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24p Jitters
I’m currently loading HDCAM tapes shot on a Sony CineAlta900 at 1080p-23.976 for a Documentary project. I’m working at low-rez (14:1) on Avid Media Composer on a 23.976 project and capturing via MoJo-SDI. I’m seeing a lot of stuttering – especially when there’s a lot of camera movement. I know there’s some of this to be expected but I want to be sure I’m not doing something wrong that will cause problems down the road.
Ronnie
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6 Replies
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Sounds like your cadence is messed up.
Are you starting all of your clips with Timecodes that end in zero or five?
For example 1:00:00:00 is good
For example 1:00:00:01 is bad
For example 1:00:00:05 is good
Only zero or five is correct for the A frame (assuming you are coming from the HD deck and not some downconvert which may be screwed up)
If this is what is happening, and I’ll bet it is, then let me know and I can explain what you are seeing.
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
Thanks Terence,
That’s what I suspected so I started capturing this way and it does seem to make a difference however I do think the media is being down converted because even though it’s coming from an HD deck, it’s going through a Mojo SDI port.
Furthermore, (and maybe this is normal) my clips are being logged at 29.98 fps, not 23.976. Will this cause problems when I am ready to uprez?
This is my understanding of shooting at 24 fps… The camera pulls down to 30 fps (because that’s the time base of ALL video) and when you import into Avid, you remove that pull-down. Is that correct?
Ronnie
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[Veronica Rutledge] “Furthermore, (and maybe this is normal) my clips are being logged at 29.98 fps, not 23.976. Will this cause problems when I am ready to uprez? “
No, it’s the same thing. Folks just round up to 23.98 as it’s easier to say than 23.976. Even 23.976 is rounding as I believe the equation goes a lot further.
[Veronica Rutledge] “This is my understanding of shooting at 24 fps… The camera pulls down to 30 fps (because that’s the time base of ALL video) and when you import into Avid, you remove that pull-down. Is that correct? “
Yes, basically. The HD deck adds 2:3 pulldown to the downconvert. There is no 23.98 SD tape format, so it is assumed that you always want 29.97 (29.976 to be precise, and see, here they rounded down, don’t you love standards).
When you capture into an Avid 23.98 SD project, it removes the extra fields based on a standard 2:3 pulldown added with the A (or first frame in a pulldown sequence) being a zero or five.
To see this graphically illustrated, check out:
https://www.zerocut.com/tech/pulldown.html
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
[Terence Curren] When you capture into an Avid 23.98 SD project, it removes the extra fields based on a standard 2:3 pulldown added with the A (or first frame in a pulldown sequence) being a zero or five.
This part still confuses me- when the 2:3 pulldown is applied upon import into Avid, should it read at the same frame rate of the project? Because my footage is being captured at a frame rate of 29.976.
Ronnie
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[Veronica Rutledge] “This part still confuses me- when the 2:3 pulldown is applied upon import into Avid, should it read at the same frame rate of the project? Because my footage is being captured at a frame rate of 29.976”
If you are in a 23.98 project, your footage is being captured at 23.98. If you want to see it in action, capture a window burn. Now step through frame by frame and you will find 6 of the 30 frame numbers missing.
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
Thanks for clearing that up Terence!
Ronnie
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