tty1
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Cheapest way to capture hdmi from a Windows PC?

Thu May 07, 2020 11:59 am

I know there are cheap modules like the ones discussed in this thread: viewtopic.php?f=63&t=273214
But they can only capture signals that are 1080p@25hz from what I understand. Or are the modules just outputting at 25hz but the input can be anything :?:

So if I run a normal 1080p@60hz monitor I couldn't capture the output using a splitter like this: https://www.aliexpress.com/item/32820543774.html to pipe one signal to my PC and the other signal to the capturing module. Right?

Can you think of a cheap way to do this? Maybe a device that converts 60hz to 25hz by dropping like half the frames?

I also thought about using separate outputs on the graphics card and set the screen output to duplicate, but from what I understand you can't have one monitor running at 60hz and the other one at 25hz when you do that.

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thagrol
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Re: Cheapest way to capture hdmi from a Windows PC?

Thu May 07, 2020 4:44 pm

I doubt that cable will do what you want.

From the linked page:
Please Note:
Only 1 output device should be active at any time unless both of the 2 display devices share the same size and model.
Probably just a passive cable.
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Imperf3kt
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Re: Cheapest way to capture hdmi from a Windows PC?

Thu May 07, 2020 11:36 pm

There is free software you can capture your screen with, why not use that?
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tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Fri May 08, 2020 8:26 am

@Imperf3kt Because of performance and reliability reasons.
@thagrol You're right.

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Imperf3kt
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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 11, 2020 2:44 am

You mention being okay with having to drop half the captured frames, so I assumed performance was not an issue?

Are you trying to get the video for framerate monitoring, Web streaming, video backup of gaming sessions or something? In all instances I've never noticed any performance impacts via software recording myself. The trick is to record to a different hard drive than the active drive to avoid affecting seek times.
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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 11, 2020 4:26 am

We are a video training house. We use two methods to record screen in the Windows environment:

) Camtasia. Not free but not particularly expensive.

) BlackMagic Intensity Shuttle USB 3.0. Pricey as a new box but can be picked up cheap on eBay and Craigslist. The software from BlackMagic is free. I also use it to screen record on the Pi. Here's the thread with a write up on the process.

viewtopic.php?f=38&t=188047&hilit=blackmagic+intensity

tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Wed May 13, 2020 8:31 am

The performance of the PC should not see an impact. I just don't care if the capture card rejects every second frame.

I just looked up the BlackMagic Intensity Shuttle USB 3.0 and even used it is $150. That is very expensive for a used capture card if you ask me.
And Camtasia appears to be screen recording software which is bound to have an impact on performance and reliability of the PC.


What about devices like this? It's only $12.29, but I can't tell if it could handle 60hz at 1080p. I also wonder about compression and latency.


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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 25, 2020 10:02 am

What you need is a TimVideos HDMI capture board.
https://hdmi2usb.tv/numato-opsis/

Unfortunately a bit expensive but very capable and fully open source software and hardware design. Used at various conferences to sort out their video problems.
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tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 25, 2020 12:52 pm

Well, the whole point was to find something cheap. $USD 349 seems beyond expensive imo. (Although I like the fact that it is fully open source.)

trejan
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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 25, 2020 2:57 pm

The transmitter half of a LKV373A HDMI over IP unit will accept 1080p60 but encode as 1080p30. They're cheap and do work but are somewhat quirky. There is no HDCP support, it encodes to H.264 so there is some encoding latency, you need to update the firmware and the default configuration is to use multicast. You'll need to either have a multicast capable switch or force it to send to a specific IP.

https://blog.danman.eu/new-version-of-l ... r-lkv373a/ has more information about it.

tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Mon May 25, 2020 4:08 pm

Wow, thanks for sharing, that's a very interesting device. I like how you can change the bitrate, resolution etc.

tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Tue Jun 02, 2020 8:03 am

I was able to get one of these to work on Linux with a 1080p@60hz input. Since the output is over USB 2.0 the bitrate is very low as expected and it's also rather laggy. I'd say it feels like 720p@10hz. Latency is around 500ms, I would estimate. If you look around you can find them for as cheap as $10 including shipping.

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HermannSW
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Re: Cheapest way to capture hdmi from a Windows PC?

Thu Jun 04, 2020 10:26 pm

I saw this thread sometimes and was not really interested.
Because of this thread I noticed a 1080p 30fps HDMI to USB2 for less than 20$ twitter thread.
Searching on aliexpress I found a 1080p 60fps HDMI to USB3 for 17$ incl. shipping from Spain.
Will see how it works, and whether it does what it claims:
https://twitter.com/HermannSW/status/12 ... 0593946632
video_capture.png
video_capture.png (123.62 KiB) Viewed 830 times

P.S:
Back in February I found a 9" 1024x600 HDMI display plus driver card and all that is needed for 26$ in total (free shipping).
I ordered it, and received it in March, and it works perfectly:
viewtopic.php?t=254059#p1613145
So unbelievable cheap products can do what they claim ...
https://stamm-wilbrandt.de/en/Raspberry_camera.html
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/raspiraw
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://stamm-wilbrandt.de/working_with_FPGAs

tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Fri Jun 05, 2020 8:32 am

Thank you, that one sounds really interesting! I ordered one as well, let's see if it can do what it claims.

