[3DBuff]

Guys, anybody with any ideas? How accurate is RPi HDMI output refresh rate display in Kodi?
Is this possible for RPi to be set for 23.98fps and projector display at 24.00 at the same time. Would it work at all or one of them is not showing correct number?

From my post above, I'm just trying to understand discrepancy.

Any info on this subject would be appreciated.

[mk01]

@3DBuff

it is not a general rule that all devices do show the derived (NTSC) clocks in detail - instead just the PAL alternation is shown so

23.976 -> 24
29.970 -> 30
59.940 -> 60

[3DBuff]

I could agree with this if the projector was showing "Refresh Rate 24Hz"

But if you look at my pictures from the previous post you see that the same source material shows:
23.976 -> 24.00 Hz
and then
23.976 -> 23.97 Hz
All I need to do to flip the info screen is to reinitialize display (cause it to go back, loose the signal for a moment).

The frame on the bottom right hand corner is from projector showing the source. In both cases I'm playing the same video clip. Use the right arrow on the picture to see the codec info screen from Kodi player.

Everybody agrees that 24.00 and 23.976 are completely different standards. Why is projector mixing it up in the info section? Isn't there some sort of hand shaking going on between player and the display over HDMI to establish resolution, refresh, color depth, audio standards etc?

[popcornmix]

Everybody agrees that 24.00 and 23.976 are completely different standards. Why is projector mixing it up in the info section? Isn't there some sort of hand shaking going on between player and the display over HDMI to establish resolution, refresh, color depth, audio standards etc?

No the only difference between 24.00 and 23.976 is the pixel clock.
So to distinguish the modes the display will be counting clock cycles as as the difference is very small it may get these wrong.

If you want to be really sure what the Pi is outputting then you should use:

Code:

$ vcgencmd measure_clock pixel
frequency(29)=74175000

for 1080p23.976

Code:

$ vcgencmd measure_clock pixel
frequency(29)=74250000

for 1080p24
The numbers for 3D FP modes will be doubled.

measure_clock also counts clock cycles over a small interval, so results may vary a little, but it should be accurate enough to distinguish 23.976 and 24.

[3DBuff]

Thanks, I will try it tonight.

[3DBuff]

Popcornmix, thank you for explaining this concept. I was under the impression that the frame per second information on my projector signal info screen was taken from EDID tags.

After few tests it's clear that RPi is changing fps according to codec information. Projector is probably sampling pixel clock rate, but not too accurate or not as often as needed.

If I set the refresh rate in Kodi -> System -> Video to 24.00 Hz the menu display is at 24.00 Hz according to RPi "vcgencmd measure_clock pixel " command and projector info screen. When playing video clips encoded in 23.976 I can see screen going black and projector synchronizing to new refresh rate confirmed by "vcgencmd measure_clock pixel" command but the projector input signal info screen is quite often stuck in 24.00Hz from the previous sync.

I'm glad I got to the bottom of this. I can sleep better now

[noggin]

Popcornmix, thank you for explaining this concept. I was under the impression that the frame per second information on my projector signal info screen was taken from EDID tags.

Both 24.000 and 23.976Hz modes are treated as 'the same' under EDID - there aren't separate modes, and they aren't flagged as 'different' over HDMI. As popcornmix says, it's just the pixel clock that changes.

If only the people implementing NTSC chroma in the 50s hadn't felt the need to alter the field-rate (they couldn't alter line rate as B&W TVs were already in use designed for 525) to minimise feared interference between the broadcast colour sub-carrier and the sound sub-carrier... We've been cursed with the results (23.976, 59.94, drop frame time code etc.) ever since...

[meccs]

The other question is: what does your TV understand? If he can switch to 24Hz, does he know how to handle 23.976 content? The naming on TVs for that is very confusing too, like True Cinema mode etc. No wonder big companies like Apple/Amazon leave it at 2:3 pulldown because it just works and most people have no problem with it.

[3DBuff]

From what I understand now it looks like the player (blu-ray, Raspberry Pi, etc.) generates pixel clock refresh rate. The display (TV, projector etc.) follows this frequency. Under 24 frames per second the player and display can lower clock frequency to 23.976 fps to match source video. It looks like it is all up to the player to generate proper 23.976 unless your TV does not have 24 Hz capability at all and then it's back to 60 Hz with 2:3 pulldown.

