How does XBMC determine correct refresh rate?
#1
I'm using one of the more recent SVN builds, and I've clicked on the "Adjust refresh rate" option in video player settings.

It switches most of my videos to 24hz. I've noticed a couple that play at 60hz. This is fine, but I'm just curious how XBMC determines what refresh rate to use. Does it switch because the source file is 24hz, or because of something generic such as the codec or resolution?

Mostly I'm wondering if this is something I need to think about when I'm encoding video.
Reply
#2
Source file framerate is what it switches on.

The 60Hz switch is likely due to 30fps source material.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


Image
Reply
#3
Is the roadmap wrong?

It says:

Code:
# 23.976FPS 720p (1280x720) playback at 23.976Hz
# 24FPS 720p (1280x720) playback at 24Hz
# 25FPS 720p (1280x720) playback at 24Hz
# 29.97FPS 720p (1280x720) playback at 29.97Hz
# 30FPS 720p (1280x720) playback at 24Hz
# 23.976FPS 1080p (1920x1080) playback at 23.976Hz
# 24FPS 1080p (1920x1080) playback at 24Hz
# 25FPS 1080p (1920x1080) playback at 24Hz
# 29.97FPS 1080p (1920x1080) playback at 29.97Hz
# 30FPS 1080p (1920x1080) playback at 24Hz

I am specifically wondering why 30FPS would play at 24Hz ? I imagine that TV produced for NTSC is actually recorded at 30Hz and should be played at 30Hz? The 25fps at 24Hz is also weird, imo, since PAL format TV would be recorded in 25fps!
Reply
#4
No idea where you got that info. Perhaps you could give us a link?
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


Image
Reply
#5
http://trac.xbmc.org/roadmap

Smile
Reply
#6
I think the 25-->24 ones are to cater for artificially accelerated 24fps material, that gets accelerated by 4% to play at 25fps.

Lots of movies and TV series coming from the States suffer from this, leading to the dreaded "chipmunk effect" where actors' voices sound unnaturally high pitched.

30fps at 24fps is referring to inverse telecine processing, where you detect the 3:2 cadence and reconstruct 24 frames per second out of the 30 frames per second that are generated by playing back each even frame twice and each odd frame thrice.
Reply
#7
I dunno how to edit the roadmap, but suffice to say it is probably just a typo. I doubt we'll get anywhere near most of that for 9.04. It's more of a wishlist than anything that will actually bear out in reality. I doubt we're going to implement any such cadence detection for quite some time.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.


Image
Reply

Logout Mark Read Team Forum Stats Members Help
How does XBMC determine correct refresh rate?0