NEX-5N's Progressive Segmente Frame is the "malignant" kind

Started Nov 24, 2011 | Discussions thread
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feijai Regular Member • Posts: 210
NEX-5N's Progressive Segmente Frame is the "malignant" kind

We all know that the "60i" in the NEX-5N is actually 30p broken down into interlaced fields through a technique called "Progressive Segmented Frame" (PsF). What you probably didn't know is that it appears that Sony may have blown it.

Apparently some manufacturers who generate PsF create a version which is immediately recognized as progressive when loaded into an editor. Several others make broken versions of PsF which are recognized only as interlaced video. This broken version is termed "malignant PsF".

The above URL uses a piece of Mac software called VideoSpec to highlight malignant versus benign PsF. I've downloaded the same software and sure enough: according to this definition, the NEX is producing malignant PsF.

The problem: when you load benign PsF into Final Cut Pro X, it recognizes it as progressive. When you load the NEX's "malignant" PsF video into Final Cut Pro X, it treats it as interlaced . You can include it in a progressive project, but this may involve transcoding it to progressive, and if FCPX doesn't know better, this could significantly impact on the video quality. I don't know if it does or not -- FCPX is pretty opaque about its transcoding procedure. And you absolutely want a progressive project (FCPX will by default make it interlaced!) because otherwise the video comes out awful.

Furthermore, if you just rewrap the raw 60i Sony videos into Quicktime using MediaConverter, and display with Quicktime Player, they come out as interlaced and with some pretty awful interlacing artifacts.

So far the only way I've been able to eliminate those artifacts is to load the files into FCPX, stick them in a progressive project, and then output the project. This is a problem because, without Compressor, FCPX outputs to HD video at only about 15MBps. It's also a problem because FCPX doesn't say what kind of interlacing conversion it performs to convert the interlaced Sony videos into progressive format. It could be just re-weaving the two fields (which would be awesome) but it could also be stuff like deinterlacing or decombing filters, which would not be a good situation.


1. Does anyone know what FCPX actually does to the Sony NEX-5N's PsF video when converting it to a progressive project? Does it run it through a deinterlacing filter?

2. Does anyone know of any simple, free OS X tool which can convert Progressive Segmented Frame video into proper Progressive video without doing lossy deinterlacing? I mean, how hard can this be to re-weave the two fields?

3. Does anyone know why Sony has "malignant" PsF in the first place?

I think Sony may have screwed the pooch on this one.

Sony Alpha NEX-5N
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