are entirely different, unsuitable for what you want to do.

If you can find a HDMI to CSI, USB, USB-C or ethernet converter it should be usable for replicating that HDMI on the Pi's display. There may however be bandwidth issues to consider.

The easier solution would be to run some software on the laptop which captures the screen display on the laptop and sends that out over ethernet or WiFi. Much like how a Chrome browser can cast a laptop's screen to a Chromecast TV.

[fruitoftheloom]

Hi fruitoftheloom,

I made some edits for clarification.

The Raspberry Pi 4B USB-C is directly connected to the USB2 on the SoC and like the RPi Zero it can be set in "Gadget Mode", this mode has no HDMi Video Input capability.......

Wow, thanks for that info. So approach 1 is ruled out. Can you tell something about streaming video input that's coming through Ethernet port?

You keep stating you want to capture the Laptop HDMi Output, so no you can not convert that to Ethernet.

The B101 Auvidea or similar ( yes there appears to be more cost effect options ) is the answer.

An alternative is a USB HDMi Capture Card, but whether or not you could get that to work with Linux ??

https://www.ebay.co.uk/itm/372615156177

[PhatFil]

VNC is out ok, but what about other tech to stream the laptops desktop ? Is the installation and running of any server s/w within the scope of the project?

are you restricted to using the hdmi output only?

[hippy]

You keep stating you want to capture the Laptop HDMi Output, so no you can not convert that to Ethernet.

Sure one can -

https://blog.benjojo.co.uk/post/cheap-h ... -for-linux

The hard part using that method is capturing the data, rebuilding the frame buffer and displaying it.

[jj_0]

Maybe this thread offers some options? https://www.raspberrypi.org/forums/view ... 7#p1548751

[ninenessa]

You keep stating you want to capture the Laptop HDMi Output, so no you can not convert that to Ethernet.

Sure one can -

https://blog.benjojo.co.uk/post/cheap-h ... -for-linux

The hard part using that method is capturing the data, rebuilding the frame buffer and displaying it.

@hippy thanks for the link, that's super-genius level thing, how did you dig it up though?

@fruitoftheloom please consider the fact that there are 10s of HDMI-to-Ethernet adapters on Amazon, if this was impossible economics would ensure such things never got out of labs.

The term I frequently see for such adapters is *extender*, the idea is to use Cat 5e/6 cables instead of HDMI cables when interstitial length is 30-50 feet.

All I am looking for is some guide on how to stream that data that's coming in on RPi's eth port to internet

[rpdom]

@hippy thanks for the link. @fruitoftheloom please consider the fact that there are 10s of HDMI-to-Ethernet adapters on Amazon, if this was impossible economics would ensure such things never got out of labs.

The term I frequently see for such adapters is *extender*, the idea is to use Cat 5e/6 cables instead of HDMI cables when interstitial length is 30-50 feet.

All I am looking for is some guide on how to stream that data that's coming in on RPi's eth port to internet

Just because the HDMI data is being transmitted over Cat 5e/6 cables doesn't mean it is compatible with an Ethernet port in any way. I mean, I could run serial data over a length of 13A mains cable - but it wouldn't work that well if I plugged one end into a 240V mains socket (also: look up Etherkiller).

It's also like the way there are adaptors to extend the Pi camera connections by using HDMI cables - it doesn't make them work with HDMI inputs or outputs, just happens to use that type of cable.

[fruitoftheloom]

You keep stating you want to capture the Laptop HDMi Output, so no you can not convert that to Ethernet.

Sure one can -

https://blog.benjojo.co.uk/post/cheap-h ... -for-linux

The hard part using that method is capturing the data, rebuilding the frame buffer and displaying it.

@hippy thanks for the link, that's super-genius level thing, how did you dig it up though?

@fruitoftheloom please consider the fact that there are 10s of HDMI-to-Ethernet adapters on Amazon, if this was impossible economics would ensure such things never got out of labs.

The term I frequently see for such adapters is *extender*, the idea is to use Cat 5e/6 cables instead of HDMI cables when interstitial length is 30-50 feet.

All I am looking for is some guide on how to stream that data that's coming in on RPi's eth port to internet

The easiest option is to spend $10 on a USB2 HDMi Capture Device like I listed above, and see if that would work with the various software which is available for Linux....

