Is smooth playback a reachable end-goal for all platforms?
#1
Hi, in the past few months I've followed closely the development of the different versions of XBMC.

I wanted to have some developers views on this subject. On Windows, at least, Reclock becomes a necessity if you really care about a judder-free experience, what with all the different clocks in your PC fighting over control (video, CPU, audio, motherboard, etc.). Then there's the matter of vsynch that, Reclock aside, has been solve probably only by Vista+EVR.

I'm not familiar enough with Linux or Mac to say if this is not a problem over there, but my one installation of Ubuntu (for XBMC) pointed out at the same problems being very much there.

Now, I hope that this can be the right place to discuss how XBMC developers intend to tackle the problem, if they do.
Thanks for your time and attention and thanks for trying to bring this awesome product into the future. Nod
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#2
either reclock provides a high precision timer (which we already have). in this case what you need to do is switch output frame rates to match the video fps (this is wip).

otherwise reclock changes the samplerates leading to that lovely helium effect (we already have this feature, not sure if it's active on non-xbox platforms yet though).

so i dont see what reclock would offer at all. finally reclock is a dshow filter...
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#3
Hi spiff and thanks for answering.

I wasn't suggesting to use Reclock, I understand it's a dshow thing, hence a no go. From what I understand, Reclock does three things:

1) It attempts to provide a unified clock and/or harmonize the different clocks working in your machine (videocard, soundcard, motherboard, cpu, something else I might be forgetting...).
2) In doing so, it can slightly alter the samplerate, a minimal alteration to behave well with all the clocks, as per 1 above. No helium effect, we are talking really minimum adjustments here.
3) It's capable of either going 24fps-->25fps for those with 50Hz TV sets that want to avoid judder (or those with 50/60 who prefer a 4% helium effect to the 3:2 judder) or going 25fps-->24fps for those with 24/48/72/96Hz displays that want to bring back artificially accelerated PAL material to the original pitch. I don't think this function is enabled yet outside of the Xbox platform.

On the subject of high precision timer, which you mention, could you go more in depth in explaining what timer is been used?

Thanks. Smile
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#4
I'm personally not a fan of reclocking the video and changing the audio to get smooth playback. Proper pulldown involving adding extra frames in smart ways (telecine methods) is prefered to keep the audio where it should be. However in the case of film -> PAL 4% difference might not be too bad if prefered.

I would like to know if proper 24fps -> 30fps 3:2 pulldown is being worked on. The current implementation (anyone know what that is exactly?) leaves me with remarkably jerky playback of film based content (any new DVD movie I've tried). Specifically if there's a way to do it on the AppleTV platform. And unfortunately there doesn't seem to be a way to make the AppleTV display the proper 1080p/24hz input my Sony TV is expecting (like it would get from Blu-Ray) so that the refresh rate matches the framerate.

I think the main reason it bothers me so much is because the AppleTV, without XBMC, is remarkably capable of producing smooth playback with their QuickTime implementation.

Any further information is greatly appreciated.
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#5
The reclock feature exists on XBMC for Xbox. It would be great if it would be implemented for Windows to.
I created a ticket for it in august, it has been added as an feature request.
http://trac.xbmc.org/ticket/4689
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#6
ashlar Wrote:Hi spiff and thanks for answering.

I wasn't suggesting to use Reclock, I understand it's a dshow thing, hence a no go. From what I understand, Reclock does three things:

1) It attempts to provide a unified clock and/or harmonize the different clocks working in your machine (videocard, soundcard, motherboard, cpu, something else I might be forgetting...).
2) In doing so, it can slightly alter the samplerate, a minimal alteration to behave well with all the clocks, as per 1 above. No helium effect, we are talking really minimum adjustments here.
3) It's capable of either going 24fps-->25fps for those with 50Hz TV sets that want to avoid judder (or those with 50/60 who prefer a 4% helium effect to the 3:2 judder) or going 25fps-->24fps for those with 24/48/72/96Hz displays that want to bring back artificially accelerated PAL material to the original pitch. I don't think this function is enabled yet outside of the Xbox platform.

On the subject of high precision timer, which you mention, could you go more in depth in explaining what timer is been used?

Thanks. Smile
I bump this. Recent external player developments allow me now to use Zoom Player and Reclock. But the objective is, at least for me, to have DVDplayer handling everything (I think the developers see it this way too, clearly).
Even working at 48Hz, with 24fps material, XBMC stutters sometimes (not losing frames, mind). With Reclock I avoid that in DirectShow based players.
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#7
dan1son Wrote:I'm personally not a fan of reclocking the video and changing the audio to get smooth playback. Proper pulldown involving adding extra frames in smart ways (telecine methods) is prefered to keep the audio where it should be. However in the case of film -> PAL 4% difference might not be too bad if prefered.
Keep in mind that, at least for me, the objective is getting 25-->24 for 24fps material that's been accelerated to accomodate PAL users *and* getting silk smooth playback of 24p material when watching at exact multiples (24Hz, 48Hz, 72Hz, etc.).
I'm no fan of 24-->25 either (even thoug, for some people, it's the only way to get smooth playback and I respect that).
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Is smooth playback a reachable end-goal for all platforms?0