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> HDMI resolution, Resolution of external display via HDMI question
Radovan Garabík
post Jan 23 2019, 07:07 AM
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I am a (semiproud) new owner of the Gemini, and I am considering buying the Planet's HDMI adapter. However, I have a crucial question - what resolutions does the HDMI output support? Basically from the hardware point of view; by reading various discussion I am starting to suspect that this is fixed at the LCD resolution of 2160×1080. Since there are monitors (and especially projectors) that support only certain resolutions (or up to a certain resolution), is there a way of changing it? Has anyone here successfully connected Gemini HDMI in lower than native resolution mode? I am mostly interested in Android and Linux, but I am not sure if the current Debian supports HDMI at all.

Failing that, I would go rather for {chrome,mira}cast instead of the cable, but the same question remains, I am not sure if it is possible to change the resolution here.
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Adam Boardman
post Jan 26 2019, 01:38 AM
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I've not tried the cable much as we've not enabled it in Debian just yet so I cannot help with the output resolution options, actually I don't think I have any non 1080P HDMI screens anyway. I suspect/hope it just scales to fit. It is an independent output at the hardware level as can be seen in the presentation software. One rumour* that I have heard is that they might be trying to get the Cosmo to work with generic USB-C HDMI cables, and that this work might then also be back portable to the Gemini. So depending on how urgently you want external displays support it might be worth waiting the 6-12 months or whatever it takes for the Cosmo release to see if that ended up being possible. Then you could just get a generic cable that would work across many devices.

* - someone in Telegram chat room asked Planet and reported back
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Daniel W
post Jan 28 2019, 02:40 PM
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As far as I know, the resolution from the Gemini via its HDMI adapter is "(o) auto" only, which seems to be its native 2160x1080.

I have, thus far, tried the HDMI adapter with two TV sets. One of them is a regular 1920x1080 model. It says it's receiving 1080p @ 60Hz, and since it scales the image a bit, leaving small black bars top and bottom, I'd say it's 2160x1080p @ 60Hz. If I connect the Gemini to it via a Miracast receiver (an old Netgear P2TV 3000), it still says 2160x1080p @ 60Hz. As the actual HDMI signal, in this case, is generated by the Miracast receiver, it may depend of the model used, but I don't think I can change the resolution on mine anyway.

The other TV has a somewhat odd LCD panel (32" 1366x768 with its RGB stripes turned 90 degrees). It, too, says 1080p (but doesn't specify a frame rate) and, by default, scales the image to fit the width, with bars top and bottom. I haven't tried that one with the Miracast device, but I'd expect the same result.

One thing to note, which I've written about here is that both connection methods has a bit of lag and, unfortunately, doesn't delay audio and video equally. In my experiments, HDMI gives me 100-120ms video lag and 150ms audio lag, while Miracast gives me about 380-400ms video lag and 300ms audio lag. Depending on whether you need audio in sync with the video or not, that might be a bigger issue (it is for me, anyway) than the resolution, as most (though pehaps not all) modern display devices will likely be able to handle the 1080p signal.
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Radovan Garabík
post Feb 3 2019, 11:58 PM
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QUOTE(Daniel W @ Jan 28 2019, 11:40 PM) *
As far as I know, the resolution from the Gemini via its HDMI adapter is "(o) auto" only, which seems to be its native 2160x1080.


Thanks, that's what I was suspecting (unfortunately). I would not mind some downscaling (given native resolution) or minor black bars, but getting no picture at all is bad (my TV is 1650x1050 and it does not support FullHD input I am in no hurry to replace it, and projectors more often than not do not support FullHD).

QUOTE
One thing to note, which I've written about here is that both connection methods has a bit of lag and, unfortunately, doesn't delay audio and video equally. In my experiments, HDMI gives me 100-120ms video lag and 150ms audio lag, while Miracast gives me about 380-400ms video lag and 300ms audio lag. Depending on whether you need audio in sync with the video or not, that might be a bigger issue (it is for me, anyway) than the resolution, as most (though pehaps not all) modern display devices will likely be able to handle the 1080p signal.


That is unfortunate. I guess I could fix the lag with pulseaudio on Linux, but Android is out of question. I assume you are talking about audio via HDMI, not the audio jack or built-in speakers.
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Daniel W
post Feb 5 2019, 03:12 PM
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QUOTE(Radovan Garabík @ Feb 4 2019, 08:58 AM) *
I assume you are talking about audio via HDMI, not the audio jack or built-in speakers.
Correct.
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spook
post Mar 6 2019, 08:58 PM
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I've has bad luck getting the PC adaptor to work with different screen. I eventually went with a DisplayLink adapter and it works with any screen I plug it into (even with an HDMI adapter attached). That doesn't really answer your question, but it might be an avenue worth exploring.
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