.......everything else will cost you several $$$s and frustration and a gigantic learning curve !!

[ninenessa]

Just because the HDMI data is being transmitted over Cat 5e/6 cables doesn't mean it is compatible with an Ethernet port in any way. I mean, I could run serial data over a length of 13A mains cable - but it wouldn't work that well if I plugged one end into a 240V mains socket (also: look up Etherkiller).

It's also like the way there are adaptors to extend the Pi camera connections by using HDMI cables - it doesn't make them work with HDMI inputs or outputs, just happens to use that type of cable.

Look for any "HDMI Ethernet extender" and you'd see a pair of adaptor. One for HDMI out (laptop) and other for HDMI in (TV or monitor). Clearly, Cat 6 is a bottleneck and quality would be lost at first junction, but there's no doubt that signal through the Cat 6 cable is being converted back to good enough usable (HDMI standard) signals.

Hence, I still think it is possible to get display-able signals out of a Cat 5e/6 (I don't know about mains adaptor though ) cable.

[ninenessa]

The easiest option is to spend $10 on a USB2 HDMi Capture Device like I listed above, and see if that would work with the various software which is available for Linux....

.......everything else will cost you several $$$s and frustration and a gigantic learning curve !!

Understood. But I'll dig a little more before ordering that (or anything).

[fruitoftheloom]

Just because the HDMI data is being transmitted over Cat 5e/6 cables doesn't mean it is compatible with an Ethernet port in any way. I mean, I could run serial data over a length of 13A mains cable - but it wouldn't work that well if I plugged one end into a 240V mains socket (also: look up Etherkiller).

It's also like the way there are adaptors to extend the Pi camera connections by using HDMI cables - it doesn't make them work with HDMI inputs or outputs, just happens to use that type of cable.

Look for any "HDMI Ethernet extender" and you'd see a pair of adaptor. One for HDMI out (laptop) and other for HDMI in (TV or monitor). Clearly, Cat 6 is a bottleneck and quality would be lost at first junction, but there's no doubt that signal through the Cat 6 cable is being converted back to good enough usable (HDMI standard) signals.

Hence, I still think it is possible to get display-able signals out of a Cat 5e/6 (I don't know about mains adaptor though ) cable.

[dustnbone]

Thing is, they're not really "Ethernet" devices at all.

They're not compliant with any Ethernet standard, they merely use a cable specification that is also commonly used to carry Ethernet. It would be more accurate to call them "HDMI to Cat6", but since most people would have no idea what that meant they (mis)name them "Ethernet"

The actual data they carry across the cable has no relation to Ethernet whatsoever, therefore there isn't anything the Ethernet controller on the Pi could do with it. As far as it's concerned it's just random electrical noise.

[rpdom]

Thing is, they're not really "Ethernet" devices at all.

They're not compliant with any Ethernet standard, they merely use a cable specification that is also commonly used to carry Ethernet. It would be more accurate to call them "HDMI to Cat6", but since most people would have no idea what that meant they (mis)name them "Ethernet"

The actual data they carry across the cable has no relation to Ethernet whatsoever, therefore there isn't anything the Ethernet controller on the Pi could do with it. As far as it's concerned it's just random electrical noise.

Exactly the point I was trying to make.

[fruitoftheloom]

Thing is, they're not really "Ethernet" devices at all.

They're not compliant with any Ethernet standard, they merely use a cable specification that is also commonly used to carry Ethernet. It would be more accurate to call them "HDMI to Cat6", but since most people would have no idea what that meant they (mis)name them "Ethernet"

The actual data they carry across the cable has no relation to Ethernet whatsoever, therefore there isn't anything the Ethernet controller on the Pi could do with it. As far as it's concerned it's just random electrical noise.

Exactly the point I was trying to make.

Yes we all have unsuccessfully made this point !!!!!!

[rpdom]

Yes we all have unsuccessfully made this point !!!!!!

https://www.goodreads.com/quotes/639349 ... s-head-are

[hippy]

Thing is, they're not really "Ethernet" devices at all.

They're not compliant with any Ethernet standard, they merely use a cable specification that is also commonly used to carry Ethernet.

