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Old August 7th, 2009, 12:55 AM   #1
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One last thing on psf

Ok guys. Sorry for all the questions. I read the FAQ and then I read the FAQ again. I'm still not clear if psf is retained on footage recorded to the XDR/Nano. I see it says in the FAQ that pulldown is not removed but psf is not technically "pulldown" exactly.

So I ask the question here for clarification. If my camera outputs psf, does the XDR/Nano write real progressive frames or does it write psf like my camera outputs.

Well, I should say one of my cameras outputs real progressive frames (this is nice), but the other camera outputs psf and this is the one that worries me.

If psf fixing is lumped in with pulldown removal, I guess the good news is that it will eventually be added as a feature. Just looking for a little clarifcation ...

Thanks, Aaron
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Old August 7th, 2009, 07:39 AM   #2
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Dear Aaron,

Yes, we support PSF (Progressive Segmented Frames).

Many cameras' HD-SDI output is PSF when you select a progressive frame rate on the camera such as 23.976, 23.98, 24, 29.97 or 30 progressive frames per second. This allows a non-progressive monitor to display your images.

In PSF, the original progressive frame is divided into two fields, one for even lines, one for odd numbered lines. Then the monitor gets this and either puts it back together and shows one progressive frame or displays it as two fields. Early monitors used the second option.

The Flash XDR and nanoFlash handle PSF. We have a menu option which you can select if your input is PSF.

We take the two fields, process it, and recreate the original progressive frame, then we record it (full progressive).
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Old August 7th, 2009, 08:52 AM   #3
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This is excellent news! Maybe another line should be added to the FAQ.
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Old September 3rd, 2009, 10:43 AM   #4
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Dan,

I may be a little confused here about psf. I thought I understood it, but maybe not so much. I would appreciate some input and correction, if appropriate.

My two Panasonic HDX900s are the primary cameras with which my nano is going to be used. Of course, I may be renting the nano to other shooters occasionally, so I need to understand the psf function as fully as possible, too.

My understanding of the HDX900 is this. The camera is switchable between 720p and 1080i, but it always records true progressive frames (not psf), because it uses a progressive imager (720p), which is always progressive. It has no way to produce a real interlaced image. When shooting in 1080i, it is actually producing and recording two identical progressive fields, as opposed to an odd and an even field, which would be typical of an interlace imager. When playing back, it also plays those two identical fields. This is the case whether the frame rate is 60i, 24p, 25p or 30p. (Note that the Panasonic tape-based cameras always record 60 frames, no matter what frame rate is selected. Extra frames for 24, 25 or 30 frame recordings are flagged when recorded and not shown during playback.)

Now, if my understanding of that is correct, that makes it different from the Sony F-900 and F-900R, because those cameras use interlace imagers. Those cameras natively record an interlaced image, so they must use psf to record a "progressive" image.

So, I have three questions about this.
  • Am I understanding these concepts correctly?
  • Should I be using the "psf in" function when recording the output of the HDX900? I would assume the answer to be "no" for that camera whether I am shooting 720p or 1080i, since the camera doesn't actually ever produce a real interlaced image. (This assumes I am understanding the HDX900's recording and HD-SDI output correctly.)
  • Should I be using the "psf in" function when recording the output of a Sony F900 or F900R. I would assume the answer to be "no" if I am shooting 60i. I would assume the answer to be "yes" if I am shooting 24p, 25p or 30p, which would be psf on those cameras (always interlaced).
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Old September 3rd, 2009, 11:40 AM   #5
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Quote:
Originally Posted by Steve Brown View Post
Dan,

Now, if my understanding of that is correct, that makes it different from the Sony F-900 and F-900R, because those cameras use interlace imagers. Those cameras natively record an interlaced image, so they must use psf to record a "progressive" image.
Steve, this is a tough subject.

As I understand it, PSF is a way to take a progressive image, and make it "psuedo interlaced" so that an interlaced HD-SDI monitor can display it.

If all of the HD-SDI monitors that were ever made supported true progressive frames, then PSF would not be needed or used (in my opinion).

PSF works by taking a progressive frame, and placing every other row into two fields.

Then, if the receiver, such as the nanoFlash or Flash XDR, knows that it is PSF, then the two fields are processed to rebuild (and record) the true progressive frame.

Thus, with PSF In Checked, if one provides us with PSF, then we rebuild the original progressive frame.

Now, certain cameras have interlaced sensors, but are able to create a progressive frame.
Normal interlaced images have a time delay between the two fields.

If one has a camera that has interlaced sensors, but builds progressive frames, then two fields can be read out so that a progressive frame can be created.

