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Cheap HDMI capture for Linux

blog.benjojo.co.uk

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Re: Cheap HDMI capture for Linux

#71

Post by brigade »

pjc50 wrote: post #69
rsync wrote: post #50

"These units are not perfect for quality, however they are not bad at all, Here is a screenshot taken on my laptop..." I am confused by this ... HDMI is a digital interconnect and deals in digital I/O ... in my mind, if you succeed in capturing that HDMI, the resulting stream should be identical ... why would there be a quality (or any other) difference ?

You nearly always want the capture device to compress because it's otherwise very hard to handle. 1080p/60/8 HDMI is 4.46Gbps; just about fits in a USB3 or PCIe3 data link, but exceeds most SSDs' write bandwidths.

? Most all half-decent SSDs can saturate a 6Gbps SATA link either direction; that's why they're moving to PCIe.

Also, 1920x1080x60x24 is just under 3Gbps; where are you getting 4.46?

And even if you wanted to record compressed video, you'd almost certainly get better quality feeding it through other HW encoders if you didn't want to spend CPU time on it.

Re: Cheap HDMI capture for Linux

#73

Post by icebraining »

phkahler wrote: post #54
benjojo12 wrote: post #14

Earlier quoted context omitted.

This device happily decodes HDCP. I figured the manufacturer does not care

>> This device happily decodes HDCP. If used as intended will it allow an HDCP source to show on a non-HDCP display? Because stupid AppleTV won't allow "protected" content to display on mt main TV because it doesn't support HDCP, and if you buy something on iTunes you don't find out until you've already purchased it. DRM is driving me away from services like that and I'd rather just stop using them than buy another T…

You're probably better off buying an HDMI-in/out device like [1]. It's a "splitter", but you can just plug the HDMI-in in one side and one HDMI-out in the other, and since it doesn't enforce HDCP on the output, it works as a stripper.

[1] https://www.amazon.com/ViewHD-Powered-Splitter-1080P-Model/d...

Re: Cheap HDMI capture for Linux

#74

Post by Hytosys »

nacs wrote: post #41
Hytosys wrote: post #25

Earlier quoted context omitted.

I coded the Blackmagic support for OBS Studio. It was only slightly nightmarish. https://github.com/jp9000/obs-studio/tree/master/plugins/dec...

Thanks for creating that. I use OBS so this sounds perfect. Could you recommend a Blackmagic product supported by your plugin that can capture from HDMI (cheaper the better, I plan to use it for hobbist-level capture of desktop/games)?

Awesome!

I used the Intensity Shuttle for USB 3.0 on a Macbook (OS X) to develop the plugin. It costs $190 and works pretty well, but can't capture 1080p @ 60fps (only 720p/1080i). I only got it because I couldn't install a PCI-e card on my laptop ;)

If you need 1080p @ 60fps, the Intensity Pro 4K is also $190 and is a PCI-e card. Otherwise, the Mini Recorder should work just fine.

Re: Cheap HDMI capture for Linux

#75

Post by [deleted] »

riskable wrote: post #51
rsync wrote: post #50

"These units are not perfect for quality, however they are not bad at all, Here is a screenshot taken on my laptop..." I am confused by this ... HDMI is a digital interconnect and deals in digital I/O ... in my mind, if you succeed in capturing that HDMI, the resulting stream should be identical ... why would there be a quality (or any other) difference ?

Because they compress the video before sending it over IP. Nothing fancy, just M-JPEG which is basically the same thing as taking a screenshot of the video every nth of a second and saving it as a high-quality JPEG (probably around 95% quality rating). The screenshot in the video suggests 1000fps but that figure is highly dubious. It is much more likely to be 30 or 60fps on a cheap HDMI->IP converter like this.

[deleted]

Re: Cheap HDMI capture for Linux

#76

Post by pests »

patja wrote: post #48

Can it capture a 5.1 AC3 audio stream along with the video?

I don't know the details, but this is from the article:

"[...] by default it will output matroska, aka mkv with both video and audio so that it can be easily interfaced with (no compression happens in this stage, just containerisation).

Re: Cheap HDMI capture for Linux

#78

Post by beagle3 »

This is awesome. I was just thinking about something that could be even more awesome: if someone produced an HDMI to MIPI CSI adapter - that would allow e.g. a RasPI to have an "HDMI in" port.
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