Need help understanding frame rates/drop frame

[Chet Kenisell]

Hello,

On page 48 of the user manual, there are the following recording modes:

• AVCHD 28 Mbps LPCM (59.94P)
• AVCHD 28 Mbps (59.94P)
• AVCHD 24 Mbps LPCM
• AVCHD 24 Mbps
• AVCHD 17 Mbps
• AVCHD 5 Mbps
• MP4 35 Mbps (59.94P)
• MP4 24 Mbps
• MP4 17 Mbps
• MP4 4 Mbps
• MP4 3 Mbps

But on the on page 50, there are the following frame rates:

• AVCHD 59.94I - 59.94 fields per second, interlaced.
• AVCHD PF29.97P - 29.97 frames per second, progressive (Recorded as 59.94i).
• AVCHD PF23.98P - 23.98 frames per second, progressive.
• MP4 - 29.97P - 29.97 frames per second, progressive.
• MP4 - 23.98P - 23.98 frames per second, progressive.

I understand that the list of frame rates on page 50 do not include 59.94P because it is set by default when choosing the AVCHD 28 Mbps LPCM (59.94P), AVCHD 28 Mbps (59.94P) or MP4 35 Mbps (59.94P) recording modes.


This is what I'm not understanding:

If these are Progressive video frames, why is it "59.94P" instead of "60P"? For example, film is usually shot at 24fps. So, that would be 24P. Not 23.97P.

Of course, we're not shooting film here and this is completely digital, so I am assuming that, in order to conform to NTSC standards, the time code is performing drop-frame and this is why the label is "59.94", "29.9" and "23.98".

So is the XA20/XA25 really recording 60 full progressive frames when set to 59.94P? Is it recording at 30 and 24 full progressive frames per second when set to 29.97P and 23.98P respectively?

[Chet Kenisell]

Part 2 of my question will affect post production (so I need to make sure I understand what's going on before beginning):

ALL of my footage for this project has been shot in AVCHD 28 Mbps LPCM (59.94P).

To edit this in Premiere Pro CC, which project preset should I use? Should I simply create my sequences from the video assets? Would this ensure that the Premiere editing would be performed in AVCHD at 59.94P?

Finally, I will be encoding the Premiere sequences into a Blu-ray compatible format. Since 59.94P isn't officially supported by Blu-ray at 1920x1080, should I export to 23.976P?

I am really trying to maintain the absolute BEST picture quality possible throughout post-production all the way to watching the final product on a Blu-ray player at home.

Thanks!

[Steve Bleasdale]

Maybe don't look at the 59.94 and 23.97 and 29.97, look at them as 60p 24p 30p that's the USA, in England we are 25p 50p. If you want 50i interlaced use 59.94 interlaced I.
Whatever you choose use the pre-set in prem pro dslr 24p 30p or 60p or avchd the same. I find filming 50p and pre-set down to 25p don't feel good so pre-set the same as filmed.
Also if you film 60p use a 120 shutter speed. 30p 60 shutter speed, 24p 50 shutter speed. They say double the frame rate for shutter speed is always best but? Steve

[Don Palomaki]

30 frames/60 fields per second was the original USA B&W TV (at power line frequency for technical reasons of the time).

Because of the way color was implemented, and to retain compatability with B&W sets, they had to shift the frame/field rate slightly to avoid interference artifacts among the TV signals internal components (e.g., line scan rate, vertical refresh rate, color carrier), thus the slight shift to 29.97/59.94. This is close enopgh to 30/60 for B&W sets to work while avoiding the interference issues. (Remember, all this was done in the 1950s with analog circuits adn signals, not digital.)

Drop frame was a way to count frames in the color signal while staying within a frame or so of the real time clock. Important for broadcast timing, less so for home video.

[Chet Kenisell]

Alright, so just to confirm...

59.94P is really 60 full frames per second.
29.97P is really 30 full frames per second.
23.97P is really 24 full frames per second.

The drop-frame is simply time-code that is independent of the actual frame rate.

I will create my sequences in PP CC using the actual 59.94P AVCHD source footage so that I can maintain the original frames/encode without having to transcode.

Now, how should I export my Premiere Pro CC sequences in order to be Blu-Ray compatible (using Adobe Encore to author my dual-layer Blu-Rays)?

Thanks again!

[Steve Bleasdale]

Yes spot on.. good luck