Capturing Raw (4:4:4) Mini DV footage directly to a harddrive.

Hey guys. I'm getting ready to shoot a frew greenscreen shots for my film, and I've been wondering if anyone has ever tried to capture Mini DV straight from the camcoder while recording directly to a hard drive so that you get a full 4:4:4 signal instead of 4:1:1. I have all the proper equipment to do it with, I just need to know if it's possible.

 

No, because MiniDV records at 4:1:1, not 4:4:4. The compression happens in the camera as it is recording to the tape. It's the nature of the signal, and even recording directly from the camera to a hard drive won't change it.

I'd like nothing more than to be proven wrong, because this would make bluescreening for my own film much less nightmarish, but I don't think I'm wrong.

M. Scott

 

There IS a way:

On some cameras, the video out signal (not the firewire, but the composite/svideo outs) is not compressed unless you're playing back from tape (the XL series is like this). You'd need to run the composite outs to a analogue capture card on a FAST machine with FAST hard drives, and capture uncompressed YUV or Huffman compressed YUV (since HurrYUV is lossless). This means you'd have to have a desktop on set.

Two other considerations:
1) You'll want as little overhead on the capture box as possible. This means running in console/command prompt mode on your box if you can. If not, run your windowing system (linux/windows/mac) as lean as possible, close down EVERYTHING that runs except your capture program, and capture to a disk that does NOT have swap or system files on it. Otherwise you'll drop frames as your memory fills up.

(2) Actually, I lied - only 1 other consideration
-Lokmer

 

i believe this is possible. simply plug your firewire into your computer while shooting and capture the live feed. Never touching the tape, so maybe it is not compressed since it is basiclly going throught the CCD's then the circutry then straight out the firewire.

I think i am going to try this. Capture the footage live, then capture the footage that was recorded and see if i can tell a difference.


later guys

 

Dorkman: You just might be right. Also, Dorkman, don't you know GREEN is much better than BLUE when doing Mini DV?

Brent: When you try this out, there is a DEFINATE way to see if the signal captured is 4:4:4 or 4:1:1. Take a STILL of the video into Photoshop. Convert it from RGB mode to Lab mode. Then open up the channels window and click the A or B channels. Check them both. If the edges seem blocky, then it's 4:1:1, if it's not block, then you did indeed capture a 4:4:4 image.

 

kool, as soon as i get home and get some time i will try it.

 

don't you know GREEN is much better than BLUE when doing Mini DV?

Of course. That's one of the first things you learn around TFN. But one of my characters has a green costume and that's just the way things go.

M. Scott

 

Sorry guys. The nature of DV makes it impossible to do any of the above. If you hook up the analog ( s- video or composite) output of the DV camera and capture through a hardware capture card ( with an array fast enough), all you basically are doing is DOWN converting the digital signal to an analog signal. You cannot bypass the nature of 4:1:1 compression when dealing with miniDV which has a fixed rate of 3.6 mb/sec. You will probably be able to pull better keys off the footage captured from the analog source though the capture card, but the quality will lose a 1/2 generation.

 

DarthMoves: So you are saying that the video signal is compressed to 4:1:1 before it is split to go to the Tape Deck and the ieee port?

Or is it more like being hooked up in series...like it goes from CCD's to Deck to ieee?

 

<<Also, Dorkman, don't you know GREEN is much better than BLUE when doing Mini DV?>>

I can't believe people discuss this kinda crap. I'm fed up of it.

This is an AMATEUR board. If your keying isn't very good or you're not happy with it, then get someone better to do it or put up with it!

yes, people will bitch about it, yes people will pick up on it, but who gives a damn? I'd rather watch a film with a plot and dodgy keying than a film without a plot and near perfect human CG (Final Fantasy is an example of great graphics with no storyline).

anyway,

Nick "Shorty" Long

 

Wasn't Duality shot on blue...?

 

yes it was.

 

Speaking of great FX and no plot...

-Paul

 

What you are suggesting isn't really possible. The compression of dv cannot in any way be avoided when using minidv cameras. The information is stored on the miniDV tapes in 0's and 1's, so the compression happens immediately. The transfer rate of dv is 3.6mb/sec and that is non negotiable. If you capture it at a higher setting ( via hardware) you lose quality because it is not a lossless transfer.

 

The only way this would EVER be possible is IF - and only if - the camera outputs the raw CCD info into the ANALOG OUTPUT while you are recording.

My guess is that most cameras are lazy and don't do that, since there would need to be some specialized circuitry for this, when it would be much easier to have the circuitry work like this

CCD -> DV ENCODER -> TAPE/RECORDING MECHANISM -> DV DECODER -> ANALOG OUT

So even if you do get stuff out "live" via the analog out it's fairly certain that it has already been under DV compression.


A few facts some people misunderstood:

1. There is no such thing as "uncompressed DV", (people get this idea from the fact that if you ONLY EDIT in premiere, the data is not RE-compressed, meaning PURE CUT edits is actually digital copies of the input, bit identical. ANY edit, even audio change, causes a recompress)

2. There is NO WAY to get "uncompressed" data over firewire because firewire transfers the COMPRESSED DV data stream always

3. There is no way to find "uncompressed" data on the tape because DV compresses the data GOING TO THE TAPE

4. The only place in the camera where there exists uncompressed RGB data is in the buffer after the CCD just prior to the DV compressor circuit. You need to be able to "tap it off" THERE somehow, to get at it.


