Major Aliasing Problem

[John DuMontelle]

<shaking my head> Don't understand the angst some are displaying about learning the ins and outs of 30P from someone who really knows what he's talking about.

I am by no means at the freelance level of Doug Jensen but, like him, I rarely shoot anything that isn't 30P anymore. Have yet another 30P shoot this Friday where they specifically asked for it.

Many of the network news magazine shows want 30P. Have you folks watched PBS, 60 Minutes or the CBS Sunday Morning News lately? That's pretty much all they want. At least that's what they asked for from me. Granted, there's 60i video mixed in but for the elements I've been involved with shooting them, it's been 30P

I saw the link from the company labeling a format 1080I 30...seems strange but I'm no engineer, just a guy who gives the client what they ask for so they give me a check in return.

There's a lot of misinformation in this thread and it's NOT coming from Doug Jensen.

I'm not trying to begin a flame war of who is and isn't professional.

Just pointing out I'm yet another freelancer with real world clients who want 30P more and more.

We're not talking about taking a raw feed out of the camera directly to whatever monitor or tv set you happen to own. We're talking about an image which is edited, then broadcast to achieve the look they want. If it was a problem, they wouldn't be coming back again and again for more.

edit: I want to be very clear that I am not trying to insult or demean anyone with my above comments. Just trying to share some information. ;)

[Eric Olson]

Originally Posted by John DuMontelle

Many of the network news magazine shows want 30P. Have you folks watched PBS, 60 Minutes or the CBS Sunday Morning News lately? That's pretty much all they want. At least that's what they asked for from me. Granted, there's 60i video mixed in but for the elements I've been involved with shooting them, it's been 30P

While 1080p30 is part of the ATSC broadcast standard, I don't think it is actually used because of the desire to mix in 1080i. Many HDTVs will accept a 1080p signal, but blu-ray doesn't provide a 30p standard. In both cases 1080p is often processed as 1080i. If a 1080p image is of sufficiently high resolution, then processing it as 1080i will result in aliasing. As shown in the original post, the EX3 produces such images. In this case, the workflow needs to be fixed so the frames are processed progressively throughout.

Are the files recorded by the nanoflash tagged as interlaced or progressive?

[John DuMontelle]

Hi Eric,

Looking at video information and....not sure where to find an answer to your question.

Here's the info I have for my latest 30P shoot I did for PBS network of the raw BPAV files.

Video Format

Port: DIRECT
Codec: MPEG2 HDLong 35bps
FPS - Capture: 29.97P Format: 29.97P
Layout: 1920 X 1080 16:9
Pull-Down - Type: 1-1 Frame Phase: 00

That's the video information I get seeing the files in my XDCAM Browser.

So...would the double "0" for Frame Phase provide the answer? I'm not sure...just asking.

[Eric Olson]

Originally Posted by John DuMontelle

Port: DIRECT
Codec: MPEG2 HDLong 35bps
FPS - Capture: 29.97P Format: 29.97P
Layout: 1920 X 1080 16:9
Pull-Down - Type: 1-1 Frame Phase: 00

This appears to be a correctly tagged 1080p progressive 35mbps file. Is there aliasing with this one too? I thought the aliasing was only a problem with the 50mbps file recorded by the nanoflash.

[John DuMontelle]

No, I've never had aliasing problems...we just got caught up in a discussion about the positives and negatives of 30P and that took everything off track.

My video is perfect!

Of course! LOL ;)

[Dana Kupper]

Originally Posted by Steve Kalle

Hey Doug,

I appreciate the comments so far, but I know of one reputable company who refers to 1080 30i instead of 1080 60i - Aja. Actually, they list it as "1080i 30". KONA LHi - AJA Video Systems

I do believe the 1080i 30 is correct because the '30' refers to the number of frames per second. 1080 60i is incorrect because it is not 60 frames per second, but 30 fps. All of the 'Video Formats' include the frame size and frame rate, not fields per second; thus, 1080i 30 is correct, and so is 1080i 25.

I was confused by this as well, but I think I figured it out.
My question was how can it be both 1080i and 30p? I believe the difference is in how the image is captured and then recorded.
The picture is captured as progressive, in other words, all pixels at once. It is recorded as interlace, the picture is spilt AFTER capture, and therefore there are no 'interlace artifacts' as we think of them.
I like to think of it as two different 'flavors' of interlace, ha ha!

Can anyone confirm/debunk this explanation?

[Eric Olson]

Originally Posted by Dana Kupper

My question was how can it be both 1080i and 30p?

A video can't be 30p and 1080i at the same time.

Processing a progressive frame as two interlaced fields is the probable cause of the aliasing observed in the first post. Luckily the nanoflash records with 4:2:2 chroma subsampling, otherwise there would be additional chroma artifacts from using the interlaced 4:2:0 algorithm on a progressive 4:2:0 frame.

[David Heath]

Originally Posted by Doug Jensen

This is really getting ridiculous. 30i is not a real frame rate and does not exist. Please show me one legitimate industry source that recognizes 30i as a real frame rate. If it was a real frame rate, 30i would only be 15 fps. Just as 60i is only 30 fps.

Let's clear this up.

Up until a few years ago, the correct nomenclature for what you are both referring to would have been "1080/60i" (30 frames, 60 fields), and for the comparable progressive system it would have been "1080/30p".

