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Hd Output At 50hz. Is It Possible?


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#1 bobbyblaze

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Posted 06 March 2007 - 09:51 PM

Is there a way of forcing the HD output of the xbox to 50hz for those of us in PAL land (sorta like a powerstrip for the PC) or are we doomed to watch upscaled DVD in stutter-vision forever?

Tens of thousands of xbmc users in Europe and Australia need to know.

#2 Jezz_X

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Posted 06 March 2007 - 10:27 PM

no its not possible but just convert your xbox to ntsc if it bugs you that much. Its as simple as runnign a program

#3 Bomb Bloke

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Posted 06 March 2007 - 11:35 PM

NTSC still displays at 60hz, and many TVs in this region just don't support anything higher then 50.

I think the solution is to re-encode the DVDs in concern.

#4 bobbyblaze

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Posted 06 March 2007 - 11:41 PM

Hi,
most tv's support 60hz and re-encoding doesn't solve the problem of having 50hz material displayed at 60hz (juddering pans and the like).

Just wondered , now that the xbox1 has been poked around with enough, if anyone out there had found a way to change the output of the graphics chip in there to something more video friendly. This would benefit NTSC users as well because if the xbox could be forced to output 71.928hz or 47.952hz it could do a reverse 3:2 pull down and remove telecine judder from 24fps film material. And a mighty big feather in XBMC's cap it would be. biggrin.gif

Edited by bobbyblaze, 06 March 2007 - 11:42 PM.


#5 pike

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Posted 07 March 2007 - 02:45 AM

I don't *THINK* this is hardware related.
Instead it's the Microsoft kernel that simply doesn't have PAL HDTV support. It may be possible to amend this, but that's the extent of my knowledge on this subject.

But seeing as Xbox Bios development died 1-1.5years ago (In a buggy state it was left), I don't have much hope of ever seeing something like this ever worked on by the 'skilled people'.

#6 Geeba

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Posted 07 March 2007 - 10:15 AM

QUOTE(bobbyblaze @ Mar 6 2007, 08:58 PM) View Post

Is there a way of forcing the HD output of the xbox to 50hz for those of us in PAL land (sorta like a powerstrip for the PC) or are we doomed to watch upscaled DVD in stutter-vision forever?

Tens of thousands of xbmc users in Europe and Australia need to know.


Yup I must agree... since treating myself to a Huge HD TV and getting my hands on a HD pack from the US... upscaled content is stating to not only anoy me its sending me giddy with the stutter-vison effect!!!!

Love my XBMC to bits! biggrin.gif but I must admit I've even started to price Media Centre PC coz of this..... sad.gif

#7 Jezz_X

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Posted 07 March 2007 - 10:54 AM

Just convert your xbox to NTSC is really has no ill effects and it can still play PAL games and watch pal movies

#8 Geeba

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Posted 07 March 2007 - 11:13 AM

QUOTE(Jezz_X @ Mar 7 2007, 10:01 AM) View Post

Just convert your xbox to NTSC is really has no ill effects and it can still play PAL games and watch pal movies


Yeah I have done that... its the only way HD resolutions are available.... xbmc is set to 720p 16/9 NTSC and output upscale resolution is set to 720p, TV detects 720p also but panning in movies is still stutter-vision... really wierd looking... at first I thought it was a cache or network server issue, but it only happens on panning movments. sad.gif

#9 bobbyblaze

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Posted 07 March 2007 - 03:04 PM

QUOTE(Geeba @ Mar 7 2007, 09:22 AM) View Post

Yup I must agree... since treating myself to a Huge HD TV and getting my hands on a HD pack from the US... upscaled content is stating to not only anoy me its sending me giddy with the stutter-vison effect!!!!

Love my XBMC to bits! biggrin.gif but I must admit I've even started to price Media Centre PC coz of this..... sad.gif



QUOTE(Jezz_X @ Mar 7 2007, 10:01 AM) View Post

Just convert your xbox to NTSC is really has no ill effects and it can still play PAL games and watch pal movies


PAL is 50 frames per second and the output of the xbox in either HD format is 60 frames per second. In order to synchronise this XBMC will repeat 1 in 5 frames which is becomes really obvious when the camera pans.

Considering all the amazing things an xbox with xbmc can do, if we could get it to become a true scaler which can alter frames per second output as well as resolution it would become the equivalent of an ISCAN HD scaler which costs several hundred dollars. The hardware is there, let's use it.

