PAL Users - whats the advantage of the native 25p hack

N

nathankw

Well-known member
I've got a PAL GH1 and am loving the new higher bitrates.
But I've had some of the problems (freezing on static scenes, pulsing on i-frames) that seem to be due to the "native 24/25p" option.

I know native 24 is a big issue for NTSC users because of the difficulties going from 60i-24p. But is there much advantage for us PAL users of the native 25p?

I've not knowingly had any problems with 1080 50i footage (though my experience is limited as I've mostly shot 720 until now becaus of mud). It always seems to drop easily into a 25p timeline. So are we best off keeping it 50i? Or are there advantages to native 25?
 
Haven't experimented with it, but the two potential advantages would be:
1) slightly more efficient compression due to using progressive rather than interlaced encoding
2) better chroma recording, due to the better 4:2:0 progressive system instead of the wonky 4:2:0 interlaced recording.

But, that's theory; you'd have to test it to see if it really makes any difference.
 
nathankw said:
I've got a PAL GH1 and am loving the new higher bitrates.
But I've had some of the problems (freezing on static scenes, pulsing on i-frames) that seem to be due to the "native 24/25p" option.

I know native 24 is a big issue for NTSC users because of the difficulties going from 60i-24p. But is there much advantage for us PAL users of the native 25p?

I've not knowingly had any problems with 1080 50i footage (though my experience is limited as I've mostly shot 720 until now becaus of mud). It always seems to drop easily into a 25p timeline. So are we best off keeping it 50i? Or are there advantages to native 25?
Click to expand...

Why 25p ? because of better quality as already noted by Ian-T

I used both 1050 50i and 720 50p in the past for footage and both produced mud specially using the 20mm 1.7 Pana (don't ask me why.. I do not know...but a pan with the 20mm was almost always muddy)

Now using the 1080 25p i do not notice mud anymore using the 20mm.

I did not try using the c setting without the 25p option. But why to use a 50i instead of a sharper 25p ?

see my still image original vs hacked comparison on the AVCHD topic...
http://imageshack.us
 
I'm a bit confused as to why the GH1 1080 50i should be any sharper than 1080p25. Sure, if you originate something as interlaced and then turn it into progressive, you'll introduce artefacts and lower vertical resolution. But the GH1 samples at true 25p, it merely packaged this as 50i, pumping out one set of lines followed by the next set of lines from the same frame.
Turning this back into 25p is trivial and shouldn't reduce quality at all.

But I guess I should try it out.

Barry makes a good point about compression and whether it handles the 25p better.

As for mud, yes that's now gone (hurrah!) but I presume that's down to the increased bitrate rather than native 25p. Anyway, I'll do some testing and report back.
 
Nathan, I know what you are saying. I just tried running the jobless c settings last night. Massive improvement already, but that was without the native 25p option ticked. I'm going to try the 25p tonight and see if I can spot any discernible difference.
 
We'll I've had a go testing and can't say I can tell any difference.
Motion looked the same, and I can't see any picture quality difference.

Here's a frame grab showing with and without the native 25p option.
There's a colour difference but I think that's just that the sun came out.

Resolution and compression look the same to me. Obviously further testing needed but I think I'll stick with not using the native 25p option. It's much more stable without.

Dowload here:
http://www.4shared.com/photo/X9JI0ayi/gh1_25p_50i.html
 
Hello, I am a PAL user and I ask myself the question of native 25p too.
Switch native 25p that it makes us lose the ability to make 720 50p?
 
no the 24-25p option in ptool (so 25p for a PAL version) will only modify the 1080 50i, not the 720 50p
 
If i check the 24/25p Option an patch my PAL GH-1 i experience problems, like Card-Errors recording in Mjpeg-Mode. I turned this Option off now and all works fine.
 
With the "c" settings and 25p enabled, I experienced camera freezes and card errors, when shooting into the edge of a forest at f8 and above. No problems when I retried with this unchecked. So basically deeper focus with very fine detail is very demanding on the card/camera.
I haven't had time to do any more thorough testing yet, but has anybody else noticed a reduction in jello when 25p is enabled, or am I just imagining it?
 
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