Kodi Community Forum

What happens if I'm playing a video file that has 24 FPS content but the HDMI output is set to 60 Hz?

Does XBMC perform 3:2 pulldown or what happens exactly?

3:2 pullup is applied as expected. 3 frames, 2 frames, 3 frames, etc. Most people can't tell since it's fairly normal on broadcast TV in the US.

Thanks for the information.

Is it better to have XBMC perform this or my TV?

I have two options:

1) Have XBMC output 24 Hz (which my TV accepts but then performs 3:2 pulldown)
2) Have XBMC output 60 Hz

Any idea which one is better?

It should look identical, but 60 hertz is better for performance, because the vsync limit isn't reached during video playback.

bobo1on1 Wrote:It should look identical, but 60 hertz is better for performance, because the vsync limit isn't reached during video playback.

I think it is not quite as simple as that. 24p (in this case actually 23.976p) streams should look most correct played at a display refresh (multiple) of 23.976Hz. Introducing 3:2 patterns is creating a small judder effect. Of course some people do prefer that look (as it is sometimes reported to make some motion effects inherent in 24p more pleasant), so personal preference should be applied.

Most displays will not do 23.976Hz as exactly that anyway, and instead will be a multiple of that but still advertised as 23.976 to the sender (graphics card/player etc). The point about the vsync limit though is valid, giving more room for small adjustments when perfect sync is a struggle.

EDIT: Oops I missed the point about the TV doing the 3:2 adjust internally anyway. Please ignore my post!

I'm sorry for asking so many questions, but what are you guys talking about regarding vsync? (I know that vsync is only updating the display on the vertical sync [to avoid tearing] but I'm not sure how it relates to this topic...)

sofakng Wrote:I'm sorry for asking so many questions, but what are you guys talking about regarding vsync? (I know that vsync is only updating the display on the vertical sync [to avoid tearing] but I'm not sure how it relates to this topic...)

Just really means the refresh rate presented to computer, ie one vsync between each refresh. Thus if xbmc is struggling to present a video frame in time for when it should be presented it can be displayed at the next vsync...with 60Hz that gives more granularity to adjust. If playback is stable then there should be no difference. Note it could be argued in the opposite way too, that there would be more load on xbmc handling more vsyncs. Either way consider the difference very small.

Thanks so much for the information everybody.

I was all concerned with getting 24 Hz output (following the guide on this forum, etc) and it turns out my TV only supports 60 Hz so I won't be using it anyways. (I did try 48 Hz and the flicker really did make it unwatchable...)

So, if I am noticing xbmc dropping frames ie. fps constantly below 24 when the bit rate rises...do i need to adjust the monitor/tv's profile. Having already tried to disable and able sync to display as well as av sync without luck.

TheSwissKnife Wrote:Just really means the refresh rate presented to computer, ie one vsync between each refresh. Thus if xbmc is struggling to present a video frame in time for when it should be presented it can be displayed at the next vsync...with 60Hz that gives more granularity to adjust. If playback is stable then there should be no difference. Note it could be argued in the opposite way too, that there would be more load on xbmc handling more vsyncs. Either way consider the difference very small.

Actually the load for XBMC is pretty much identical, it will only render as fast as the video fps, no matter what the refreshrate is (as long as it's higher).

activate Wrote:So, if I am noticing xbmc dropping frames ie. fps constantly below 24 when the bit rate rises...do i need to adjust the monitor/tv's profile. Having already tried to disable and able sync to display as well as av sync without luck.

That sounds like a decoder issue, it's unrelated to the refreshrate.

bobo1on1 Wrote:Actually the load for XBMC is pretty much identical, it will only render as fast as the video fps, no matter what the refreshrate is (as long as it's higher).

Only tiny... but the reference clock is working harder with Wait function trying to ensure it meets the target time without missing event, and each VSYNC updating the clock. I didn't mean to imply it rendered faster.