-
WHAT is Varicam REALLY doing when you shoot 48fps for slo-motion effect?
-
Hi, thank you, Jeremy.
To answer your questions, this client’s documentary was edited all this past year as offline using DVCAM downconverts of HD tapes. They recently did these many varicam pick-up effects shots and have consulted me, so we are trying to figure out how to get them downconverts that match the HD masters… that I actually will be onlining myself at another facility. I’ve never worked with DVCPro HD before so it is all confusing to me. Sigh.
What I think I understand is two things now: 1. DVCPro HD always downconverts one HD frame to one SD field. 2. When you capture in final cut you specify the frame rate you shot at (or otherwise it detects the frame “flags”), and all the other duplicate frames that make the remainder of 60 are thrown away… so if you say you shot at 48, FCP FRC gives you a 48fps clip running at a 48fps normal speed (by discarding 12 redundant frames). I got that right? Then you manually create the motion effect in 24p by slowing down the footage.
-
[BRussell] “If one captures said DVCPro footage in FCP, one captures specifying 48fps and then later slows it in the sequence to 24 for the motion effect?”
Correct. OR, if you are shooting with the HVX-200, you can have the camera slow the footage down when it records it, so you import it at 24fps, but it is the 48fps, frame for frame transfered and thus slow motion. If it is on tape, then you capture it at 48fps (in a 59.94 stream) and using the FRC, transfer those 48 frames…frame by frame…into a 23.98 clip.
[BRussell] “Am I understanding correctly then that DVCPro HD only and always downconverts one HD frame (60th) down to two SD fields?”
I believe so. I haven’t ever done a downconvert, so I can’t really say for sure.
Shane
Littlefrog Post
http://www.lfhd.net -
Thank you, Shane!
-
[BRussell] “They recently did these many varicam pick-up effects shots and have consulted me, so we are trying to figure out how to get them downconverts that match the HD masters”
That will be tough with offspeed material.
[BRussell] “When you capture in final cut you specify the frame rate you shot at (or otherwise it detects the frame “flags”), and all the other duplicate frames that make the remainder of 60 are thrown away… so if you say you shot at 48, FCP FRC gives you a 48fps clip running at a 48fps normal speed (by discarding 12 redundant frames). I got that right? Then you manually create the motion effect in 24p by slowing down the footage.
“No, you don’t need to manually slow down the footage. This is the point of shooting offspeed so you don’t have to slow down the footage. What happens is this. You are editing in a 23.98 timeline. You then capture your off speed footage @ 59.94. Within the 60p stream there a 12 frames that are flagged. You open the FRC, tell it what you want to do such as what frame rate to conform to (23.98 in this case), if you want to make make the movie self contained, and other options. Then the FRC removes the flagged frames, and then sets the tc rate of the clip (23.98). It then takes those 48 frames and spreads it out to 23.98 frames per second and makes a new clip, so your clip is now two seconds long instead of the one second you originally captured and it’s running @ 23.98 fps instead of 60 (or 48). Make sense?
Jeremy
-
It does make sense, thank you. The FRC is a feature that appears when capturing DVCPro 100 footage… or is FRC only a feature of FCP 6?
-
No…it is something you do AFTER you capture.
Here..I have a tutorial…
https://library.creativecow.net/articles/ross_shane/dvpro_hd.php
Shane
Littlefrog Post
http://www.lfhd.net -
I’m sorry to be such a dunce… I get it now thank you, third party tool and should work with any version FCP HD. But the converter in the tutorial only works with 60fps… what of 48?
That tutorial was awesome, btw, very cool.
-
(I mean, does it automatically recognize the flagged frames and call it 48 instead of 60?. Anyway, okay nevermind, I guess if it throws away duplicate frames, then you end up with 48fps before it finishes processing to 24. No more bothering y’all then, I REALLY appreciate the time you’ve taken to answer this!)
-
[BRussell] “Why? What is it doing? Or… Where is the “other half” of the footage going on a straight down-covert to DVCAM tape? Thanks!”
The deck cannot do the slo mo by itself during a downconvert. You would need to run through a hardware frame converter or through a Kona box to slo mo in realtime during a downconvert.
But during this process, the tape deck is still running at 59.94. You’re extracting the 48fps in realtime. So you’re extracting slow motion footage.
Let’s say you have 1 minute clip you want to slow mo so you set up a realtime downconvert to capture that 1 minute in slow mo. What will happen in reality is that 1 minute shot will lengthen to about 1.5 – 2 minutes depending on the frame rate you shot at. Well tape decks work in timecode, not slow mo. So you capture that 1 minute with the deck running at 59.94 but you’re converting it to 48fps for slo mo on the fly. You only end up with about 30-45 seconds of actual slow mo footage because the deck stops in exactly 1 minute based on timecode. 1 minutes of 59.94 will equal about 30-45 seconds of finished slo mo footage if converting in realtime.
It’s incredibly confusing and you don’t really understand it fully until you do your first realtime downconvert. After we tried it once in realtime, we never did it again, just started using the Frame Rate Converter in FCP.
FYI, we have a full Varicam forum here on the Cow.
Walter Biscardi, Jr.
https://www.biscardicreative.com
HD Editorial & Animation for Broadcast and independent productions.All Things Apple Podcast! https://cowcast.creativecow.net/all_things_apple/index.html
Read my blog! https://blogs.creativecow.net/WalterBiscardi
-
Hi,
I was involved in the very early days for Vari-Cam and shot my first feature film on it. We were only using it for it’s ability to shoot 24fps and didn’t use it for slo-mo.
We ran into horrendous problems with frame rate convertion, when we down shifted from HD to DigiBeta. This was because the very early Varicams had a glitch in the software which flagged the frames and this resulted in the timecode becoming separated from the frames during the conversion.
Basically, when we came to online we had to adjust every single clip by hand, as they were anything between four frames and two seconds out of sync.
The good news is that this glitch was sorted very early on and frame rate conversion is a fairly painless problem these days.
I’m a big fan of the Varicam, it’s a good system, but I think the thing I learned on that outing is that it pays not to be one of the first people to use a new system. Almost all of the workflow problems I’ve encountered over the years of pioneering HD and HDV have occurred when people have been using the very latest equipment.
Varicam has been around long enough now for the workflows to be well understood and stable.
Reply to this Discussion! Login or Sign Up