The relevant standard setting bodeis then decided it would be better (and don't shoot me, I'm just the messenger only.... :-) ) to ALWAYS refer to framerates, and NOT framerate when progressive, fieldrate when interlaced. To avoid confusion (!!!!!!!!) it was further defined to change the way it was written, such that i or p before the hyphen indicated new (and official) nomenclature.

Consequently 1080/60i should now be referred to as 1080i/30. Both mean the same thing - but the former is strictly "old" terminology.

Earlier Steve Kalle said "I appreciate the comments so far, but I know of one reputable company who refers to 1080 30i instead of 1080 60i - Aja. Actually, they list it as "1080i 30".

And the point is that 1080/30i and 1080i/30 DO NOT mean the same thing. The former means an interlaced system of 15fps framerate, using old terminology! The latter is the correct way of referring to one of the main current broadcast standards. At least according to the bodies responsible for standard setting.

GRADUALLY the new terminology is replacing the old, and arguably is more logical. Given the confusion it has caused (and still is causing) it could be argued forever whether the change was worth it. I'm not going to get hung up on that, but officially 1080i/30 is the correct terminology.

[David Heath]

Originally Posted by Dana Kupper

The picture is captured as progressive, in other words, all pixels at once. It is recorded as interlace, the picture is spilt AFTER capture, and therefore there are no 'interlace artifacts' as we think of them.
I like to think of it as two different 'flavors' of interlace, ha ha!

Can anyone confirm/debunk this explanation?

Following on from my previous post, what you describe is correctly referred to as "1080psf/30". "psf" stands for "progressive, segmented frame" and is exactly what you refer to. (Google psf if you want more details.)

[Steve Kalle]

Originally Posted by David Heath

Up until a few years ago, the correct nomenclature for what you are both referring to would have been "1080/60i" (30 frames, 60 fields)...

GRADUALLY the new terminology is replacing the old, and arguably is more logical. Given the confusion it has caused (and still is causing) it could be argued forever whether the change was worth it. I'm not going to get hung up on that, but officially 1080i/30 is the correct terminology.

I would posit that a reason for changing to 1080i 30 is due to 1080p 60 becoming more relevant and referring to 1080 60i AND 1080 60p *could* be rather confusing. For most of us, its not confusing but think of all of the consumer handycams that now include both 60i and 60p recording modes.

[David Heath]

What I understood to be the reasons were more academic - that sometimes referring to framerate (progressive and psf) and sometimes fieldrate (interlace) was illogical. If framerate is ALWAYS specified it becomes more consistent and it's possible to tell at a glance the raw data rate from the two figures, (So 1080i/30, 1080p/30 and 1080psf/30 will all have the same aount of uncompressed data - 1080p/60 will be double.)

I agree with the logic - but the question of whether the confusion the change has caused was worth it (witness this thread) is another one. I'm not going to go into that, the main point is that, officially, 1080i/30 is now the correct terminology.

[Dag Halvorsen]

[QUOTE=Steve Kalle;1721934]Has anyone seen this level of aliasing from their EX1/3/1r? I have never seen aliasing this bad with either my EX3 or EX1.....

If I have the same problem or not, I'm not sure, but here's my situation:
I'm shooting with EX1 at 1080p/25 (PAL region). In Vegas, the project setting is 25fps and progressive. However, in the preview windows, it says 50i. Why?
When I render to an m2ts file plus ac3 audio file, and pack them together to an iso file in DVD architect and play it on an LCD HDTV, severe aliasing appears: A black wire against a grey sky background appears with white lines on both sides of the black wire; all crispy dark details have white glare around them; contrast seems exaggerated, TV set says "1080i" is playing (from media player, not blu-ray player).
What happens? When in the workflow did it all shift from progressive to interlaced?
When I play back the same m2ts file on my computer, everything is normal (!!)...

PLEASE help... ;)

[Steve Kalle]

Hi Dag,

Your aliasing problem is most likely due to the scaling algorithm being applied by the DVD player to scale the resolution up to your HDTV. This aliasing issue varies between every DVD player because they all use various scaling algorithms with some being worse than others. The best way to combat this issue is to apply anti-aliasing effects in your NLE (if it has them - Premiere Pro has an anit-flicker setting and an anti-alias effect which essentially applies a slight blur but I think it focuses more on high frequency).

From my experience, very slight aliasing in the source footage can show up as ugly aliasing in a DVD on an HDTV due to the DVD player's up-scaling.

[Eric Olson]

Originally Posted by Dag Halvorsen

TV set says "1080i" is playing (from media player, not blu-ray player).

Are you rendering a blu-ray iso? How does it look when you play the files extracted from the iso on the computer? What type of media player are you using?

[Dag Halvorsen]

Originally Posted by Eric Olson

Are you rendering a blu-ray iso? How does it look when you play the files extracted from the iso on the computer? What type of media player are you using?

Preparing a blu-ray iso in Architect, yes. No re-rendering required in architect.
I'm using the QNAP NMP1000 media player.
QNAP Systems, Inc. ( NMP-1000 ) - Quality Network Appliance Provider
It's not fast enough to play iso-files, so I put the iso file on a virtual drive, and copy the BDROM catalog onto the QNAP, which plays it well.

Actually, I experience the same aliasing problems playing the m2ts file in windows media player, output via HDMI to a HDTV set. On the PC monitor however, it looks good. Weird...

The footage is native 1080p/25 from the XDCAM EX1, so why it appears as 50i in Vegas when playing it from the timeline, is also a mystery. Also, when the rendered file is opened in DVD architect, the file appears as 25i, even though I've selected "Maintain source file format"... Even more weird...