Login at Kodi Home

ringgh0st · 2009-10-27, 11:10

since i use xbmc @ a x86 plattform i have issues with smooth movies. i never realised why it happens that a movie seems to stutter when playing.

i always think that movies dont play really smooth like on my laptop althoug i have better pc hardware (core quad q6600)

i read over and over but never got a useful answer (which i understand. im not that familiar with ntsc and pal and halfpictures and fps).

i run xbmc @ win7, latest SVN on a panasonic plasma 42" through DVItoHDMI (720p@50Hz)

yesterday i tried (while onscreen errorlogging was enabled) again some different setups and voila i imagined something really interesting.

when i watch a movie with DIGITAL AUDIO (SPDIF, AC3, DTS = ON) switched on, the framerate goes down to exact 24 fps (CPU load max 8%, movies stutters a little bit).

when i switch DIGITAL AUDIO off the framerate goes up to 25ps and everything runs really smooth.

what can i do? does anyone also have this issue? How can i fix it?

kulprit · 2009-10-27, 12:49

I would say you have sync playback to display turned on with one of the settings that doesn't work with passthrough. Change the sync playback to display from audio clock/resample to drop/dupe audio and see if that means you get 25fps all the time.

If i've got the settings wrong someone please correct me. The video you are playing is actually a 24fps video, but xbmc is speeding it up along with the audio so that it matches the refresh rate of your screen, making it look smooth.

ringgh0st · 2009-10-27, 14:51

kulprit Wrote:If i've got the settings wrong someone please correct me. The video you are playing is actually a 24fps video, but xbmc is speeding it up along with the audio so that it matches the refresh rate of your screen, making it look smooth.

...because 24fps isnt smooth on a 50Hz display isnt it? For smooth Playback i need 25fps!

ill try tonight when im at home. thanx for your hints.

**neil.j1983** · 2009-10-27, 15:28

ringgh0st Wrote:...because 24fps isnt smooth on a 50Hz display isnt it? For smooth Playback i need 25fps!

ill try tonight when im at home. thanx for your hints.

you cannot bitstream and speedup by 4%, xbmc will be dropping bits of audio all over the place.

your far better off connecting via analog and resampling the audio.

if thats not possible, a DDL or DTS Connect card is a good alternative.

ringgh0st · 2009-10-27, 15:32

but why do i only have this problem? there should many many ppl out there with SPDIF audio and a PAL system?

strange

**bobo1on1** · (This post was last modified: 2009-10-27, 16:14 by bobo1on1.)

You have turned on "sync playback to display" and set the synctype to resample, your refreshrate is 50 hertz and you're playing a 24 fps movie.

XBMC detects all that, and then decides to play the file at 25 fps, because XBMC knows what's good for you.

The reason why this doesn't work with passthrough (only passthrough, analog and pcm over hdmi/spdif are ok), is because the speedup requires resampling, and you can't resample compressed audio, you have to decode it, resample it and then encode it again.

Since XBMC currently lacks an ac3 encoder, it will fall back to drop/dupe whenever resample is selected and passthrough is used.

Your best option would probably be to use a refreshrate of 24 or 60 hertz.

ringgh0st · 2009-10-27, 16:18

bobo1on1 Wrote:You have turned on "sync playback to display" and set the synctype to resample, your refreshrate is 50 hertz and you're playing a 24 fps movie.

XBMC detects all that, and then decides to play the file at 25 fps, because XBMC knows what's good for you.

The reason why this doesn't work with passthrough (only passthrough, analog and pcm over hdmi/spdif are ok), is because the speedup requires resampling, and you can't resample compressed audio, you have to decode it, resample it and then encode it again.

Since XBMC currently lacks an ac3 encoder, it will fall back to drop/dupe whenever resample is selected and passthrough is used.

Your best option would probably be to use a refreshrate of 24 or 60 hertz.

so when i set the tv to 60 Hz it should work you mean? May i ask why? 24x2= 48 Hz Wink

**bobo1on1** · 2009-10-27, 16:34

Playing 24 fps at 60 hertz creates a judder effect, which is far less annoying than the jerks you get by playing 24 fps at 50 hertz.

If you're lucky your tv can even do a pulldown and the judder will be gone.

ringgh0st · 2009-10-27, 16:43

k mates. ill try tonight but i think i'll try the sync way with analog audio (although i have a really cool 5.1 stereo at home Wink

)

my plasma does have a huge overscan @ 60Hz, thats why i prefer 50Hz. Seems that i have to invest for a new one. LOL

but it only happens, when i watch movies with 24fps rate. is this the usual US-encoding format?

**bobo1on1** · 2009-10-28, 20:43

24 fps is how they are originally recorded and shown in the cinema.

ringgh0st · 2009-10-28, 21:14

bobo1on1 Wrote:24 fps is how they are originally recorded and shown in the cinema.

ok. so every PAL looking guy with DIGITAL AUDIO = enabled has my problem?

Nick8888 · 2009-10-28, 22:18

I'm pretty sure I've got this issue too. Only seems to do it with vdpau. Ill have to check my refresh rate when I get a chance.

ringgh0st · 2009-10-29, 00:01

after a lot of testing now i know:
720p/60Hz doesnt solve my stuttering problem. xbmc tries to get smooth framerate but it isnt really a alternative to the standard 720p/50Hz.

i will now use 720p50 and analog audio out. because THIS IS DEFINITLY SMOOTH VIDEO.

if anyone has another workaround to get digital audio smooth working feel free to paste it here.

anyhows XBMC rocks Wink

**Hitcher** · 2009-10-29, 00:14

Nick8888 Wrote:I'm pretty sure I've got this issue too. Only seems to do it with vdpau. Ill have to check my refresh rate when I get a chance.

There's no VDPAU in the Windows builds.