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WHAT is Varicam REALLY doing when you shoot 48fps for slo-motion effect?
…and what happens when you do a straight downconvert from the DVCPro HD deck to DVCAM tape? I am told that the downconvert (at a dub house) will be wrong unless you pay for a frame-rate converter. Why? And what does the frame rate converter do?
Now, when you shoot in 24p mode in DVCPro HD and you do a DVCAM down-convert, you get the 24p represented as 24P advanced mode cadence on a 30i tape. You simply remove the advanced cadence fields in Final Cut Pro and edit away in 24p (23.98). That makes sense to me. But. What is the deal when you shoot 48fps for a slow motion effect?
What I would THINK happens is this (but I’m wrong). The DVCPro HD deck plays back at 24p, so you can get a downconvert to DVCAM with the footage represented as 24p Advance mode. Again, you simply remove the advanced cadence and edit away in 24p.
But.
The dub house says they need to go through a frame rate converter first. Why is this? What does the frame rate converter DO? Is it because the DVCPro HD deck plays back at 30p instead of 24p, and thus you don’t have an advanced added in and likewise the slow motion effect is not at slow as it is supposed to be (playing back at 30 instead of the slower 24)? Or What? What’s going on?
Thank you, somebody!
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24 Replies
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[BRussell] “…and what happens when you do a straight downconvert from the DVCPro HD deck to DVCAM tape? I am told that the downconvert (at a dub house) will be wrong unless you pay for a frame-rate converter. Why? And what does the frame rate converter do?”
When you try to convert to slo-mo on the fly during capture or transfer, you will not get all of the footage, you will only get about half of the footage actually transferred that you thought you were getting. It’s much better to pull the footage into a system at 59.94 and then convert it after it’s already in the system.
[BRussell] “s it because the DVCPro HD deck plays back at 30p instead of 24p”
The Deck always plays back at 59.94.
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
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It records 60p at all times.
The lower frame rates are flagged frame.
The frame convertor recognizes the flagged frames and
tosses them. -
Hi, thank you for your help!
So if you don’t play through a hardware frame-rate convertor, then what do you end up with on the DVCAM downconvert?
All 60 frames as all sixty fields, some of those fields repeats because it shot only 48 unique images per 60 frames?
Are the straight DVCAM downconverts (without going through a frame rate coverter) therefore useless for offline editing?
“THE LOST SKELETON OF CADAVRA” –
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Hello, thank you, Walter.
“When you try to convert to slo-mo on the fly during capture or transfer, you will not get all of the footage, you will only get about half of the footage actually transferred that you thought you were getting. It’s much better to pull the footage into a system at 59.94 and then convert it after it’s already in the system.”
Why? What is it doing? Or… Where is the “other half” of the footage going on a straight down-covert to DVCAM tape? Thanks!
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If you desire the actual slo-mo effect then you must use the FRC (which is either the Panasonic hardware device or you can use the plug in for FCP or Avid).
In anycase the dub house is correct.
Obtaining slo mo from Varicam is always a multistep process which must start with the FRC first.
Good luck,
Tony Salgado
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Hi Tony, thank you.
“If you desire the actual slo-mo effect then you must use the FRC … you can use the-plug in for FCP”
You can use the plug-in on media from the DVCAM downconvert? Is that really right?
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Hmm, okay, let me ask it this why then. Why does the a DVCAM Pro HD deck know how to play out for downconvert something recorded at 24p (it simply creates 24pA mode 30i frames), but doesn’t not know how to downconvert for something recorded in 48? Is it because it just blindly transfers each HD frame to an SD field regardless of what rate it recorded at?
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[BRussell] “You can use the plug-in on media from the DVCAM downconvert? Is that really right?”
No, you cannot. Only works on DVCPRO HD footage.
For you to get slow motion, you have to have it dubbed at the post house to DVCAM that way. But then you run into the issue it it not matching back properly to the master tape, which ISN”T slow motion. Best to take the 48fps footage, have that dubbed to another DVCPRO HD tape as slow motion, then THAT is the new master and you get that one dubbed.
But really..this is SO complex a workflow. Simply capturing DVCPRO HD via firewire or with a capture card and working with it that way (the format really isn’t all that demanding. Firewire 800 drives handle this. But a decent eSATA Raid will be not too expensive, and handle this well.
KISS – Keep it simple, stupid. Not that you are stupid…that ‘s just how the saying goes.
Shane
Littlefrog Post
http://www.lfhd.net -
Because, BRrussel, when you shoot 24p on a varicam, that is essentially a ‘normal’ or real time frame rate for playback. If you shoot 24p, that means you want 24 frames a second which is easily extracted and added to a 60i tape with pulldown at a real time frame rate. Now, when you have 48 frames per second which is an offspeed format used for slowmotion effects and not a normal playback speed, it makes it much harder to get 48 frames of video in to a 30 frame stream. Really what you are doing with the slow motion footage it taking those 48 frames and playing them back @ 24 frames (essentially doubling the real time playback which can’t be done on a real time down-covert, except with specialized hardware such as the FRC). Since panasonic decks don’t have an FRC built in you must first extract those 48 frames from the 60p cadence by the methods that people have told you. If you have a Kona card, you can use that as a hardware FRC by the way, with caveats that have already been mentioned. You then plop those 48 frames in a 23.98 sequence (again, essentially playing these at half their normal ‘shot’ speed) and then lay that off to dv tape, down converted with pulldown. Does that make sense to you?
Why do you need to do DVCam down-converts? Perhaps we ca hash out a better workflow for you without all this trouble. DVCPro HD is workable using a reasonably fast, but not top of the line laptop and cheap storage.
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Thank you, Shane, that really helps. Am I understanding correctly then that DVCPro HD only and always downconverts one HD frame (60th) down to two SD fields? If so, then I understand all this.
Yeah, client is offline editing using DVCAM, and I will be onlining from the HD masters. I would love it if offline matched.
One last question based on your advice. 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?
Sorry about all these questions — I’ve never worked with this vari HD format before.
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