Problem with converting .mts 1080 50i and keeping it 50fps

[gf3user]

Hi Guys

Been struggling for days on this. I have recently bought a Pansonic GF3 and filmed a lot of footage at the AVCHD 1920x1080 50i, I've been trying to convert the .mts files so I can actually have a file which is 50 frames per second, however whenever I do it either turns out as 25 fps if i set it to automatic, or if i set it manually to 50.. it skips frames and is practically 25fps. I've tried loads of conversion tools, nothing seems to work, which makes me think im either doing it wrong, or something about the footage.

I've uploaded a test file for any helpful people out there.
http://dl.dropbox.com/u/1273700/00073.MTS

Any ideas what I need to do to keep my files truly 50fps? Thanks guys!
Josh

[aedipuss]

your 50i is 50 fields per second, not 50 frames per second. it takes 2 fields to make a frame so it's really 25fps.

[manono]

Any ideas what I need to do to keep my files truly 50fps?

It's not truly 50fps. It's truly 25fps. And to elaborate on what aedipuss said, it's not even 50 unique fields per second, but each field pair is from the same point in time. The content is progressive but it was only encoded as interlaced..

[jagabo]

Use a smart bob doubler to convert 25i into 50p.

[gf3user]

Thanks for the reply guys.

I realised that it was not true 25fps, but thought I could create 50fps from 50i using a de-interlacer. Thanks jagabo, will try the smart bob doubler. Know any good products for a mac?

[poisondeathray]

But it is true 25 fps, as manono said above.

True 50i means 50 fields per second. Each field is unique moment in time. You could then use a double rate deinterlacer to generate 50p

But you don't have that. You have 25p encoded as 50i. This is 25p progressive content encoded as interlaced . (You only have 25 moments in time per second represented; i.e. consecutive fields represent the same moment in time)

I suspect you shot in the wrong mode.

One way you could generate 50p is use motion interpolation e.g. twixtor, after effects, where new "in between" frames are generated, but it's time consuming and often there are problems with edge morphing artifacts

[jagabo]

Ah, I didn't download the file. I assumed it was really 25i as the OP claimed. After downloading, I agree. It's 25p frames encoded as 25i.

[gf3user]

You are super helpful poisondeathray, I thought as much as the footage didnt have any interlacing which my friends footage from the GH2 had.

Think I will have to shoot in 720 to get the 50fps I want. Thanks!

[jagabo]

Think I will have to shoot in 720 to get the 50fps I want. Thanks!

According to this review 720p50 is also 25 fps (frames repeated).
http://www.dpreview.com/reviews/panasonicdmcgf3/

[gf3user]

Thanks for looking into it Jagabo.. that's gutting.. and shows my lack of understanding about this all.

So just to be double sure (and to probably show my lack of understanding again), the 720 is 50p, I thought that would mean that it is not interlaced, and actually 50fps... ?

Might have to sell this camera if thats not the case, really want something that shoots faster than 25fps. Not a huge fan of the twixtor effect.

[jagabo]

So just to be double sure (and to probably show my lack of understanding again), the 720 is 50p, I thought that would mean that it is not interlaced, and actually 50fps... ?

According to dpreview the camera's 720p50 output is from a 25 fps sensor with the frames doubled. So there are only 25 different pictures per second.