(Another way to get your hands on a cheap screen is to buy an old laptop screen or salvage an old/broken laptop. Those can be found for very cheap or even for free if you're lucky. The tricky part about laptop screens is that you have a find a compatible controller. Something like this for example. But the advantage is that you get a relatively big screen, any ports you want (HDMI, DVI, VGA, ...) and higher resolutions like 1080p. Also, laptop screens are incredibly thin.)

tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Tue Jun 09, 2020 1:45 pm

Here's another interesting one for $15: https://www.aliexpress.com/item/4001061528924.html
It's USB 3.0, allows capturing up to 4k and it has an HDMI OUTPUT (not just an HDMI input). Unfortunately it only supports up to 30hz according to the description. But I wouldn't be surprised if it could actually handle 60hz while running at 1080p.
Even if it doesn't, for $15 it still seems like a good value, especially considering the $10 that you might save because you wouldn't need an HDMI splitter like this.

Edit:
@HermannSW I also found another offer for the one that you mentioned for about $10: https://www.aliexpress.com/item/4001051226399.html

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Re: Cheapest way to capture hdmi from a Windows PC?

Tue Jun 09, 2020 3:00 pm

tty1 wrote:
Thu May 07, 2020 11:59 am
I know there are cheap modules like the ones discussed in this thread: viewtopic.php?f=63&t=273214
But they can only capture signals that are 1080p@25hz from what I understand. Or are the modules just outputting at 25hz but the input can be anything :?:

So if I run a normal 1080p@60hz monitor I couldn't capture the output using a splitter like this: https://www.aliexpress.com/item/32820543774.html to pipe one signal to my PC and the other signal to the capturing module. Right?

Can you think of a cheap way to do this? Maybe a device that converts 60hz to 25hz by dropping like half the frames?

I also thought about using separate outputs on the graphics card and set the screen output to duplicate, but from what I understand you can't have one monitor running at 60hz and the other one at 25hz when you do that.
To correct the original post, the TC358743 based chips can capture up to 1080p50 on a standard Pi. The 1080p25 is a relic from Auvidea's documentation when using the firmware drivers instead of the Linux kernel ones.

Dropping the framerate means that some device has to have enough RAM to store an entire frame and read it out at a slower speed. Very few devices work that way. The TC358743 has something like a 512 pixel FIFO, so the two data rates have to be at least approximately matching.

Set the EDID appropriately on your capture device and your source will generate video in a matching format. Do you need 1080p60? Remember that the H264 encoder on the Pi needs overclocking to achieve that, so what is your consumer?

4k30 will be because to bump up to 4k60 requires a load more options as it switches up to HDMI 2.0. HDMI 1.4 maxes out at 4k24 (possibly 30) and 8bit colour, whilst HDMI 2.0 goes up to 4k60 and up to 12 bit colour.
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tty1
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Re: Cheapest way to capture hdmi from a Windows PC?

Wed Jun 10, 2020 2:14 pm

Thanks for clarifying. And yes do do need a 1080p@60hz connection between the Windows PC and the display. So even if I ran the capture card at 50hz that wouldn't quite be enough to capture the signal.

The basic idea is:

Code: Select all

                                                      ---[Monitor running at 1080p@60]
[Windows PC outputting 1080p@60]---[HDMI splitter]---|
                                                      ---[Capturing device]---[Raspberry Pi 4]
And then on the Pi I want to write a couple of scripts that analyze some the frames with (hopefully) little delay. For example to make an ambilight that works while gaming at 60fps. And I'm sure I could come up with lots of other cool things to do with it.

Also, would I need additional cooling when overclocking the H264 encoder?

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Re: Cheapest way to capture hdmi from a Windows PC?

Wed Jun 10, 2020 2:20 pm

tty1 wrote:
Wed Jun 10, 2020 2:14 pm
Thanks for clarifying. And yes do do need a 1080p@60hz connection between the Windows PC and the display. So even if I ran the capture card at 50hz that wouldn't quite be enough to capture the signal.

The basic idea is:

Code: Select all

                                                      ---[Monitor running at 1080p@60]
[Windows PC outputting 1080p@60]---[HDMI splitter]---|
                                                      ---[Capturing device]---[Raspberry Pi 4]
And then on the Pi I want to write a couple of scripts that analyze some the frames with (hopefully) little delay. For example to make an ambilight that works while gaming at 60fps. And I'm sure I could come up with lots of other cool things to do with it.
If you want 1080p60 through the TC358743, then you have to use a Compute Module, and either Auvidea B102 or it looks like some of the Chinese boards do break out all 4 lanes if they have the 22pin connector.
Yes, once in memory it is quite easy to only process every other frame if you haven't got enough processing power to do every frame.
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