Why does 720p record extra frames?

M

mrbrycel

Well-known member
I'm still trying to figure out the difference between 720p and 720pn. I've was searching it all day yesterday, and i'm not sure if what i came up with is correct. Please correct me if i'm wrong. 720p 24p shoots 24 progressive fps, period. 720p 24pn (which is referred to as 720pn at times right?) shoots 60 progressive fps, then in post, automatically removes the 36 extra frames, making it 24 fps. Is that right? If it is, what is the benefit/reason for it to record extra frames?

Also, what 1080pA, and how is it different from 1080p?
 
You have that backwards. 720/24p shoots 60p with a pulldown that is removed in post. 720/24pn shoots exactly 24 frames per second. (The 'n' stands for native.)
1080/24pA is simply a different pulldown from 1080/24p. 24pA records 2:3:3:2, whilst 24p records 2:3.
 
Regarding the "extra frames", it's more the other way around - Panasonic developed a proprietary "native" 24p format that *doesn't* record any extra frames, which exists outside of the standard DV-NTSC format. So it's sort of a Panasonic "rule-breaker" if you will, that allows native 24p recording where other systems simply don't. The main benefit is 2.5 times greater media capacity due to the reduced number of actual frames recorded.

If I have any of this wrong I'm sure I'll be promptly corrected, but that's the basic story as I understand it.
 
The SMPTE-codified transport and broadcast streams for 720p specify 720/60P. The firewire streaming protocol built into Macs and Windows systems specifies 60P. So if you want to broadcast or stream your recording, you need to send a 60p file. So the HVX has the ability to embed its 24P signal within a 60p data stream.

If you're recording onto the cards, there's no reason to bother with all those redundant frames, so they created the 720pN mode for that.
 
I have one more question. When reading up on this before I kept reading that only 720p can go through FireWire. Could I shoot 720pn onto a p2 cards, then transfer the 720pn footage from the P2/hvx200 through FireWire?
 
You can use the PC Connect mode and mount the p2 card on your desktop if you are using Mac using the proper drivers.

Then copy over the p2 volume intact and ingest into FCP.

But you cannot play out FW.
 
Yes. Connect the camera via firewire, put it into IE1394 HOST mode (or is it device mode?) and then the card should show up on the computer. Oh, if you install the drivers for the cards first.
 
mrbrycel said:
I have one more question. When reading up on this before I kept reading that only 720p can go through FireWire.
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Well, not really. Let's say it the other way around: only 720pN cannot go through the firewire. 1080i can, and 1080p can, and 720p can, and 480i and 480p can.

And, let's further clarify: 720pN cannot STREAM through the firewire. But when you've shot footage on the cards and you want to then transfer that footage to a Mac through firewire device mode, yes it can certainly do that.
 
Barry_Green said:
Well, not really. Let's say it the other way around: only 720pN cannot go through the firewire. 1080i can, and 1080p can, and 720p can, and 480i and 480p can.

And, let's further clarify: 720pN cannot STREAM through the firewire. But when you've shot footage on the cards and you want to then transfer that footage to a Mac through firewire device mode, yes it can certainly do that.
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I though that I had this whole 720/24pN thing down before I started reading this thread, but now I'm not 100% sure. If my understanding is correct, then you can not use the Log and Capture feature in Final Cut Pro (FCS2) when using 720pN. I always thought this was possible, but I guess I've never tried it now that I think about it. I guess I've always used 1080i or 720/30p.
Now, does this also mean that you can't live stream out of the firewire port when you're in 720/24pN? I would assume that streaming is streaming, but I want to make sure I have a complete handle on this.

I was hoping to use this mode for an upcoming DVD production of a Willy Porter concert to get a more "film" look, but also for the extended recording time, and I want to make sure I don't run into any road blocks when transferring video to the editing system.
 
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PatrickR said:
Now, does this also mean that you can't live stream out of the firewire port when you're in 720/24pN? I would assume that streaming is streaming, but I want to make sure I have a complete handle on this.
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Correct, the Firewire port is inactive in any PN mode.
 
but also for the extended recording time, and I want to make sure I don't run into any road blocks when transferring video to the editing system.
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I wonder if you have streaming and file transfer confused? The 24pN (and 25pN and 30pN) modes do not, indeed, stream out the firewire port. But if you're just talking about recording to the P2 cards and later transferring to an edit station, yes that will work fine.
 
PatrickR said:
I though that I had this whole 720/24pN thing down before I started reading this thread, but now I'm not 100% sure. If my understanding is correct, then you can not use the Log and Capture feature in Final Cut Pro (FCS2) when using 720pN. I always thought this was possible, but I guess I've never tried it now that I think about it. I guess I've always used 1080i or 720/30p.
Now, does this also mean that you can't live stream out of the firewire port when you're in 720/24pN? I would assume that streaming is streaming, but I want to make sure I have a complete handle on this.

I was hoping to use this mode for an upcoming DVD production of a Willy Porter concert to get a more "film" look, but also for the extended recording time, and I want to make sure I don't run into any road blocks when transferring video to the editing system.
Click to expand...

Now I'm confused. I was under the impression that since the HVX shoots to the P2 cards, log and capture was no longer needed. Doesn't each clip you shot become a file?
 
Every recording becomes one or more files (there is a 4GB file size limit imposed by the FAT32 file system used by the P2 cards).

Unfortunately FCP/FCS doesn't have support for native P2 media and MXF files, so it needs to rewrap everything in a QuickTime container. Depending on what version of FCP/FCS you have, that process is either called "Log and Capture" or "Import P2".
 
The confusion may be coming from the term "Log & Capture." That's not the right term. Log & Capture is for firewire transfer. What FCP uses to import P2 footage is called "Log & Transfer", meaning that it's transferring the footage from the cards to the hard disk.

Regardless of what it's called, FCP's implementation is only one way to go. If you want to work that way, logging your clips and transferring them to quicktime files, then use Log & Transfer. If you don't want to bother with any of that and would rather just immediately edit the camera-original files, look into getting Raylight or MXF4QT.
 
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