Can anyone explain PsF?

[Geoff Holland]

I wasn't sure where to put this... please move if in the wrong place.

It's to do with how cameras (such as the G10 and XA10) treat video which they say is 30p, but recorded as 60i.... what does that mean, exactly? Why not just call it 60i?

I found an interesting article (part 2of an 8 part series) here:

ProVideo Coalition.com: TecnoTur by Allan Tépper

But it's a bit above my head!!

To a casual videographer, is there anything that should be treated differently when putting our clips together?
Should 30p be avoided?

Thanks.

[Chris Medico]

What it means is that the camera is taking a progressive image (frame) from the sensor but dividing it into into 2 fields. Think of each field as just smaller buckets sitting in a larger bucket (the frame). All the odd numbered lines go into one bucket and all the even numbered lines go into the other bucket. This allows for progressive images to be transmitted using existing interlaced transmission methods.

The difference between PsF and true interlaced is that both fields in PsF represent one moment in time. In contrast with interlaced each field represents a separate moment in time separated by 1/60sec (for i60). This is why when you de-interlace something you may have a quality loss. You are actually combining 2 images that were taken 1/60sec apart in time.

[Geoff Holland]

Many thanks Chris, that's much clearer.

The article was saying there is good PsF and bad PsF.... and the Canon uses "bad". My take on it is that because of this, editing software like Premiere and FCPX treat the incoming info as interlaced (60i) rather than progressive 30, and this can cause problems.

Why would it cause problems and why would Canon just not send it out as 30p, as recorded (the camera must be able to because it does 24p too)?

The article suggests using ClipWrap, but that strikes me as being another time consuming step (and a cost) that I'd rather do without!

I'm recording with 30p, and it doesn't seem to cause any loss of quality because FCPX sees it as 60i.....

[Jeffrey Fuchs]

So what I understand is if you shoot in 24p you are fine. There is only a problem in 30p? If you shoot in 30p the software will see the footage as 60i and adjust accordingly? So if you shooting in 24p or 60i you are fine?

Thanks for posting this.

[Chris Frechette]

There is a problem with all of Canon's PF modes(24,25,30). Some software will do pulldown removal automatically with avchd files from certain cameras(mainly Panasonic). It doesn't seem to work on the PF clips from any of the Canon cameras. When using ExifTool, you can see different Metadata than displayed in the article series linked to by Geoff. It does indeed include data that a software maker could use to detect when pulldown removal should be applied. I have no idea if there are standards for the AVCHD metadata that Canon is not following and if this is the reason manufacturers are ignoring what Canon is including in their files? It seems all the video editing software on the market is not capable of manually applying pulldown removal, which I find just bizarre.

[Robert Young]

RE "good" and "bad" PsF
I believe that "good" PsF is tagged in some manner that allows most NLEs to identify the file as 30 PsF rather than 60i. The NLE will then automatically reassemble the fields into progressive frames and place the footage on a 30p timeline.
The "bad" PsF is identified as 60i by the NLE. In this situation you must use a manual workflow that will reassemble the fields into 30 fps progressive footage.
There is no serious problem with leaving the footage as 60i for editing, mastering, and delivery on an interlaced format like DVD or BR.
The only problem occurs when you need to transcode the 60i PsF to a 30p progressive format.
If the transcoding software/NLE applies a "deinterlacing" algorithm to the file, it will cause an image quality loss.
The trick is to find how to command your NLE to "interpret footage as 30p..." or "conform footage as 30p..." without applying any actual deinterlacing process.

Be cautious about 24p as well.
There are different "flavors" of 24p.
You need to be sure exactly how your particular camera records and outputs 24p in order to understand how to best handle it in post.

[Jeffrey Fuchs]

OK, I am just getting more confused. :)

I use CS5, does anyone know how CS5 and the footage shot with the AX10 at 24P work together? Is there a trick to editing 24P footage from the AX10 in CS5 to get the best results? What is it?

I am about to purchase the AX10 and this may change my decision.

[Chris Frechette]

From what I understand, the XA10 and G10 have both a 24P mode and a PF24 mode. The 24P is actually written as 24P as compared to the PF24 mode which is captured at 24P then has pulldown applied and is written as a 60i file.I don't own either of these cams, so I can't confirm. I'm currently using an HF-M40 which only has the PF24 mode. If you are recording in the 24P mode you should be fine just editing it as 24P.

[Geoff Holland]

Thanks for all the replies.

I'm not really very technical, as I just shoot "home movies" (and the odd "experiment!), but I would like to know that I'm not making my videos worse because of ignorance (although, I know I am!).

I have set FCPX to process the project based on the first clip. I have just looked at one shot in 30p, and it's being handled as 29.97i. That strikes me as being not good. Neither 60i nor 30p.... and I don't have the option to change it.

I also clicked on "show both fields" when a clip was selected in the event browser (unprocessed clips) and the timeline (processed). In the event browser the clip had very broad horizontal lines through it, and although reduced in the timeline, they were still there.

I don't understand why FCPX is seeing 30p > 60i as 30i... I take it this is the bad?

Should I just use 60i or 24p from now on?

Yours, confused. :-)

[Chris Frechette]

If you want to keep it simple, shoot at PF30 and follow part 10 of the guide you linked to in the first post.

[Geoff Holland]

Chris, thanks, I'll review part 10 tomorrow!

You don't say a lot but when you do... it's all worthwhile. :-)

Cheers.

PS.... I've now read Part 10 ( I didn't see more than 8 before!) and it is one of the most useful posts I have ever seen for us Canon users.

Thanks for finding it... I've just got the camera, and just got the software and this is going to stop me making a lot of mistakes.

Thank you again.

[Don Palomaki]

Progressive, especially 24P and 30P, have been the Holy Grail for folks who are trying to obtain that "film look," complete with its motion artifacts and added difficulties with camera moves such as tilts and pans. Use it if you like it.

AVCHD is owned by Sony and Panasaonic. Other manufacturers like Canon need to license the technology. They cannot use the new features, such as 1080P until they can license it. As owners of AVCHD, Sony and Panasonic can (and do) play by slightly different rules. (Note that Panasonic even warned uses that the 1080P mode in ther camcorder such as the TM700 might not be supportd by other gear.)

It may well be that setting the progressive in the file header would have been a violation of the licensed AVCHD specification. AVCHD did not officially support a 1080P mode until July 1, 2011, when it became part of the official specification (V2 Addendum) and available for licensing. This was after the G10 entered the market.

[Geoff Holland]

Don, very interesting and a good explanation. I wonder if Canon will ever release a firmware update?

Having said that, what is the point of 24PF?? 24P is already there, so it can't be a licensing issue....

The more you learn the less you know!

[Don Palomaki]

Progressive segmented frame - Wikipedia, the free encyclopedia.

[Jeffrey Fuchs]

Having said that, what is the point of 24PF?? 24P is already there, so it can't be a licensing issue....

Back to Geoff Question. I hoping "24P" has nothing to do with PsF, can someone with a camera confirm this? This would be a great help. I am planning to buy this camera and use 24P so I would like to know before I buy it.