How to Determine if Progressive or Interlaced

[Steve Kalle]

In this video, clip 1 is recorded from the Tricaster XD300's HD-SDI output while an EX3 is playing into the Tricaster at 1080 30p. The nanoFlash was set to 1080 29.97p 100Mb L-GOP.

The Tricaster was set to record the EX3 video which is the clip on the right and is 100Mb/s I-frame MPEG2 420.

The middle clip is the Tricaster playing its recorded video back out via HD-SDI to the nanoFlash with the nano set to 1080 29.97p.

Here is the kicker: the Tricaster only records 1080 60i and someone at Newtek said that it should be outputting 1080 60i. However, the switcher is capable of recording & outputting 720 60p; so, it can handle progressive.

I came up with this idea because I figured the Tricaster could be 'tricked' into thinking the 29.97 PSF feed was interlaced because 60i and 30p 'look' the same over SDI. Doesn't the nanoFlash require manually setting 29.97p recording because it cannot distinguish the difference between 30p & 60i over SDI from an EX3?

Clearly, the switcher's own recording is not as good in the video below. I see quite a bit of aliasing or is that what interlacing does to the video?

So....Are clips 1 & 2 actually Progressive? What happens when interlaced video is fed into the nano while the nano records progressive?
FYI, this video is encoded with H264 at 20Mb/s vbr at 1080 30p.

Tricaster Test 20mb on Vimeo

[Rafael Amador]

Steve,
Whatever is the kind of picture the camera shots (I or P), the Tricaster is getting a 1080i60 stream.
1080p30 is not standard.
If the picture is Interlaced or Progressive, the difference only will be noticed when played.
- If the picture is Progressive, can be played as Progressive or as Interlaced and will always look OK.
- If the picture is Interlaced ONLY can be played as Interlaced: If you play it as Progressive will look WRONG, because you are reading two different pictures at the same time.
Normally you can detect if a movie is P or I on any NLE, but If you want to be 100% sure if a video you need to bring it to an application (AE, SHAKE,..) that lets you step in half frame increments.
rafael

[Dan Keaton]

Originally Posted by Steve Kalle

I came up with this idea because I figured the Tricaster could be 'tricked' into thinking the 29.97 PSF feed was interlaced because 60i and 30p 'look' the same over SDI.

Doesn't the nanoFlash require manually setting 29.97p recording because it cannot distinguish the difference between 30p & 60i over SDI from an EX3?

Yes, to a monitor and to the nanoFlash, PSF is indistinguishable from interlaced (electronically).
1080p29.97, 1080p30 and all other 1080p modes are actually sent as Progressive Segemented Frames, (PSF), which appear to be interlaced (but are not actually interlaced).

What happens when interlaced video is fed into the nano while the nano records progressive?

First, I will describe PSF.

With PSF, the camera uses a progressive sensor and produces a progressive image, line 1, line 2, line 3, follow each other, and all were created at the same instant (well very very close to the same time for some sensors and exactly the same instant for other sensors).

With PSF, the even number lines are split out into one Field of the PSF Frame, with the odd lines put into the other field of the PSF frame.

But, both fields were recorded at the same instant.

If the Vidieo|Record PSF>Prog(ressive) is on, then we take the two fields of the PSF frame and recreate the original progressive frame and then record it.



For interlaced frames, the two fields (even lines in one field, odd lines in the other field) are created from an interlaced sensor, with each field from a different point in time (typically 1/60th of a second (approximately) apart).

If one uses our Vidieo|Record PSF>Prog(ressive) function with interlaced frames, then one gets what appears to be a progessive image, but the even lines were from one point in time and the odd lines from another point in time.

For a static image, this may look fine.

For a moving image, it may not look right.

And to be clear, it will not be correct from a technical point of view
and most likely not from a visual point of view.

