Question about converting to ProRes in FCP

P

ProAmateur

Active member
So I have a question...

I have read and read and read to try to understand the concepts of 1080p vs 1080i vs 720p and on and on. For me and my HMC150, I am mostly shooting run and gun fast action motor sports. And based on much of what I read here (including from Barry, for whom I have much respect) it seems a sweet spot for the HMC150 is 720 60p...at least for lots of fast action motion.

So now I am looking for a B cam. And since its a B cam, I have been looking at the high end consumer Canon and the 300 series panny. But, from what I can read, none of these shot 60p at all. Seems as though 60i is the commonplace.

So my question...does it really make a difference in my situation? I am using FCP and ingesting as ProRes. And here is what is confusing me. I am not really sure what happens when I do that. Obviously there is a difference between 60i and 60p, but does that difference become a moot point when you convert to ProRes?

I guess what it comes down to is that I am looking for a B cam, and instead of coming out and just asking what you guys think, I am trying to analyze the various factors and come up with an answer on my own.

Regards,

G.
Student

P.S. Someone on here once wrote in their sig line "Friends don't let friends shoot interlaced." It stuck with me. Hence my questions about 60i.
 
I know that signature, too - I've been telling my friends about it :).

The problem with interlacing is that to make it go away, you effectively have to cut your vertical resolution in half.

I won't go on much about interlacing as I only understand it at a superficial level, but I will say for a B-cam that if you can wait until fall, keep your eyes out for the HMC-40. It'll do 720/60p, shoot on the same SD cards that work in the HMC150, and it should have a familiar layout to boot.
 
I've been successfully converting 1080/60i to 720/60p using Compressor. Of course it won't look as good as shooting 60p natively and sometimes the deinterlacer causes artifacts in the image depending which algorithm is used.
 
Well it makes me wonder...unless forced to by the limitation of the camera (ie won't shoot progessive), why would anyone ever shoot interlaced?

To be honest, I wish it were just easier to understand. I mean I "think" I get 60i and 60p, but then they throw in 24p over 60i and 30p over 60i, and then this "wrapped" in that. My goodness.

Regards,

G.
Frustrated
 
Honestly... before I got into video I always assumed all video whether it was online, on television, at the movies, whatever.. was just a bunch of frames playing one after the other. Now that I've gotten into this stuff.. there are so many weird technicalities going on inside of the video it seems that it confuses the crapola out of me.
 
Well can someone explain to me the meaning of what read on page 108 of the HMC150 manual?

Looking only at the PH mode, it lists 1080/30p and 720/30p but both listed as "over 60i" and both in the 30p column. What is "over 60i"? And for that matter, what does it mean in the 24p column when it says "native recording"? I just ask about the native recording thing because I am trying to understand the significance of that versus where is says nothing at all (like in the 60 column).

Regards,

G.
 
Over 60i means that telecine or 3/2 pulldown is done making the footage is now 60i (i.e. interlaced). You must do an inverse telecine to get your progressive frames.

Native recording means that only 24 progressive frames are recorded. No telecine is used.
 
ProAmateur said:
Well it makes me wonder...unless forced to by the limitation of the camera (ie won't shoot progessive), why would anyone ever shoot interlaced?

To be honest, I wish it were just easier to understand. I mean I "think" I get 60i and 60p, but then they throw in 24p over 60i and 30p over 60i, and then this "wrapped" in that. My goodness.

Regards,

G.
Frustrated
Click to expand...

I remember being just as confused as you guys when I first got into video. 60i/60p was the hardest thing to grasp, and I found, since I am a visual person, that it wasn't until somebody explained it to me in pictures that I fully understood it.

Like TigerFX said, essentially, when you deinterlace, you are cutting your vertical resolution in half. This is because you take each an odd field and an even field per frame of interlaced footage and stitch them together, but basically you lose half the detail per frame because at any given moment in time, only half the picture was recorded. If you don't get this, don't bother.... let me explain with diagrams...

To first understand what "30p over 60i" or "24p wrapped in 60i" is, you must think about a digital camera on two levels.