Canon does with very well with their XL H1 24F and 30F modes. I am assuming that Sony does the same thing, but I do not have this level of information.



Quote:
So, I have three questions about this.
  • Am I understanding these concepts correctly?
  • Should I be using the "psf in" function when recording the output of the HDX900? I would assume the answer to be "no" for that camera whether I am shooting 720p or 1080i, since the camera doesn't actually ever produce a real interlaced image. (This assumes I am understanding the HDX900's recording and HD-SDI output correctly.)
  • Should I be using the "psf in" function when recording the output of a Sony F900 or F900R. I would assume the answer to be "no" if I am shooting 60i. I would assume the answer to be "yes" if I am shooting 24p, 25p or 30p, which would be psf on those cameras (always interlaced).
One should never check the PSF In, if you are providing the nanoFlash a 1080i signal.
For 720p it is not necessary to check the PSF In.

For 24P, we are able to set the PSF In option internally. So one does not need to worry about PSF if your footage is 24p.

For 25P and 30P we need to know and the PSF In must be set accordingly.
If you camera's specs say PSF, please check the PSF In option.

If you get this wrong, then a quick check of the footage visually will show problems. It just will not look right, it may look interlaced.

Steve, I hope this helps.

I also welcome comments and suggestions. Maybe someone can explain this better than I, or correct me if I made a mistake.
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Old September 3rd, 2009, 02:00 PM   #6
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As I understand it within the specifications for SMPTE 292 HDSDi there is no provision for 1920x1080 progressive signals. As a result any progressive 1920x1080 images must be encoded as PsF in an interlace stream. So if you are working with a 1080P camcorder the HDSDi will be PsF. There is no loss of quality or motion issues when using PsF, in most cases it's use is completely transparent.
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Old September 3rd, 2009, 02:12 PM   #7
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Dear Alister,

You said it better than I could.

In my opinion, if the PSF In option is set correctly, then

1. A progressive image in the camera is converted to two fields (PSF).

2. The PSF is sent out via HD-SDI.

3. The receiver, such as the nanoFlash, converts the two fields (PSF) back to progressive.

Nothing is lost in this process.
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Old September 4th, 2009, 01:12 PM   #8
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Thanks guys. This is very helpful info and furthers my understanding of this technology. I will re-set the nano for "psf in" and check the output and files!
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Old September 6th, 2009, 03:00 PM   #9
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The biggest difference between psf and standard interlaced is that the two fields from psf, taken from a progessive sensor, are captured at the same precise instant in time. There are no interlacing artifacts at all.
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Old September 11th, 2009, 07:04 AM   #10
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Quote:
Originally Posted by Alister Chapman View Post
As I understand it within the specifications for SMPTE 292 HDSDi there is no provision for 1920x1080 progressive signals. As a result any progressive 1920x1080 images must be encoded as PsF in an interlace stream. So if you are working with a 1080P camcorder the HDSDi will be PsF. There is no loss of quality or motion issues when using PsF, in most cases it's use is completely transparent.
Then, just to clarify for my sometimes-dense mind, I should set PSF In to the ON selection when recording 1080/24p or 1080/30p from Sony EX1/3

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Old September 11th, 2009, 07:24 AM   #11
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Dear Ned,

Yes. But I will verify this for you this morning.
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Old September 11th, 2009, 07:43 AM   #12
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The NanoFlash will work with PsF ticked or not. Sony's (and most other) cameras when set to progressive output a PsF signal which to the NanoFlash is no different to an interlace signal.

The NanoFlash does not know whether what it is seeing is Progressive or Interlace. If you tick the "PsF In" box the NanoFlash records the input as progressive. The biggest potential problem is if you are shooting interlace and you leave the box ticked as the interlace footage would be recorded as progressive. If you dropped interlaced material recorded as progressive into an interlace timeline it may not be displayed correctly.

In short if you are shooting Progressive you need to tick the box, if you are shooting interlace, no tick.

If you are at all unsure the safest is to not tick the box. Any progressive PsF material would be recorded as Interlace by the NanoFlash, but this shouldn't really make any difference when the files get played back, but it may confuse you as your files will report being interlace while the content is progressive.

I hope that makes sense.
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Old September 11th, 2009, 08:10 AM   #13
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Dear Alister,

Thanks for the assistance.
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Old September 11th, 2009, 08:33 AM   #14
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That makes ample sense. I appreciate the clarity of the response!

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Old September 14th, 2009, 06:44 PM   #15
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Ditto... thanks to everyone for the clarifications!
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