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Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)

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Dave Osbun
Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 8, 2014 at 2:41:44 pm

Please keep in mind that I don't have the video expertise that all of you have, and I don't shoot video for $$.

My camera (Sony NEX-VG10) supposedly shoots 30p but in a 60i wrapper. I never concerned myself with this because I always shoot with the settings set to its highest and keep the shutter speed at 1/60, and have been very happy with the results. However, today I went into one of my event properties and it showed the clip as 29.97 interlaced, upper field first. As a test I changed it from upper field first to progressive, and played it back in the trimmer to see if it looked any different, but it did not-- it looked exactly the same.

So i'm confused. If my camera records in 30p but in a 60i wrapper (which I don't understand), why does Vegas show it as interlaced??

Dave


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Dave Osbun
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 8, 2014 at 3:00:02 pm

To add to my above post: could it be 'Progressive Segmented Frame', which is how my camera records 30p, causing it to appear as interlaced? I found this info while searching on Google:

Progressive segmented Frame (PsF, sF, SF) is a scheme designed to acquire, store, modify, and distribute progressive-scan video using interlaced equipment and media.

With PsF, a progressive frame is divided into two segments, with the odd lines in one segment and the even lines in the other segment. Technically, the segments are equivalent to interlaced fields, but unlike native interlaced video, there is no motion between the two fields that make up the video frame: both fields represent the same instant in time. This technique allows for a progressive picture to be processed through the same electronic circuitry that is used to store, process and route interlaced video.

If this is how my clips are supposed to appear in Vegas Pro, should I make any changes to the project settings? I currently use HD 1080-60i (1920x1080, 29.970fps) in all my projects.

Dave


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Dave Osbun
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 8, 2014 at 3:06:13 pm

As a test, I took one of my projects and set the properties to 'progressive' (instead of upper fields first), and played back the timeline. I did not see any difference in the video whatsoever. Set it back to upper field first and again, no difference in playback.

Dave


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Norman Black
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 8, 2014 at 5:04:28 pm

Vegas shows the file as interlaced because that is how it is encoded in the camera output file.

Your camera exposes and captures a full frame, as opposed to exposing and capturing two fields independently, which are interlaced.

The camera output only supports interlaced output because AVCHD 1.0 did not support progressive output in 1080. Only 60i.

Since 60i contains 30 frames per second they worked around this by splitting the full recorded frames into two interlaced fields and outputting that.

The real difference here is that when you deinterlace the file you get a perfect 30p out since that is how the video was recorded. Even in high motion scenes. You should always be able to use the Blend deinterlace mode without artifacts.

A true interlaced recording cannot be perfectly deinterlaced since each field is captured at a different point in time.


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Dave Osbun
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 8, 2014 at 5:34:50 pm

Thanks Norman. I performed a little test by making a new project and importing one clip. I changed the event properties from 'upper field first' to 'progressive', and the project properties were also changed from 'upper field first' to 'progressive'. Upon playback, it looked exactly the same as my normal project (and event) settings.

Is this how it's supposed to work? Should I not bother 'forcing' progressive on each event and just let Vegas use its default settings? I've always had project settings match the video properties.

Dave


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mark thompson
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 9, 2014 at 1:34:51 pm

Hi,
would it be possible for you to post a short clip online somewhere?
It would be interesting to see what the headers are.

thanks
mark


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Dave Osbun
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 9, 2014 at 2:13:26 pm

Here is a Dropbox link to a small clip:
https://www.dropbox.com/s/rikvsqtoizwdaoz/00114.MTS

Thanks!!
Dave


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mark thompson
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 10, 2014 at 6:01:00 am

Hi, thanks very much for the clip.
I put it through Premiere Pro and that also thinks it is interlaced footage. PPro is reported to be abled to auto-detect some forms of PsF
mark


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Howard Steiger
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 9, 2014 at 1:27:17 pm

your shooting with a gh2 right?


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Dave Osbun
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 9, 2014 at 2:01:37 pm

Nope-- i'm shooting with a Sony NEX-VG10. I'll set up a Dropbox account shortly and upload a tiny clip.

Thanks all!
Dave


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Colin Morris
Re: Confusion regarding 30p footage in 60i wrapper (Sony AVCHD clips)
on May 9, 2014 at 5:48:48 pm

Hi Dave,
I use a VG-10 a lot. I bought a very helpful ebook that explains the NEX technical specs really well.
It's called:Shoot great video with Sony Nex cameras by Steve Mullen. Link below.
http://www.mindspring.com/~d-v-c/page10/page10.html

I would highly recommend it.

Colin Mendez Morris
ArsMusica
http://www.arsmusica.ca


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