Is 1080p Possible with D800 HDMI Output ?

Started Mar 17, 2012 | Discussions thread
Brad Morris
Veteran MemberPosts: 4,442
Like?
Re: recovering from 3:2 pulldown
In reply to bob elkind, Mar 25, 2012

bob elkind wrote:

Brad Morris wrote:

[dangling sentence fragment] pull down, when the interlaced components of each frame are replicas of each means that you loose nothing during the conversion other. If you save a broadcast 1080i stream from your cable TV or Free to air broadcast, you will get losses during the conversion because all the data is not contained in each half if the frame signal

I've been involved with the television industry for almost 20 years, and I don't understand this explanation. I must be getting old...

Pulldown is a conversion process between progressive video and interlaced video.

If you want to understand 2:2 and 3:2 pulldown, read the Wikipedia article for "Telecine". There are a number of SMPTE signal standards for embedding data or markers which enable reverse pulldown conversion (i.e. from interlaced back to progressive format). Unfortunately, HDMI does not support such signal standards, and this is why 3:2 pulldown is considered a "lossy" conversion in the context of HDMI-connected equipment.

Sony has implemented a non-standard set of pulldown flags for HDMI-cabled gear, but this is worthless if the receiving gear doesn't understand the proprietary Sony signal protocol. HDMI video recorders such as the Ninja do not record (preserve) the Sony signals, so the special Sony signals are not available to video processing gear on the output side of (for example) the Ninja recorder.

Simple 2:2 pulldown can be readily reversed without data loss from the original progressive format signal source. The problem case is 24p video converted to 60i. In this case, 3:2 pulldown is used, whereby 5 video frames are generated from 4 source frames. Two of the five output frames contain video material from two different source frames. Without knowing which frames are "clean" and which are combined, the 5 output frames cannot be separated back into 4 frames.

The nasty part is that 3:2 pulldown creates noticeable motion artifacts. A smooth motion in the source video will appear to stutter in the output video, because some source frames are used in one output frame and some source frames are used in 1-1/2 output frames.

So...

3:2 pulldown is lossy.
3:2 pulldown introduces visiible artifacts.
3:2 pulldown is not reversible, without help.

in the recorded 24p footage recorded over HDMI out, field 1, and field 2 and field 3 in each frame are identical images. the key is to tell your editing software not to de interlace the file.

I found this in a vimeo discussion that talks about usage of hdmi out on the ninja recorded footage in Final Cut Pro 7.

"Ninja records progressive in interlaced mode or progressive segmented (PsF). For 25 p this is simple, all you have to do inside Final Cut Pro is change the field property of all imported clips from odd to none.

I you fail to doing that, Final Cut Pro sees your footage as interlaced even though it is not and it will apply desinterlacing automatically and will therefore lower the quality of the footage by adding artifacts.

I asked Atomos support whether they could get the files to be flagged as progressive while recording in an upcoming firmware update, but it apparently is not possible.

So if you work 25p or 30p from the original interlaced flagged ProRes just make sure to always do that "

And this is why the output signal format on the D4 and D800 HDMI port is important. Fortunately, Nikon seems to have 'done the right thing' in both the D4 and D800, so that interlaced output video -- and 3:2 pulldown -- is avoidable.

-- hide signature --

Bob Elkind

Family, mostly sports. Seriously, folks, I'm not that good. If I can do it, you can do it!
photo galleries at http://eteam.zenfolio.com
my relationship with my camera is strictly photonic

-- hide signature --
Reply   Reply with quote   Complain
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow