HDV problems gone?
 

I just came across this article and wanted to get some feedback:
http://www.studiodaily.com/studiomon...ssue/7292.html

Supposedly, with this peice of gear, 1000 USD, a decent computer 2500USD, a HDV deck (2500) and a HD-sdi capture card (1200) , it simplifies the HDV workflow, and makes it better, supposedly...

It says that you can import HDV material into a HD-SDI uncompressed project. What if all you had was HDV matieral? Through this, you get 4:2:2 color space, eliminate the long GOP, the only problem is the massive amount of hard drive space needed.

Am i right in thinking this is the solution for HDV: in which you can dub out to HDCAM, DVCPRO HD , eliminate the long gops, keep a high color sampling space, etc. Seems perfect!

Also, just to add, the whole point of this post is to figure out a workflow in which we skip the compression of firewire and how that affects the quality of the footage...

That being said, the AJA capture card, xena lh/e mentions this "analog component connections from HDV cameras that allow direct ingest of HDV-acquired material into uncompressed projects". So, if we directly connect to the capture card (not thru firewire) we will avoid firewire's compression during captures?

It doesn't solve the compression issue. If you shoot HDV to tape, it then gets compressed MPEG-2 with the GOP. Running it thru this device doesn't get rid of that. What you can do with that workflow is capture HDV as a different codec, like DVCPRO HD or uncompressed 8-bit HD. What the advantage to that is that you have a better colorspace and compression for color correction and effects. Renders are faster, and outputting is easier.

The only way to avoid the compression is to capture directly from the camera thru that device and bypass the tape recording.

Ah, i see what you're saying, i realize that as soon as you shoot to tape you are compressing it, HDV is the codec!

Thanks for clearing that up! Is the extent you can tweak the previously HDV footage in 4:2:2 workspace significantly better than say native HDV post color correction/tweaking?

Im not sure i understamd why you would need the hardware. Couldnt one just capture in HDV and then export out to the desired codec. What can the hardware do that the software cannot?

Cheers,
Ben Gurvich

The hard ware is for bypassing firewire transfer from HDV deck/camera to the computer. Soona s you hit firewire there is a 5 to 1 compression, i believe.

The hardware allows you to capture via HD-SDI pipeline into a hardware capture card (on your comp thru pci/pcie) and it lets you work HDV footage (which is now captured to a different format) in a 4:2:2 environment. This means you get to tweak the image more than you could in a traditional HDV sequence/project and you have access to real HD monitoring (thru HD-SDI to a broadcast HDmonitor), you get rid of long GOP , uncompressed HD if you wish, you have the option of dubbing out to HDCAM, etc.

Note, this is probably not realistic for anyone unless they are trying to do network projects. HDV is beautiful when it is shot right, I'm trying to get the most out of the color space via this method..BTW, anyone feel free to correct me if i'm wrong about any of the above ifo.. :)

Can somebody confirm or disprove (hopefully) the statement that firewire adds 5:1 compression?

I've never heard that before.

Use of a firewire connection does not add any compression to anything. The HVX-200 outputs 100 Mbps DVCPRO-HD via a firewire port. The only limit is the data rate of the sending and receiving units, up to the 400 MB maximum that the firewire port can handle (800 MB on special firewire ports).

FireWire does not "add" any compression. It's simply a pipe through which data moves, from one device to another. DV compression has *always* been 5:1, that's where that ratio comes from.

oops, thanks for the correction. I got that tangled up!

Anyway, i've color corrected HDV footage before, and there is not a lot of leeway. I've never touched 4:2:2 uncompressed material before. This route allows you have this color space, just how much is it possible to tweak the image around?

Even if you convert HDV to a 4:2:2 codec, you're not going to get 4:2:2 values.

Isn't that sort of like scanning a black and white faxed piece of paper into a scanner at 600 dpi? You're not going to gain any info that wasn't there to begin with. Just because it's a bigger hose, doesn't mean there's any more water.

If you want 4:2:2, you need to capture 4:2:2 like the HVX does. You'd have 100 mbps (DVCPRO HD) instead of 25 (HDV) and more color info.

With the device linked to, all you'd be doing is wasting hard drive space. Someone please correct me if I am incorrect.

Scott

hmm, i see what you're saying. So basically, that setup is to let you bypass the Long GOP of HDV, and capture to a codec such as DVCpro HD ....

Also, couldn'y you capture HDV thru analog HD to a capture card like Kona/AJA? Why would this be better (or not) than firewire?

There can be, under certain conditions.

If the footage is noisy low-light (even 0db gain), then the codec introduces more blocking because it can't handle the extra high-freq info. Try to bend the image around in CC and the blocking comes out. Pretty bad looking. I shot a concert with 9 Sony Z1s a long while back where the base light level left a lot to be desired, and in the end the show looked like it could have been shot with regular 30p DV.

If you have a real clean image shot with plenty of light, then things get a lot better.

If you downconvert the HDV to uncompressed 10bit SD (for an SD deliverable), and THEN color correct, it gets even better, because a lot of the blocking gets averaged out in the downconvert.

The cleaner the camera head, the better the codec performs. Stuff from my F350 at 35mbits is a much different animal to color correct for all the above reasons, plus the extra 10mbits.

I see what you are saying Nate. The fact that you can now convert the HDV to DVCPROHD(or uncompressed) using the convergent design/hd-sdi is a bit confusing... Does this now give you that extra color space for CC or is it simply just a workaround for eliminating long gop?

The way I see it, it's a workaround for NLEs that don't have very good HDV/MPEG support quite yet.

A lot of people that work in Avid and have existing workflows in place for episodic TV can use a solution for HDV that doesn't involve native HDV use, nor dubbing all their HDV reels to HDCAM (like a lot of shows have done in the past).

In my experience, transcoding HDV to another codec always brings out anywhere from a little recompression artifacts to a lot, so I never do it unless I absolutely have to. My experience does not apply to the Cineform products though, most users say that transcoding to that looks great.