Pulldown??

[pmk396]

I know that this is such a beginner's question, but what exactly is "pulldown"? I have heard it mention numerous times on the forum regarding when footage is shot in 1080p avchd format. I'm guessing that it is some file conversion process......

Oh, and what are the disadvantages of shooting footage in 1080p avchd format?

 

[swyzlstyx]

http://en.wikipedia.org/wiki/Telecine

Disadvantages of AVCHD? I guess it depends. I can shoot 4 hours of great video on a tiny memory card in my GH1. Being an event videographer, that's pretty cool. You can increase video quality by using less compression (i.e. the hack, or a pro camera), but then you obviously use more recording space. It's a trade off...like most things.

 

[mrmoe]

In short, The GH1 shoots @ 1080p @ 24p (which is wrapped in 29.97). Pulldown on GH1 is when you reverse telecine from 29.97 to 23.976 so you can edit in a 24p timeline (Many use JES or Neoscene for this process). The GH1 Hack allows you to shoot a "Native" 1080p @ 23.976 so you dont need to telecine. Disadvantages of shooting 1080p AVCHD is... a more compressed looking image and you would have a harder time transferring to film.

See swyzlstyx's telecine link @ wiki for details.

 

[alignment1]

mmmm no your all wrong-




:evil:

 

[J Davis]

to quote myself from a post from last year when I was shooting with a gh1

I know there are other threads on this but honestly, I can't make any sense of any of them. I've read that the 1080 video mode is 1080p/24 in a 60i wrapper. Exactly what does that mean? Obviously 60 isn't divisible by 24 so how is this accomplished. And most importantly, is there any software out there for the PC that can extract the 1080p/24 from the 1080/60i wrapper? Should we be able to get to the true 1080/24 data in the AVCHD files? I haven't found any software that can do it.

Thanks,
Mike

It means the sensor delivers information at 24 frames a second, 1920 wide x 1080 high to the chip which then converts this and outputs a stream of the same width and height but it is now interlaced at 60 frames a seconds. Proper terminology for this is 1080p24 from sensor converted to 1080i60 by the chip.
Another part of the chip then encodes the 1080i60 stream into h264 and delivers it to your sdhc card in a form that we know as AVCHD.

Each frame in the 1080i60 stream is really only half a frame because every other row of pixels is missing. (read wikipedia on interlacing). First the odd rows are sent, then in the next frame the even rows are sent. By combining the odds and even rows from the frames you computer will convert the 1080i60 stream into a 1080p30 stream. Now it is 30 full frames a second where every row is represented.

30 frames a second when it was originally 24 frames a second means there is 6 extra frames per second in there. This is called pulldown (see wikipedia on pulldown). You can step through a frame at a time and see the frames that are duplicated. Pulldown removal is the process of detecting the duplicate frames and removing them so you are left with true 24 full frames per second. Corrrectly written as 1080p24.

It actually gets more complex than that when we talk about frame rates 23.976 and 29.97 and 59.94 but I'm trying to keep it a simple and concise explanation for this post.

attached to this dvxuser post is my FCP/compressor pulldown removal settings for gh1
http://www.dvxuser.com/V6/showpost.php?p=1869248&postcount=7


pulldown and interlacing and standard def are all becoming things of the past

 

[swyzlstyx]

.....pulldown and interlacing and standard def are all becoming things of the past

That's what's so crazy about the GH1...Panasonic went BACKWARDS with the GH1. I have their cheap-o SD9 palmcorder I bought years ago...it shoots/records native 1920x1080 24p...requiring no pulldown removal. (I still convert everything to Cineform AVI using Neoscene, so it's no big deal, because editing AVCHD ain't happenin'...even on my quad-core PC. It just takes checking a box to reverse the GH1's pulldown during the process.)

I guess they figured they jumped the gun with native 24p on the SD9, since it's a consumer grade cam like the GH1. Maybe they'll give it another shot with the GH2?

As for standard def...I wish everyone would just chunk all of their old DVD players and buy Blu-Ray players...for no other reason that I hate having to burn both versions every week. Not that I'm such a giant slave to technology (I don't own ANY Hollywood Blu-Ray movies yet), but it wasn't too long ago that I was still having to make VHS wedding video copies for the bride's grandma.