It's easy with Raspberry Pi. Under system display you will have selection of frequencies to choose from including true 23.97 and separate 24 Hz unless your TV does not support this and you only see 60 Hz like my computer monitor.
When Raspberry Pi is connected to my Epson projector I get a full list of frequencies: 23.97, 24.00, 29.97, 30.00, 50.00,59.94 and 60.00Hz. Video files matched to display 1 to 1 will give perfect playback. Frame interpolation can further down reduce noticeable frame rate to smooth flowing image like 60 fps HD video cameras. I prefer watching movies at original 24 fps for the true cinematic experience.

Set your TV to True Cinema mode and check on Raspberry Pi if you can select 23.97.
After that use instructions from Popcortmix (previous posts) to verify Raspberry Pi pixel clock (refresh rate).

[3DBuff]

For those of you who are interested in refresh rates, frames per second and trying to get the best out of your system.

I managed to test shutter speed on my Epson and no name active 3D glasses. I used optical tachometer with ability to capture frequencies from 0.017 Hz (1 per min) to over 1.67KHz (99,999 per min).

Both sets of glasses are operating at the same speed 60Hz driven by projector RF transmitter when display is at 24 and 60 fps.
When display is switched to 23.97 and 59.94 I get 59.933Hz on both glasses. The readings are pretty consistent.

This would explain why when watching 24 fps video material in 3D with active glasses there is jitter present like the glasses were out of sync. This is probably more noticeable then the flicker itself from 60 Hz shutters in the glasses. I'ts not too bad when frame interpolation is to the max allowing glasses to synchronize on any high frequency frames.

[Prot0n]

I have my laptop (Intel HD Graphics 4000) connected via HDMI to my LG TV, that supports 24p @1080p.

I have enabled Adjust display refresh rate and now when I play a movie the image is much bigger that the screen, it dosent fit the TV size...

I've tried modifying TV settings but I haven't been able to find the solution so far..

Any idea what's happening here?

[3DBuff]

It sounds like you have different resolutions between laptop and TV screen. Try to select TV as your primary and only display in the laptop display properties. You will loose the image on the laptop screen but the TV should get back to proper size.
After this you should see you laptop desktop image on the TV screen. If something is not quite right like the "Start" button partially hidden blow TV frame then make adjustments in the TV menu to disable overscan or something similar.

To have laptop display and TV going on at the same time with different resolutions and frame rates is quite challenging. Most laptop won't do it.

[fritsch]

I have my laptop (Intel HD Graphics 4000) connected via HDMI to my LG TV, that supports 24p @1080p.

I have enabled Adjust display refresh rate and now when I play a movie the image is much bigger that the screen, it dosent fit the TV size...

I've tried modifying TV settings but I haven't been able to find the solution so far..

Any idea what's happening here?

Underscan - a setting of your TV. Set it to Fixed / Just Scan or whatever it is called.

[meccs]

I have my laptop (Intel HD Graphics 4000) connected via HDMI to my LG TV, that supports 24p @1080p.

I have enabled Adjust display refresh rate and now when I play a movie the image is much bigger that the screen, it dosent fit the TV size...

I've tried modifying TV settings but I haven't been able to find the solution so far..

Any idea what's happening here?

Most TVs Setting like "Fit to Screen" or "Fill Screen" do this. There should be a setting like "Original Size" that would zoom out and show 100% of the picture. You could also change the zoom in Kodi if you want to leave your TV at Fit to Screen for normal Television.

[wedok]

"Sync Playback to Display" is different.  It alters the playback speed so that it matches the display refresh rate (which could be fixed or could be variable if you have also selected Adjust Display Refresh Rate)

Hello,
i never really used Kodi but i'm planning to move my "Stuff" to one of those Amlogic S905 Android Media Player boxes.

What exactly happens when you use "Sync Playback to Display" together with Bitstream Audio?
Normally speeding up Video and keep the original Bitstream AC3/DTS, etc is impossible.
U get Audio Dropouts/Clicks, etc.

If it really works flawless with Kodi what exactly does Kodi do to make it work?

On Windows (with Directshow Mediaplayer like MPC-HC or DVBViewer) i use "Reclock" to speed up 23,976/24p Video to 25p.
The AC3/DTS Audio is decoded to 5.1, then also speeded up by Reclock and at the end finally (re)encoded by a Dolby Digital Live Soundcard back to an AC3 stream which is sent to my AV Receiver.