AVC Intra, 1080/24p over 60i, 24pA, and 2:3:3:2?

S

Soundfx4

Active member
Greetings Dvxuser forum, I was advised to visit this forum for my not very strait forward question that I posted in the avsforum. It was suggested that I ask my question here, and I was even given a link directly to this section of the forum! I did do a bit of searching before posting this but as it's not a very strait forward question (and considering that I'm quite tired atm) it was difficult to find any posts that answered my question. On top of all that, I'm incredibly happy to of found this place because I'll be renting this very camera for a local production within the next couple of months and I need all the resources I can get to ensure that when I get the camera I have a good idea how to work with it right off :) Okay on to the question :D

I've been looking into Digital Cinematography video camera's lately and after deciding that my first choice for a digital format would be HDCAM SR I quickly found my initial thoughts to be correct; that any HDCAM SR camera is completely out of any possible budget I will ever have. I took a liking to AVC Intra however and ended up finding the Panasonic HPX300 and found several things that I liked. First and foremost that the image sensor is 1920 x 1080 and records with a pixel aspect ratio of 1:1 not a freaking 1440 x 1080 image sensor with a 1.33:1 aspect ratio which many cameras and all HDV camers do. It also tells me that it records in 1080/24p but this is where I get confused. I started reading the brochure to make sure that it didn't do anything I wasn't going to like and in the list of recording modes under 1080/24p it says the following:

"The 1080 and 480 progressive recording systems convert recordings to 60i
in 24p, 30p, or 24pA (Advance) mode. The 24p Advance mode uses 2:3:3:2
pulldown, which allows for an easy extraction to a 24p timeline and no
quality loss in the process with compatible NLEs."

Confused, I googled 24p over 60i and found one relevant result at the creative cow forum. In fact it was a forum post asking exactly what I was asking, but the answer was less than helpful and possibly confused me even more. So I looked up 2:3:3:2 pull down at wikipedia and now (you guessed it) I'm even more confused! hehe

Basically what I'm understanding is that it stores it in 60i on the camera and then does a 2:3:3:2 pulldown for editing? This makes no sense to me; why can't they just store it in 1080/24p? I want a system that Captures in 1080/24p, processes in 1080/24p and STORES it in 1080/24p. What possible reasoning could there be for throwing Interlaced crap in there anywhere? I honestly don't understand it, which is why I'm asking, but at the same time I'm flat out @$#%@# to see that stupid freaking "i" at all! I hate interlaced footage with a passion, especially since there is no need for it anymore....bah, but I have a feeling that I'm not understanding what it means at all, which is why I'm hoping someone here can possibly explain it too me :)


Here is a link to the instruction manual and the brochure; in the manual search for "Standard and Native Recording" This answered some questions, but brought up many more. For starters, it doesn't seam to show an example of 2:3:3:2 pull-down. To add to that, it even seams to show native recordings being converted to interlaced footage and then back to progressive footage before being recorded? Why would it need to do that? Also, I'm not sure, but it looks to me like the manual and brochure are contradicting each other. The brochure says 24p must be done over 60i (as stated above) but the manual says there is a 24pN. /shrug

AG-HPX300 Instruction Manual

AG-HPX300 Brochure

Thanks much!
 
If you are shooting in an of the modes that has a "p" you will be shooting in progressive and not interlaced. Don't worry there.

The reason for the pull down is that when recording on tape, the tape runs a a consistent speed and needs to record 60 things per second. No matter what. thats a tape thing. So they developed the pulldown for 24p footage it records certain frames twice in a mathematical formula that the NLE can then remove the extra frames and knows which ones to remove.

When we moved to tapeless there was a need for people to record in the same manner as other footage the recoded on tape, thus the reason for having this format still exist in a tapeless world.

It sounds like what you need is a"native" format. anything with a "n" at the end. For example 24pn will record 24 frames per second, progressive natively. The native means it does not record the extra frames that then need to be removed by the NLE. there are also 30pn formats as well as native formats for other .
 
AVC-Intra 50 and 100 is a Native, Progressive codec with no need to be compatible with legacy tape formats. What is recorded on P2 cards is Native and Progressive. What is output via HD SDI is over 60P for 720 and 60i for 1080. This is because of display compatibility and compatibility with the two official HD formats, 720/60P, 1080/60i. 24P and 30P are output over 60P or 60i for the HD SDI outputs.

With tape based formats, there is no Native recording, therefore all frame rates have to be recorded over 720/60P or 1080/60i with post-production pull-down.