[Lance Librandi]

Hello All,
When I purchased my EX3 I did try recording in 1080/25p and could not work out how to stop the studdering effect or flicker especially during zooms or pans. I have recently tried recording in NTSC 1080/30p I was very impressed with the quality of progressive recordings on the Nanoflash the DOF at f5.6 is amazing. I would like to try to find a way to reduce the studdering effect or flicker if anyone can give some suggestions it would be appreciated. I am hoping that with the right camera setting I will be able to use my Nanoflash on progressive to record.

Thanks

[Steve Kalle]

Can anyone explain why the Tricaster clip looks so bad compared to the nanoFlash clips?

[Lance Librandi]

I have been using a bit of detective work with various software to see how they report the clip properties of the Tricaster clip and the give away was that the Tricaster only records in 1080i. Importing the clip into AE and looking at the how AE interprets the clip was the start, it reported clip properties as 1080 30p Separating (Upper). When I import the Nanoflash clip it was interpreted as 1080 30p with no interlacing which can only mean that the clip has told AE that it need to be interlaced output. Then turning off interlacing option off the Tricaster clip in AE the clip played back the same as the Nanoflash clip at 30p. This tells me that the Tricaster can record 30p just one extra step in processing required to turn interlacing off. I am sure there is a technical explanation for all this which I am unaware of but it works. Hey the bright side is the Nanoflash records true 30p and the Tricaster records 30p with interlacing take your pick, 30p interlaced still looks good on my monitor interlaced monitor as well.
This leads me to believe the Triacster XD300 can record 1080 30p inside the 1080i container.

I am truly amazed another format 1080 30pi ? (LOL)

[Rafael Amador]

Lance wrote:
"I have been using a bit of detective work with various software to see how they report the clip properties of the Tricaster clip and the give away was that the Tricaster only records in 1080i. Importing the clip into AE and looking at the how AE interprets the clip was the start, it reported clip properties as 1080 30p Separating (Upper). When I import the Nanoflash clip it was interpreted as 1080 30p with no interlacing which can only mean that the clip ............................
This leads me to believe the Triacster XD300 can record 1080 30p inside the 1080i container.

I am truly amazed another format 1080 30pi ? (LOL)"


Lance , is just the old PSF story.

The Tricaster records only 1080i60, because that is the ONLY 1080 standard on streaming.
That's the way to stream 1080p30.
If you feed him Progressive stuff through SDI, MUST be as PSF, so 1080i60: NEVER 1080p30.

If you want to use AE to see the field order, you must set the composition to step on "0.5" frames increments.
rafael
PS: since last year 1080p60 is a SMPTE standard for 3D.

[Stephen McCarthy]

This is slightly off-topic but not entirely unrelated: I've been doing some work with my nano and an EX-3 running 23.98 "native" and it's been recording nicely and progressively. It seems on the last outing the PSF may have been accidentally activated - possibly when formatting cards in a hurry? - because interlacing seems to have been imposed on the progressive output from the EX-3 midway through an interview. The editor seems to think he can rectify this without too much trouble. Has anyone encountered this phenomenon and, if so, what did you find to be the best way to restore material to it's progressive glory? (The parallel SxS file is intact as native progressive backup.

Cheers,

Stephen McCarthy

[Robin Probyn]

Originally Posted by Lance Librandi

Hello All,
When I purchased my EX3 I did try recording in 1080/25p and could not work out how to stop the studdering effect or flicker especially during zooms or pans. I have recently tried recording in NTSC 1080/30p I was very impressed with the quality of progressive recordings on the Nanoflash the DOF at f5.6 is amazing. I would like to try to find a way to reduce the studdering effect or flicker if anyone can give some suggestions it would be appreciated. I am hoping that with the right camera setting I will be able to use my Nanoflash on progressive to record.

Thanks

Sorry if this is telling granny how to suck eggs.. but.. I shoot alot at 25p with my HDX900 to nano.. almost standard for HD PAL these days.. are you using the camera shutter.. ?? the HDX900 has a 180 degree setting.. ie as with a film camera. Or is your playback system a bit slow for the data?

Otherwise you may have to slow your pans and zooms down abit ?

Again sorry if this is something you know all about already..