  • Recording at the chip - I won't go into detail, but first you must realize that the chip/sensor records the picture as digital "bits" or data by sensing the different colors of light that come through the lens. At any given point in time (or rather 1/24th of a second with 24 fps, or 1/30th of a second at a frame rate of 30) the sensor captures a still image full of the different colors of light and sends it over to the processor to be processed. It is here that the image information gets turned into digital "bits" as I just mentioned. Once that is saved it sends it over to the storage medium...
  • Recording to the storage device/tape - This is where the "wrapping" comes in... The second level of recording that happens on most prosumer-level cameras is that once the image has been turned into "data" it then needs to be stored somewhere for later retrieval. The camera will take each frame of RAW data and then play it BACK to another recorder/sensor that re-records the same frame you just shot (we are slowing down time to nanoseconds here) to a new timeline, this time having the frames interlaced and split into fields. Essentially, what this does, is make the large RAW data very small once it is finally saved on the memory card/tape. The end result however, is an interlaced piece of footage, but the look or the actual FRAME RATE is in 24p or whatever frame rate you shot in because that is what the original image was captured at.

This process is happening at lighting fast speeds and takes place 24 times in a second if you are shooting at 24 fps. Another way to think of the two levels is first the camera goes through the ACQUISITION STAGE and then to the MASTERING STAGE.

Although your footage LOOKS like what was captured at the acquisition stage, the footage you will be editing will be whatever it was saved/recorded to at the mastering stage. This is what "24p over 60i" is.

So where were the diagrams in all of that? Here... let me show you the difference between an interlaced timeline and a progressive timeline. For simplicity's sake, we will look at a "30p" timeline and a "60i" timeline. One quick thing that is probably the MOST CONFUSING thing to understand, is that 24p, 30p, and 60i are just nicknames to distinguish the different types of footage we work with. Really what they mean are:

  • 24p = video shot at a true frame rate of 23.976 frames per second, progressively (meaning each frame is completely captured and saved in its entirety).
  • 30p = video shot at a true frame rate of 29.976 frames per second, progressively (meaning each frame is completely captured and saved in its entirety).
  • 60i = video shot at a true frame rate of 29.976, but has each frame split into an ODD FIELD and an EVEN FIELD. This is called interlacing. The "60" part actually stands for 60 fields, NOT frames, unlike the other two above.

    This is the deceiving difference between 30p and 60i. Essentially both share the same frame rate, just progressive refers to complete frames and interlaced refers to the number of fields.

And now finally, if you are lost, let's look at the diagrams. Please take a careful note at the syntax to this logic:

Code: 
{ } = anything between these is a complete frame.
A, B, C, D = delineates one frame from another in the sequence
1, 2 = delineates between ODD and EVEN fields within an interlaced frame
| = a matching pair of fields that fit together into their respective frame (or "letter")
... = the pattern repeats and continues

Assuming a 24p timeline:
Code: 
{A}  {B}  {C}  {D} ...

Assuming a 60i timeline:
Code: 
{A1|A2}  {B1|B2}  {C1|C2}  {D1|D2} ...

Assuming a 24p over 60i timeline with 3:2 pulldown (telecine):
Code: 
progressive frames:  {A}  {B}  {C}  {D}

odd fields:  {A1}  {B1B1}  {C1}  {D1}  

even fields:  {A2}  {B2}  {C2}  {D2D2}

complete pulldown:  {A1|A2}  {B1|B2}  {B1C2}  {C1D2}  {D1|D2} ...  
(notice the 3:2 ratio: 3 perfectly matching frames, then 2 that are mixed.)

Man that took a while, but I hope it helps. If people find this helpful maybe I should make it into it's own thread and sticky it. We'll see.

NOTE: The way I explained the levels of camera up above is just a conceptual theory to explain a simple idea of how to think of it. It's not exact or accurate by any means in terms of an actual definition of how a digital camera works. Think of it more as a simplified model.
 
WOW, that was very helpful to me. In fact, I printed that off to put in a file for future reference. Thanks for taking the time.

Regards,

G.
 
I shoot 720 60p on my 150 as my main cam for weddings, and I use a Canon HF11 cam as my wide locked-down shot. I transcode both to ProRes and drop the 720 60p footage in the timeline first to establish that as the sequence settings. Then I'll drop the 1080 30p footage from the consumer HF cam in. I rarely use slo-mo with the wide shot, so it doesn't matter much that it is 30p. It works and it's cheaper than buying a full priced pro cam.

As soon as I can afford a GH1 I may very well start using that as my main cam and the 150 as my wide cam. That way I can use 720 60p for both angles.

Jack
 
ProAmateur said:
WOW, that was very helpful to me. In fact, I printed that off to put in a file for future reference. Thanks for taking the time.

Regards,

G.
Click to expand...

Glad to hear it ProAmateur. Maybe we could sticky it? I find 24p/30p/60i is one of the hardest things to grasp when new editors/filmmakers are just starting out. :)
 
You must log in or register to reply here.
Back
Top