All this said, some people claim you get better keys by going analog! However, most these people dont understand that all they are really doing is a chroma blur. You can do chroma blur in AE too (or use a blurred version of your footage to pull the matte and apply the matte to a sharp version, or blur your matte, or...etc)


I just want to kill the myth of "uncompressed DV" because it doesn't exist, DV *is* a compression scheme.

/Z

 

It is now when you start to see why expensive formats like Beta and digibeta still exist.

DV is good for prosumer, but if you are dealing with any sort of pro level delivery, no one is taking dv seriously yet. I work for a major commercial production company and when we get dv masters, we send them back and request beta sp masters and digi beta masters. We even work with 3/4 u-matic before dv.

 

That is why whenever I get a DV tape from a client i capture it and then convert it to uncompressed (or i use the huffy codec, which is lossless). That way there is only 1 generational loss. From then on i edit all uncompressed untill it is time to export.

 

<<DV is good for prosumer, but if you are dealing with any sort of pro level delivery, no one is taking dv seriously yet.>>

I beg to differ. The BBC and Sky take DV very seriously. Local news programs use footage shot on MiniDV cameras (admittedly it's high end such as the PD150 and XL-1S) by their videojournalists. Certain TV series' are shot on DV ("Streetmate" springs to mind) as well as documentaries.

<<I work for a major commercial production company and when we get dv masters, we send them back and request beta sp masters>>

Why? DV is better than SP anyday.

<<and digi beta masters.>>

Which costs a bomb

<<We even work with 3/4 u-matic >>

I'm amazed at how many commerical companies still do when DV is so much cheaper, and probably better quality

<<before dv.>>

how very arogant!

We did a test with a mjor TV channel (without them knowing about it in fact) when we made a series for them.

We shot one week with DVCam, the other with DigiBeta. We then edited a show with both sets of shots and charged them with the task to get their technical/quality department to pick out the DV shots.

They pegged a couple of shots as being "soft" (i.e. out of focus). They were DigiBeta shots that were (in fact) shot that way. The cameraman hasn't worked for us again!

anyway,

Nick "Bet no-one could guess the DV from the Digi shots" Long

 

Hey Nick,

I was just stating how the business works. Those U-matics STINK, but there is such a reluctance to embrace something new. In my experience, MiniDV is not too popular. DVCPRO has a place. BTW, you get a better chrominance with Beta SP than with DV. DV does yield more lines of resolution, but at 1/2 the color sampling. I personally think you get better picture with DV, but that's just me.

Mike

 

don't you know GREEN is much better than BLUE when doing Mini DV?

Of course. That's one of the first things you learn around TFN.

For some reason this exchange strikes me as incredibly funny, and I don't know why.

But I can see a grizzled old poster taking a newbie aside and saying, "Now, son, you listen good. Don't spam, read the FAQ first, and remember that green keys easier than blue when shooting on MiniDV..."

Heh. I dunno.

(I also don't know what the first filmmaking things I learned from this forum WERE, but I don't think it was about blue vs. greenscreen.)

Anyway, carry on.



Rick McCallum loves you!

 

I work at a post facility that accepts all kinds of formats.

One of our Edit suites is a Discreet smoke* which works in full 10-bit uncompressed format hooked up via SDI to a Sony DigiBeta deck.

If you showed me DV then DigiBeta and it was viewed on our professional monitor I could definitely tell which was which.

Most of the commercials we shoot are all done on 35mm film then transferred to DigiBeta. Sometimes the budget is small and they use DV.

After working there for 2 years my eyes have become finely tuned to look for the devil in the details. And now because of it, I feel my GL1 is almost inadequate LOL

 

<<Hey Nick,

I was just stating how the business works. Those U-matics STINK,>>

yes they do!

<<but there is such a reluctance to embrace something new. In my experience, MiniDV is not too popular. >>

I guess the UK is accepting it a bit more than the USA

<<DVCPRO has a place. >>

DVCPRO is actually that little bit worse than DVCAM, DVCPRO is slowly dying over here

<<BTW, you get a better chrominance with Beta SP than with DV. >>

yeah, but the picture's not as clear IMO

<<DV does yield more lines of resolution, but at 1/2 the color sampling. I personally think you get better picture with DV, but that's just me>>

i agree with you.

anyway,

Nick "Shorty" Long

 

I guess the UK is accepting it a bit more than the USA

There is a gargantuan difference; UK uses PAL

In the US they are stuck with the 4:1:1 color space on DV... which means 4 horizontal pixels share chroma.

A dead monkey strapped to the hood of a speeding car could pick out the chroma bleed on the edges of that footage.

In PAL the DV colorspace is 4:2:0 which means that while still being a 1/4 ratio, it is instead a 2x2 pixel block that shares chroma, NOT a 4 pixel horzontal stretch.

Its way harder to see any chroma bleed in PAL footage.

I dunno anyone serious about filmmaking should get a PAL DV camera instead. 25 "film like" fps and higher resolution and better color sampling. What could be better?

/Z

 

I'm with ya masterzap, we yanks got the shaft on that one

 

Hmmmm. That's the one thing that could prompt me to get any camera but my GL-1. It's only weakness is that "DV edge" you get sometimes.

If there were a 3 CCD camera that had that improved chroma preservation (PAL, I suppose), could shoot in a progressive mode of sorts, and even better if it had the option of shooting at 24/25 and 29.97, I'd definitely check it out and probably go for it. You can always just render back out in NTSC, right?

Upon considering, I must ask. With this extra chroma info preserved, what other visual information is lessened here?