Raspberry Pi4 4GiB 1080p120hz videoplayback extremely async

PiFan · March 19, 2021 at 1:42 PM

Hi,

I've got the following problem, which I wasn't able to solve on my own, using google:

I'm using LibreELEC 9.2.6 (also tried the current Beta 9.95.1) on a Raspberry Pi 4B 4GiB.

I tried to play self-recorded footage with 1080p and 120 fps (~10 MB/s overall bitrate). I play it over a smb-share from my NAS.

The sound is playing as expected (in terms of speed), but the video follows extremely slow (I guess with 30 fps) behind, so its not synced.

I first thought that the Pi might be to weak (in terms of cpu-power), but I was able to properly play the same files in the same way with kodi installed on an old (and much waker than the pi4) android tablet. Additionally I tried footage from youtube (with a much smaller overall bitrate) which had 50 fps and it shows a similar behaviour. Regular 30 fps videos work as expected.

Is there any option to sync video and audio which I didn't find ? Or any way to debug why its showing this behaviour ?

(The files and the network speed are okay. I played the same videos from my NAS on my laptop using vlc and mpv and both play them with perfectly synced audio / video.)

Thank you in advance.

**chewitt** · March 19, 2021 at 3:08 PM Official Post

In the new video pipeline modes above 85Hz should be hidden since the hardware decoder(s) are not expected to work at those frame rates (bitrate is one variable but not the main one). It looks like there may be some scenarios where >85Hz rates are still visible, but now the Pi Foundation devs are aware I'd expect that to change in the near-term future. TL/DR; not supported.

PiFan · March 19, 2021 at 3:21 PM

I'm not sure if I understand your correctly. Please define "video pipeline mode".

If I understand you the right way, playing videos with more than 85Hz is not supported. Does that mean its impossible to output them at >85Hz or is it possible to play a 120Hz video with 60 Hz, not showing every second frame ?

I didn't expect to be able to output the video with 120Hz (since the output tv has only 60 fps anyway).

**chewitt** · March 20, 2021 at 10:58 AM Official Post

Kernel drivers should see that 120Hz modes are available on the HDMI connection and filter them out so that userspace applications cannot see or use them.