Mystery of different but the same pixel aspect ratios???

[Rafael Amador]

Hi Matt,
In the end AE and FC can be sure only about the picture size.
Pixels aspect, is to you to tell them, so use the FCs Browser and the “Interpret footage” function in AE.
Cheers,
Rafael

http://www.nagavideo.com

[Matt Carl]

Thanks for your response. If that is the case though why would After Effects be telling me different aspect ratios for FCP clips that used the same exact capture settings? It has always been my impression that AE reads video data (frame rate, size, aspect ratio) the way it was captured to begin with. Is this not correct?

[Rafael Amador]

Hi Matt,
Depending of the codecs, the application can read the meta-data that tell them the real parameters of any footage.
With “modern” codecs you will have less problems with older codecs you will have more.
Most of the time the applications stand for standards: If you ingest a 1920×1080 picture, the applications will set “Square pixels” because that is the standard for any 1920×1080, but you may have built in AE a non standard 1920×1080 with PAL pixels.
If the applications would be able to tell the real specs of the footage, that “Interprete footage” function would be unnecessary, neither you would have the chance to change parameters in the FC Browser.
To know the specs of the clips is a task of the editor and to make sure that the applications understand it, too.
Cheers,
Rafael

http://www.nagavideo.com

[Matt Carl]

Thanks Rafael. That certainly seems to be the case that I need to change the “Interpret Footage” pixel aspect ratio for certain clips so they are not square (1.00). The mystery to me is why AE is reading certain clips as square and others not when they were captured with the same codecs using FCP? Seems like AE can guess correctly on most clips but I don’t understand why it guesses wrong on other clips that seemingly have the exact same properties?

[Zach Cobb]

DVCPro 25 or 50 is 720 x 480, not 720 x 486. Some of the problem could be related to the extra scan lines generated on capture to “pad” the image to 720 X 486.

If you build it, then perhaps you will shut up!

[Matt Carl]

Possibly so but both 720×486 and 720×480 are non square pixel aspect ratios? FCP interprets them correctly but maybe you are correct and somehow something very mysterious is happening within these extra scan lines that causes AE to incorrectly guess the pixel aspect ratio on a few random clips? I wish I could re-digitize these clips at 720×480 to prove this theory but to be honest I can’t figure out how to capture at that frame size through my Kona board? Most likely though there is no rhyme or reason as to why this is happening and I should just accept that like Stonehenge this is purely a mystery that may never be solved.

[John Fishback]

Use a Kona DV or DV50 Easy Setup and you’ll have 720×480.

John

MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.8 QT7.6.4 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24″ TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.1, Motion 4.0.1, Comp 3.5.1, DVDSP 4.2.2, Color 1.5.1)

Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN

[Rafael Amador]

I understand that the footage have been captured as Prores.
(Makes no sense to use a KONA to capture DVCPro as DVCPro: You lose a generation).
You can modify a Capture Preset to get DV 720×486, but not sure if the AJA will take it. Video cards works with standard signals, and a DV 720×486 is not standard.
Neither I think that Matt had modified any Capture Preset.
If you capture by Composite or Components, your DVCPro video is not any more a 720×480 Digital Stream, but a full Broadcast Analog Video that can be captured as 720×480 or 720×486, depending of the codec you want to use.
Rafael

http://www.nagavideo.com

[Matt Carl]

Thanks for the input. I ran a test and recaptured some of the clips at 720×480 (instead of 486) that AE was reading incorrectly as square pixels. Turns out AE read the 720×480 footage just fine (non square) this time. But then to test it further I recaptured this clip a third time using the original 720×486 setting and AE read it correctly for some reason this time as well??? This at least blows the theory that there was some sort of hidden meta data in the original video off the tape telling it to display as square pixel.

Not sure if AE will always read my 480 footage correctly or not now? I plan to test to this more extensively (and will post my findings) but until then it is my theory that the 720×480 vs. 720×486 issue is irrelevant and AE is just behaving quirky by reading random clips incorrectly as non-square pixel even though they have the exact same attributes as other correctly read clips.

[Matt Lyon]

Hi Matt,

You could try downloading the program “metadata hootenany,” which lets you inspect the hidden metadata within quicktime files. (Although a quick glance at an anamorphic file I have here doesn’t turn up any kind of “pixel aspect” flag)

https://www.applesolutions.com/bantha/MH.html

Not sure if it’ll turn up anything useful, but it’s a good tool to have around anyway. I recently had a problem with FCP incorrectly thinking a file was 720×486, even though every other program seemed to think it was 720×480. I edited the “frame” attribute in MH and it fixed the issue.

As for AE, I would chalk it down to quirkiness. I think it’s a good habit, regardless of how well things seem to working, to check that any given program is interpreting your footage correctly (be it Compressor, AE, FCP, etc). Especially before running long render batches!

Matt Lyon
Editor
Toronto