AVC-Intra, besides being Native, Progressive, is full sample square pixels, 10-bit color depth, which has 4X more shades of gray vs. 8-bit, 4:2:2 color space in the case of Intra 100 and I-Frame frame structure. To be able to get this codec quality at the price-point of an HPX300 is unprecedented. Sony protects its higher end cameras by only allowing 35Mbps bit rate, 8-bit, 4:2:0 and Long GOP frame structure with its sub-$30k cameras.
 
Simple answer: if you're using AVC-Intra, there is no pulldown, it's native 24p exactly like you'd expect.

Pulldown only comes into play with the other recording formats (DVCPRO-HD 1080, DV/DVCPRO/DVCPRO50 480).
 
Beautiful! Wonderful! I've no need to worry then :) I'll admit I'm still a little confused, but my biggest concern was addressed and I feel much better now.

I would, however, like to try and understand this somewhat better; The camera's "system" mode for 1080/24/30pn is 1080/60i? So is that why it says in the manual that for native recording that the "camera recording" is in 24pn, but then it performs a 2:3 pull-down so that it can be output via 1080/60i but then the actual "Recording" uses only the "active" frames from that signal to give you 24pn in the video data? Am I on the right track somewhat?
:dankk2:
 
That refers to the signal it sends out (over component, etc.) to display the footage on a TV screen or monitor.
 
David Jimerson said:
That refers to the signal it sends out (over component, etc.) to display the footage on a TV screen or monitor.
Click to expand...

souka...so it has to do a 2:3 pull down to what the camera captures so that you can view what the camera sees on an external display (if you choose to use an external display). But that doesn't effect what's actually recorded onto the P2 card! I think I got it now :)
 
Yes, you've got it.

It's imaged as 24fps.
It's recorded as 24fps.

For compatibility with monitors, it's converted to 60i (using 2:3 pulldown) when displaying it. But the recorded footage is native 24p.
 
Barry_Green said:
Yes, you've got it.

It's imaged as 24fps.
It's recorded as 24fps.

For compatibility with monitors, it's converted to 60i (using 2:3 pulldown) when displaying it. But the recorded footage is native 24p.
Click to expand...

:bath: Excellent! Very relieving to have a better understanding of this; thank you for verifying that I'm on track now, and thank you all again for the replies!
 
AVC-intra50 / 60i vs AVC-intra50 / 30PN

AVC-intra50 / 60i vs AVC-intra50 / 30PN

Please help me understand something?
We are moving to HD and London has decided we (NYC) go with:

SYSTEM MODE: 1080-59.94i
REC FORMAT: AVC-intra50 / 60i

We will be recording on P2 HPX250EJ and ingesting directly to NLE (Avid)

......what is the differences between AVC-intra50 / 60i AND AVC-intra50 / 30PN ??

I've noticed at least one full stop of difference between the two and I'm thinking the 30PN will
be more efficient for ingesting and editing... but I really don't have any clue !

Please, any info you can offer to help me better understand this strange new world of HD.



Dino said:
AVC-Intra 50 and 100 is a Native, Progressive codec with no need to be compatible with legacy tape formats. What is recorded on P2 cards is Native and Progressive. What is output via HD SDI is over 60P for 720 and 60i for 1080. This is because of display compatibility and compatibility with the two official HD formats, 720/60P, 1080/60i. 24P and 30P are output over 60P or 60i for the HD SDI outputs.

With tape based formats, there is no Native recording, therefore all frame rates have to be recorded over 720/60P or 1080/60i with post-production pull-down.

AVC-Intra, besides being Native, Progressive, is full sample square pixels, 10-bit color depth, which has 4X more shades of gray vs. 8-bit, 4:2:2 color space in the case of Intra 100 and I-Frame frame structure. To be able to get this codec quality at the price-point of an HPX300 is unprecedented. Sony protects its higher end cameras by only allowing 35Mbps bit rate, 8-bit, 4:2:0 and Long GOP frame structure with its sub-$30k cameras.
Click to expand...
 
If they set it to 1080-59.94i and AVC-Intra50 at 60i, then that means you will be recording 1080/60i footage, an HDTV standard. It will be interlaced, and the motion will look like "real life".

If you set it to AVCI50/30pN, then that means you will be recording 30 progressive frames per second. It will look more filmlike, and will not be interlaced. It won't look like "real life", it'll be a bit more surreal, more filmlike, with stuttery motion on wide pans and such.

If your head office has declared to go with 60i, then I would go with 60i...
 
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