[RPi5] Refresh Rate Problem on Optoma CinemaX D2 Projector

    Hi All,

    I am using 4K projector which supports those movie oriented refresh rates like 23.98, 29.97 and 59.94. My problem is that if movie is 23.98 fps then Kodi sets refresh rate on my projector to 24Hz. When i change it to 29.97 it rounds it to 30. 59.94 rounds to 60. I have also tried to change the 'general' refresh rate which stays even in menu but it behaves the same.

    The refresh rate i am interested fixing the most is 23.98 as most of my movies are 23.98 fps. Is there anything i can fix/tweak to force Kodi to use 23.98Hz refresh rate properly?

    I am using RPi5 on LE 12.0.2 (120.1 was the same issue). My projector is Optoma CinemaX D2. Original Raspberry Pi HDMI cable (tried different high quality cable with adapter - the same problem).

    When I connect my Windows PC to that projector and set manually 23.98Hz refresh rate then my projector switches to 23.98Hz properly so it seems to be only issue with my LE box which rounds the refresh rate.

    I would really appreciate any help in this matter.

    If you are connecting the project through an AVR, remove it from the HDMI chain and connect direct to confirm things working as expected (then blame the AVR). If not doing that, put Kodi into debug mode, reboot, demonstrate the issue with 23.976 media, then run "pastekodi" and share the URL so we can see the DRM modes available and what Kodi selects.

    Thank you for your reply.

    My RPi is directly connected to the projector via HDMI cable. I have created the logs:

    https://paste.libreelec.tv/caring-moray.log

    Frame rate of the movie extracted from MediaInfo:

    Frame rate                               : 23.976 FPS

    After starting movie, projector switched to 24Hz refresh rate.

    Kindly please examine and let me know if there is anything that can be done in my case.

    Code
    2025-01-24 08:35:39.301 T:986      info <general>: Opening stream: 0 source: 256
2025-01-24 08:35:39.301 T:986      info <general>: [WHITELIST] Searching the whitelist for: width: 3840, height: 2160, fps: 23.976, 3D: false
2025-01-24 08:35:39.301 T:986     debug <general>: [WHITELIST] Searching for an exact resolution with an exact refresh rate
2025-01-24 08:35:39.301 T:986     debug <general>: [WHITELIST] Matched an exact resolution with an exact refresh rate 3840x2160 @ 23.976025 Hz (32)
2025-01-24 08:35:39.301 T:986      info <general>: Display resolution ADJUST : 3840x2160 @ 23.976025 Hz (32) (weight: 0.000)

    This ^ shows Kodi correctly detecting and selecting the [email protected] mode.

    Code
    2025-01-24 08:35:39.659 T:899     debug <general>: CDRMUtils::SetMode - found crtc mode: 3840x2160 @ 24 Hz

    This ^ means some code is rounding the value to 24Hz. I'm not sure if it's Kodi or the underlying kernel DRM layer, but I see the same on an LG TV and I have no playback issues, so this can be ignored.

    I can see from the log that you didn't whitelist any 1080p modes. That's probably a bad idea, but not related to this issue. Have a read of the wiki acticle here for recommendations: https://wiki.libreelec.tv/configuration/4k-hdr

    If seeing bad values in the log wasn't the issue? - how do you determine the projector is at 24Hz?

    Quote from chewitt
    Code
    2025-01-24 08:35:39.301 T:986      info <general>: Opening stream: 0 source: 256
2025-01-24 08:35:39.301 T:986      info <general>: [WHITELIST] Searching the whitelist for: width: 3840, height: 2160, fps: 23.976, 3D: false
2025-01-24 08:35:39.301 T:986     debug <general>: [WHITELIST] Searching for an exact resolution with an exact refresh rate
2025-01-24 08:35:39.301 T:986     debug <general>: [WHITELIST] Matched an exact resolution with an exact refresh rate 3840x2160 @ 23.976025 Hz (32)
2025-01-24 08:35:39.301 T:986      info <general>: Display resolution ADJUST : 3840x2160 @ 23.976025 Hz (32) (weight: 0.000)

    This ^ shows Kodi correctly detecting and selecting the [email protected] mode.

    Code
    2025-01-24 08:35:39.659 T:899     debug <general>: CDRMUtils::SetMode - found crtc mode: 3840x2160 @ 24 Hz

    This ^ means some code is rounding the value to 24Hz. I'm not sure if it's Kodi or the underlying kernel DRM layer, but I see the same on an LG TV and I have no playback issues, so this can be ignored.

    I can see from the log that you didn't whitelist any 1080p modes. That's probably a bad idea, but not related to this issue. Have a read of the wiki acticle here for recommendations: https://wiki.libreelec.tv/configuration/4k-hdr

    If seeing bad values in the log wasn't the issue? - how do you determine the projector is at 24Hz?

    Thanks for your explanation and pointing the whitelisted modes.

    Answering you question about how do i know that projector works in certain refresh rate, everytime i change resolution or refresh rate, my projector shows a little informational rectangle in the lower right corner with resolution and refersh rate it is currently operating on. When i set 23.98 on my Windows PC it show 23Hz, when i switch to 24Hz it shows 24Hz and so on.

    Quote from 4k3or3et

    When i set 23.98 on my Windows PC it show 23Hz

    The firmware in the projector has some rounding logic for display then, and when Kodi sends 23.976 it's showing you 24Hz. The Windows PC may not be using 100% the same modeline as Linux (different code, different calculations) and this could explain why one OS results in the firmware rounding down to 23 and the other results in rounding up to 24. I was going to make a comment on this being possible in the previous post, but chose to wait and let you explain first.

    The real-world test is: do you see periodic sync glitches during playback, or is playback smooth?. If you don't (and I suspect you don't with well prepared media) there's no issue.

    Glitches you are talking about I always test on the very fist scene of The Martian movie where the scene shows landscape of planet Mars. I just played that scene several times and I do not see any frame sync issues, playback was buttery smooth, so it must be what you are talking about with the rounding. Thanks again for you investigations.