MrMC

I have a feeling that your optimal and my optimal are not the same, so I will gracefully bow out of this conversation.

amet wrote: 09 Oct 2018, 12:25 I have a feeling that your optimal and my optimal are not the same, so I will gracefully bow out of this conversation.

Among other things, my optimal is the combination is settings where the pixel colour values that the media player sends to the display are as close as possible to the pixel colour values actually encoded in the video file being played.

Are you saying you prefer the pixel colour values to be objectively wrong?

Recommending settings depends on many factors of which we have zero control over.

So we setup the defaults to be 'sane'.

davilla wrote: 09 Oct 2018, 13:09 Recommending settings depends on many factors of which we have zero control over.

This is like pulling teeth!

How about telling us a combination of MRMC settings and Shield TV settings which gets as close as possible to objectively accurate pixel-colour values?

It doesn't matter whether any given setting is under MRMC's control or not - if you just tell us what it is, we can set it manually. All we need is the information!

If you want, come at it from another angle: I assume you have actually done some tests on the Nvidia Shield to verify that approximately correct pixel values are achievable at all. What settings did you use when conducting that test?

Shasarak wrote: 09 Oct 2018, 13:26
How about telling us a combination of MRMC settings and Shield TV settings which gets as close as possible to objectively accurate pixel-colour values?

If you're playing something that's rec.709 you should manually set the output of the Shield to YCbCr 4:4:4 8bit Rec 709 and let MrMC automatically switch the resolution. If you're playing something that's rec.2020 you should manually set the Shield output to YCbCr 4:2:0 10bit Rec 2020.

timstephens24 wrote: 09 Oct 2018, 20:11

Shasarak wrote: 09 Oct 2018, 13:26
How about telling us a combination of MRMC settings and Shield TV settings which gets as close as possible to objectively accurate pixel-colour values?

If you're playing something that's rec.709 you should manually set the output of the Shield to YCbCr 4:4:4 8bit Rec 709 and let MrMC automatically switch the resolution. If you're playing something that's rec.2020 you should manually set the Shield output to YCbCr 4:2:0 10bit Rec 2020.

Good to know. As I recall, SPMC recommends RGB rather than YUV444, so clearly one shouldn't assume recommended settings for other Kodi forks apply here - hence why the question was an important one. (Also because, if one is not familiar with the code, it's not obvious whether the video remains in YUV space right through the pipeline, or is converted to RGB at an intermediate stage - if that were happening then converting back to YUV again would be unhelpful.)

Also interesting that you aren't recommending 4:2:0 8-bit in cases where the resolution and frame-rate supports it. (In my experience so far, the Shield's chroma upsampling hasn't been very good).

4:2:0 10-bit YUV for rec.2020 poses a problem: it limits you to 50Hz, 59.94Hz or 60Hz refresh-rate, which will give 3:2 judder on 24fps film material. How much of an image quality hit do you get switching to 12-bit 4:2:2 rec.2020 instead?

Shasarak wrote: 09 Oct 2018, 21:22 Good to know. As I recall, SPMC recommends RGB rather than YUV444, so clearly one shouldn't assume recommended settings for other Kodi forks apply here - hence why the question was an important one. (Also because, if one is not familiar with the code, it's not obvious whether the video remains in YUV space right through the pipeline, or is converted to RGB at an intermediate stage - if that were happening then converting back to YUV again would be unhelpful.)

Generally most videos are done at YCbCr 4:2:0 so if you want you can do that instead of YCbCr 4:4:4 for rec.709 videos. You can also do RGB, there shouldn't be any issues doing that at all. It's just personal preference (or should be unless the Shield started messing something else up in the conversions) at that point.

Shasarak wrote: 09 Oct 2018, 21:22 Also interesting that you aren't recommending 4:2:0 8-bit in cases where the resolution and frame-rate supports it. (In my experience so far, the Shield's chroma upsampling hasn't been very good).

I did say rec.709 set it to 8bit . Rec.2020 is where the 10bit and HDR comes into play with HEVC. Since the Shield doesn't automatically switch colorspace like the Apple TV, you just have to be cognizant of what you're playing vs what the output is set at.

Now I will say that generally speaking since the 7.0+ update the Shield is actually doing a really good conversion from rec.709 to rec.2020. Before that is was horrible and colors were off. I can't tell a visible difference anymore, so you could realistically keep it set to '3840x2160 59.940 Hz YUV 420 10-bit Rec. 2020' in the Shield HDMI settings now and you shouldn't be able to tell that the colorspace conversion is happening.

Shasarak wrote: 09 Oct 2018, 21:22 4:2:0 10-bit YUV for rec.2020 poses a problem: it limits you to 50Hz, 59.94Hz or 60Hz refresh-rate, which will give 3:2 judder on 24fps film material. How much of an image quality hit do you get switching to 12-bit 4:2:2 rec.2020 instead?