Exactly the point I was trying to make.

Yes we all have unsuccessfully made this point !!!!!!

Did nobody read the link I posted

Some HDMI extenders may be using ethernet cable merely as wiring, but not all. Some do use IP and the packets can be captured and used. That link shows how it was done -

https://blog.benjojo.co.uk/post/cheap-h ... -for-linux

[jj_0]

Did nobody read the link I posted

Yes, I did! Hence my silence thereafter, I've been trying to find my HDMI-to-IP adapter set ever since to try it out...

[ninenessa]

Thing is, they're not really "Ethernet" devices at all.
...
The actual data they carry across the cable has no relation to Ethernet whatsoever, therefore there isn't anything the Ethernet controller on the Pi could do with it. As far as it's concerned it's just random electrical noise.

Exactly the point I was trying to make.

Yes we all have unsuccessfully made this point !!!!!!

@dustnbone thanks for the clarification. I had it at the back of my mind, but by explicitly stating that, you've made things clearer for all of us.

Thing is, pros are not treating our questions with equal consideration, probably thinking like amateurs ....

We see your point and absolutely agree to the assertion that "The actual data they carry across the cable has no relation to Ethernet whatsoever" (@jj_0's approach is relevant to topic, but let's ignore it in this discussion).

But we doubt that the conclusion "there isn't anything the Ethernet controller on the Pi could do with it" is terminal, as in end-of-discussion-no-need-to-talk kind of thing.

Here's our train of thoughts (if you react like "this is False" at any point in the following sequence, please do not proceed and just call out our mistake, we will rebuild the train):

* in our limited experience, such (and such) adaptors are too cheap to have microprocessor/FPGA/ASIC built into them, so obviously, we are not looking at specialist encoders / decoders here.
* the stuff inside TX adaptor somehow downgrades the HDMI-out signal so the resulting bandwidth fits Cat6 cable.
* proper signal (IEEE-5688 I suppose) travels through Cat6 cable
* as there is no way to recover information lost (at TX) due to lossy signal conversion. So, the stuff inside RX adaptor must be a very simple circuit whose sole purpose is to present 8c8p as HDMI to the TV (since no algorithm/spec is implemented as hardware at this stage, i suppose RX contains only passive electrical components)
* TVs & monitors seemingly understand the downgraded signal that came through a Cat6 cable and are able to display pictures, albeit with lower quality.

When there are no special encoder/decoder components inside RX adaptor, then why can't we @ RPi make sense of signal coming in at eth port. All signals can be labelled noise, the question we're asking again and again is how to make sense of it like a TV does.

======================================

At the risk of being labelled "pointy hair boss" and stuff like that for people who doesn't understand 2 cents of IT but gives long speeches:

Forget about streaming and all other requirements mentioned in OP. Let's narrow down the problem

How to replace the RX adaptor with RPi.

We know very little electronics, but to us it seems RPi has the circuitry and the processing power (if needed) to take Cat6 video-in and spit out HDMI-out to a TV like RX adapter does.

[dustnbone]

It's really much simpler than that. The dongles aren't actively encoding and decoding the video signal in the digital sense, they merely alter the electrical characteristics to better suit the physical medium they're being transmitted across. Most of the ones that I've come across adhere to a standard known at HDBaseT.

https://en.wikipedia.org/wiki/HDBaseT

As you can read in the article, the actual data rate is over 10Gbps, and it does indeed carry the full uncompressed HDMI signal, up to certain resolution/color depth/frame rate restrictions.

One of the reason this high of a data rate can be carried on a cable that might struggle with 10Gbps ethernet is that it's mostly unidirectional, also small errors in an uncompressed video stream aren't nearly as much of a problem as the same errors in a structured data network.

So, it's still HDMI data, it never gets converted to anything else, and even if it wasn't it's over 10Gbps the Pis ethernet system cannot handle that much data, even if there was a way to directly read the data stream from it arbitrarily, which there is not.

[ninenessa]

So, it's still HDMI data, it never gets converted to anything else

Ohhh... okay. That was enlightening (like seriously, not making fun of you). I guess now the only option to look for is HDMI to USB 3.

I hope video input at USB 3 is feasible and not cursed