At the moment, the only real option for the thousands of PAL users is to buy an xbox 360 which (with a recent kernel update due to complaints) will allow 50hz 720p, 1080i&p but only for watching dvd/hddvd. As I mentioned above, this doesn't just effect PAL users. All NTSC film material repeats 1 in 4 frames as well to synchonise 24fps film material to NTSC frame rates. NTSC users also get juddering pans but they are just simply used to watching them unlike PAL users who normally receive a 4% speedup but no repeated frames. If 48 or 72 hz was an option for them they'd be amazed at how smooth it looked. It's very cinematic.

As it seems this is a kernel (bios?) thing should this topic be moved to a more relevant forum? Perhaps the bods at Team Xecuter could have a crack or someone else who wants the Kudos?

Edited by bobbyblaze, 07 March 2007 - 03:07 PM.


#10 Spaceman2004

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Posted 07 March 2007 - 04:02 PM

I'm not sure the xbox is up to it anyways.

Edited by Spaceman2004, 07 March 2007 - 04:09 PM.


#11 sheepie

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Posted 07 March 2007 - 07:38 PM

what do you mean by stutter?

#12 bobbyblaze

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Posted 08 March 2007 - 12:33 AM

QUOTE(Spaceman2004 @ Mar 7 2007, 03:09 PM) View Post

I'm not sure the xbox is up to it anyways.


If the xbox can ouptut 720/60p then I'm pretty darn sure it can output 720/50p & 720/48p (actually 47.952 fps). Don't know about 72hz but 48 would still be much better for 24 fps material.


QUOTE(sheepie @ Mar 7 2007, 06:45 PM) View Post

what do you mean by stutter?


A small excerpt from the lengthy wikipedia article that deals with the telecine process.

"3:2 pulldown

The process of converting 24 frame/s material to 29.97 frame/s is known as 3:2 pulldown. The term "pulldown" comes from the mechanical process of "pulling" the film down to advance it from one frame to the next at a repetitive rate (nominally 24 fps). This is accomplished in two steps. The first step is to slow down the film motion by 0.1%. This speed change is unnoticeable to the viewer, and makes the film travel at 23.976 frame/s.

The second step of the 3:2 pulldown is the 3:2 (or 2:3, see below) step. At 23.976 frame/s, there are 4 frames of film for every 5 frames of NTSC video:

These four frames are "stretched" into five by exploiting the interlaced nature of NTSC video. For every NTSC frame, there are actually two complete images or "fields," one for the odd-numbered lines of the image, and one for the even-numbered lines. There are, therefore, ten fields for every 4 film frames, and the telecine alternately places one film frame across two fields, the next across three, the next across two, and so on. The cycle repeats itself completely after four film frames have been exposed, and in the telecine cycle these are called the "A," "B," "C," and "D" frames, thus:

IPB Image"

This is how 480/30i & 1080/30i video is displayed by XBMC for NTSC users. As you can see the process of making 5 frames from 4 results in 2 of those frames looking like garbage. In progressive mode (480 & 720p/60) instead of garbled frames, each frame is repeated twice but one in four frames is repeated four times eg.

A B C D at 24fps
becomes
A,A,B,B,C,C,D,D,D,D at 60fps

When the camera is panning this is especially noticeable as the duration of one in four frames is twice that of the three proceeding frames. As this actually occurs 12 times a second it causes what would originally be a smooth pan at 24 frames per second to stutter quite badly when converted to 60 fps. If the xbox allowed 48hz output (or 72 if possible) then each frame of a 24fps movie could be repeated twice (or 3 times for 72hz) and there would be no garbled or superfluous frames. This is the sort of thing that home cinema freaks specifically use HTPC's or expensive scalers to reproduce and would be a massive feather in the cap[ of XBMC if the kernel could be enabled to allow it.

The same thing is happening to PAL users who wish to use XBMC to upscale DVD's. Our native frame rate is 25fps which is close enough to 24 fps that no repeating of information (or stuttering )is necessary. Our video is simply sped up by 4% and maintains the exceptionally smooth movement of its cinema cousin. As the xbox only recognises 60hz HD modes instead of our native 50 hz (where each progressive frame at 25fps would be repeated twice) we get 60hz instead and this means repeating 1 in 5 frames causing all the same problems that have been explained above. Due to massive complaints microsoft enabled 50hz HD output when using 50hz DVD or HD DVD on the 360 in the Autumn 1080p kernel update but, for some reason, didn't bother to enable 71.928hz for you NTSC users to get silky smooth film-like playback from NTSC material.

We all know what a great bit of kit the xbox is and XBMC absolutely wipes the floor with the crippled media capabilities of the 360. Given the way that it has been cracked open to such a great extent it would be great if this feature of flexible frame rates to match 24 or 25fps could be enabled as it would be a massive feather in XBMC's cap. Full blown scaler capability. At the moment 60hz doesn;t do anyone any favours, where ever you're from.

Edited by bobbyblaze, 08 March 2007 - 12:37 AM.





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