No, not with MrMC (thanks to koying). It will automatically adjust the refresh rate and the resolution (I've only tested going from 4K to 1080p) but it works. There's no videos that I know of done at 12-bit 4:2:2 so there's really no reason to put that as your output.

edit to add: That WILL be the case with Netflix and Amazon Prime and other apps that don't do refresh rate and resolution switching like Netflix and Amazon Prime.

Shasarak wrote: 09 Oct 2018, 21:22 Good to know. As I recall, SPMC recommends RGB rather than YUV444, so clearly one shouldn't assume recommended settings for other Kodi forks apply here - hence why the question was an important one.

timstephens24 wrote: 09 Oct 2018, 21:52Generally most videos are done at YCbCr 4:2:0

Most? How many aren't?

timstephens24 wrote: 09 Oct 2018, 21:52so if you want you can do that instead of YCbCr 4:4:4 for rec.709 videos. You can also do RGB, there shouldn't be any issues doing that at all. It's just personal preference (or should be unless the Shield started messing something else up in the conversions) at that point.

(weary laugh)

Have you used an Nvidia shield much? Let me assure you, there is an easily-visible-to-the-naked-eye difference between playing a video with the output set to RGB and playing it with the output set to YUV 4:4:4.

Of course there shouldn't be - but there is. That is one of the reasons why I started this thread: given that RGB and YUV444 output aren't the same, I would like you guys to tell me which of the two is more accurate.

Another thing to say about the Shield is that its chroma upsampling is unusually poor: judging by some work with test images I did a while back, I think it probably uses a nearest-neighbour approach where most other devices use at least a bilinear one. The difference between outputting 4:2:0 (and having an external device doing the chroma upsampling), and outputting 4:4:4, is easily visible to a discerning eye.

But that doesn't necessarily mean 4:2:0 is the better option overall, because I don't know whether its YUV or RGB output is the more accurate....

Shasarak wrote: 09 Oct 2018, 21:22 Also interesting that you aren't recommending 4:2:0 8-bit in cases where the resolution and frame-rate supports it.

timstephens24 wrote: 09 Oct 2018, 21:52I did say rec.709 set it to 8bit .

You said 8-bit 4:4:4, you didn't say 8-bit 4:2:0.

timstephens24 wrote: 09 Oct 2018, 21:52Now I will say that generally speaking since the 7.0+ update the Shield is actually doing a really good conversion from rec.709 to rec.2020.

Hmm. We'll have to agree to disagree on that; the difference is extremely visible to me.

It's also worth noting that hardly any other device uses SDR rec.2020. Some TVs won't handle it correctly, and a calibrated screen likely won't be calibrated for SDR rec.2020.

Shasarak wrote: 09 Oct 2018, 21:22 4:2:0 10-bit YUV for rec.2020 poses a problem: it limits you to 50Hz, 59.94Hz or 60Hz refresh-rate, which will give 3:2 judder on 24fps film material. How much of an image quality hit do you get switching to 12-bit 4:2:2 rec.2020 instead?

timstephens24 wrote: 09 Oct 2018, 21:52No, not with MrMC (thanks to koying). It will automatically adjust the refresh rate

That's not strictly true.

If you have the colour space set to 10-bit 4:2:0 rec.2020, with refresh rate matching turned on, and you play a 24Hz video, it doesn't switch to 24Hz, 10-bit, rec.2020, 4:2:0; it switches to 24Hz, 12-bit, rec.2020, 4:2:2.

So, yes, the device isn't locked to 50Hz or over, but if everything you play is 24fps, you don't gain anything by choosing 4:2:0 10-bit in the first place.

Yeah that's why manually setting the display on the Shield is what I do (and why I hate the Shield). It's also why optimal settings on the Shield for some don't work for others, it's all in what you can perceive as accurate but most people don't notice a difference.

If you want some good insight into the color accuracy on the Shield, search for wesk05's posts on the Kodi forums in the hardware section. He's also posted here a few times, but his tests are way better than any I could do.

timstephens24 wrote: 10 Oct 2018, 23:29why I hate the Shield

Ah! A kindred spirit!

timstephens24 wrote: 10 Oct 2018, 23:29It's also why optimal settings on the Shield for some don't work for others, it's all in what you can perceive as accurate but most people don't notice a difference.

Is there no agreement on what is objectively the most accurate? Or is it simply that nothing gives you an accurate picture, and you have to fall back on subjective preference to choose between the different inaccuracies?

This is educated guesswork only, but I would have thought that a good approach might be to minimise the number of transformations between colour spaces. So, for example, if Kodi reverts a video image as an OpenGL texture in RGB space, it may be better to output the result as RGB; but if using MediaCodec(Surface) renders the video natively in YUV (and I'm not actually sure if it does or not!) then outputting YUV might work better...?

timstephens24 wrote: 10 Oct 2018, 23:29If you want some good insight into the color accuracy on the Shield, search for wesk05's posts on the Kodi forums in the hardware section. He's also posted here a few times, but his tests are way better than any I could do.

I will hunt those down.

We haven't talked about audio settings yet. Any traps to avoid there?