Recording uncompessed for keying

[Christian Schmitt]

After getting mediocre results from keying xl2 DV footage, I´m thinking about getting a videocard that let´s me capture uncompressed or just better than DV quality color wise...
Does anyone here do this on a regular basis?
Like with a Decklink?
Does anyone key through the Y/C of the XL2 or his miniDV?
For a friends project, we´re thinking of renting a HVX200, anyone keying with the component-outs of the HD(V) cameras yet?

[Keith Wakeham]

Well if your talking XL2 then I think HD/HDV acquisition is the wrong forum.

What I've seen done is using an XL1s into a BETAsp deck with good results. Keying was done on an avid Symphony in 4:4:4 uncompressed (captured over analog component). It was explained to me that the colour space made it easier to key even though it had to pass through analog.

A real pro card should show some benefit rather than a cheaper consumer card. Decklink SP or Decklink Extreme seem like good choices. Sorry I haven't used them though so can't tell you what they are like to use.

[Christian Schmitt]

Well,
I´m thinking on renting the HVX200, as stated, and record 720p at different framerates and capture directly to a PC...
Just wanted to get some advice on that...
The XL2/s-video way was only loud thinking, more or less...

[John Rofrano]

I do chroma key work with my Sony Z1 and Serious Magic Ultra 2 software. I don’t use uncompressed but the results are still far better than anything I could key with DV. I think the added resolution of HDV is enough for most situations. Ultra 2 is also an outstanding piece of software. It makes it very easy to get a good key even under band lighting conditions.

You might want to try keying with compressed HDV first and see if you like the results before you jump though hoops to capture uncompressed off the camera. I believe you need a RAID 0 with at least 5 drives to keep up with uncompressed HDV capture so you are talking some serious equipment.

~jr

[Rafael Cruz]

Originally Posted by John Rofrano

I do chroma key work with my Sony Z1 and Serious Magic Ultra 2 software. I don’t use uncompressed but the results are still far better than anything I could key with DV. I think the added resolution of HDV is enough for most situations. Ultra 2 is also an outstanding piece of software. It makes it very easy to get a good key even under band lighting conditions.

You might want to try keying with compressed HDV first and see if you like the results before you jump though hoops to capture uncompressed off the camera. I believe you need a RAID 0 with at least 5 drives to keep up with uncompressed HDV capture so you are talking some serious equipment.

~jr

im also trying to get more info on capturing from component of the fx1, as John said capturing uncompress HD is an expensive operation, but if we could capture and encode it live to a better codec ,lets say dvcpro HD @ 8bit, the 4:2:2 color space will be great for keying, KONA LH capture card is soppoused to have analog input and output, for PC there is a new codec from DVFILM guys,the raylight that will let dvcpro HD be edited in Vegas, so now theres no need for expensive raid arrays to capture to a better compresion as i belive one could work with dvcpro HD with a good SATA HardDisk as a couple of 300gb HD will give like 12 hours of storage i think maybe 50GB/hour .

[Ken Hodson]

In that situation one would have to ask if DVCproHD IS an improvement over HDV? That is a lot of extra cost/effort to go to another highly compressed codec. You will loose resolution by going to DVCproHD. Yes you will get 4:2:2(at a lower resolution), but for example, head to head tests based on the HVX200 using DVCproHD at 4:2:2 did not show any improvement on keying over an HD100 HDV 4:2:0. I would check out SheerVideo by BitJazz or another codec option.

[Christian Schmitt]

With the HVX I would pobably just record in DVCproHD, no Decklink needed (well, some claim recording to DVCproHD via the component out yields better result...)
I like Ken´s idea with the SheerVideo codec:
Can I just tell the Decklink what codec to use?
Can I use SheerVideo for the live encoding with a Decklink?
Would I need a maxed out box for this, with latest dualcore proc, maxed Ram, raid setup aso...?

[Douglas Spotted Eagle]

As Ken pointed out, there is no advantage of DVCProHD over HDV from the JVC HD100u, but I don't believe it's related to DVCProHD, it's related to the difference between significantly resampled pixels vs full raster pixel/no resample. Shooting DVCProHD with a larger imager makes for a more obvious difference, but not as obvious as most folks might think.
To use the Sheer/Bitjazz codec, you'll want a fast RAID more than anything else. The CPU isn't nearly as important as thruput.

[Rafael Cruz]

Originally Posted by Douglas Spotted Eagle

To use the Sheer/Bitjazz codec, you'll want a fast RAID more than anything else. The CPU isn't nearly as important as thruput.

Fast Raid for PC isnt too expensive at all with $79.00 dollars Mainboards with 4 SATA ll conections and $250.00 dollars 500GB SATA ll harddisks, what do you guys think ? is 300mb/sec transfer rate enough to for live capturing of sheer encoded video? but what i would really like to know is if the declink or kona cards can encode live to sheer codec? and how much video time will you get per Harddisk GB? how much of that 300mb/sec will sheer will use ?

65% less space needed than uncompressed video with almost the same quality is a lot. maybe this is getting interesting. ahh and another big question, does the new cards from aja or blackmagic (decklink,xena LH) can capture from the component output?

[Christian Schmitt]

Originally Posted by Douglas Spotted Eagle

As Ken pointed out, there is no advantage of DVCProHD over HDV from the JVC HD100u, but I don't believe it's related to DVCProHD, it's related to the difference between significantly resampled pixels vs full raster pixel/no resample. Shooting DVCProHD with a larger imager makes for a more obvious difference, but not as obvious as most folks might think.
To use the Sheer/Bitjazz codec, you'll want a fast RAID more than anything else. The CPU isn't nearly as important as thruput.

So for me this narrows down to two options:
recording DV100 in 720p via firewire OR recording SD uncompressed (well, SheerVideo encoded if possible with the Decklinks/AJAs...?) via analog-out straight to disk.
Which way to go...?
Douglas, there really seems to be some controversy about wether DVCproHD is really better than HDV,
are your observations based on Adam Willts test?
Maybe it is just so hard to believe for me, that 100Mb/s DV100 isn´t better than 25Mb/s HDV,
hell, it should be around 4 times the information!
I´ve seen good looking footage from maybe all the HD cams outthere,
if this project wouldn´t be 95% greenscreen, I´d be happy with most cams.
But here the focus becomes so technical that decision making becomes so hard...
Thanks for all the answers so far and please keep on posting!

[Brian Luce]

Originally Posted by Ken Hodson

but for example, head to head tests based on the HVX200 using DVCproHD at 4:2:2 did not show any improvement on keying over an HD100 HDV 4:2:0..

did you perform these tests yourself? first time i've heard that and it's not what i would have expected. got any more info?

[Douglas Spotted Eagle]

Originally Posted by Brian Luce

did you perform these tests yourself? first time i've heard that and it's not what i would have expected. got any more info?

I don't know if Ken tested this himself or is going by posts, but I did the same thing comparing all of the HD cams (Z1, A1, HD100, XL-H1, HVX200).
Same results as Ken comments upon.
In fact, there is a mask image in my book on HDV showing the key from a Z1. It's visibly smoother/less aliased than the same mask image from the HVX.

While packaged in a 4:2:2 DVCProHD stream, the image is so starved, it's garnering significantly less chroma and luma well before it's being processed.
JVC=1280 x 720 full raster imager/sample
HVX=720 x 540 imager/pixelshifted to 1280 x 720
PAL DV=720 x 576 full raster imager

[Ken Hodson]

Yes I am just going off of various user reports/posts. I have only used JVC HDV myself. Here is a current article comparing both cams with a specific test using blue screen.
http://www.bluesky-web.com/HDVHVX.htm