Comments

MozartMan wrote on 1/6/2012, 8:06 AM
Patrick,

Why do you need HDMI input card? HV30 uses HDV format and has FireWire output and you can capture HDV video with Vegas very easy via FireWire and without re-encoding.

But if you really need card with HDMI input I would recommend this one:

Hauppauge Colossus PCI Express Internal HD-PVR

I use it to record video from DTV HD PVR to my HTPC via HDMI. It re-encodes video in H.264 format but quality is identical to DTV.
craftech wrote on 1/6/2012, 8:43 AM
Have you tried DVI. You can route the audio separately.

John
Steve Mann wrote on 1/6/2012, 10:51 AM
I am with Patrick here. The HDMI output from the camera is before the compression into HDV or whatever the cameras digital output. I am also looking for a reasonably priced HDMI camera and capture card for greenscreen use.

The problems I have found are that one, the Black Magic Intensity does strange things to the black levels. (Someone on this forum found this error, but I don't recall whom and I can't find the post). I don't know about the HV30, but most consumer cameras with HDMI output don't pass along the full 4:4:4 colorspace, but rather a subset - usually 4:2:2.

So, jmpatrick, (real name withheld), what is your goal for capturing HDMI?
jmpatrick wrote on 1/6/2012, 11:43 AM
Lots of HD vacation footage. Hawaii, Rockies, etc. I have a new machine with a Blu-ray burner and I want the most possible out off the HDV tapes.
Former user wrote on 1/6/2012, 12:54 PM
Steve,

Once it is recorded to tape or flash card, it is compressed isn't it?

The HDMI would be less compressed if used live, I would think.

I don't know for sure, just asking.

Dave T2
MozartMan wrote on 1/6/2012, 1:28 PM
@Dave T2

Yes, when camcorder saves video to tape in HDV format it is compressed at the ratio of between 47:1 and 27:1

If Cannon allows video to pass through from lens to HDMI out without any compression, then captured video will still be compressed with HDMI capture card.
jmpatrick wrote on 1/6/2012, 2:13 PM
That appears to be the case, upon further reading. The HV30 will pass a 1920x1080 live image directly out of the HDMI port only, not from HDV.

Thanks. Saved me $180.

jp
R0cky wrote on 1/6/2012, 2:29 PM
Actually, you saved a lot more as you'd need a fast disk array to capture that data. There is no way your disk is fast enough to ingest 1080i uncompressed at full speed.

Black Magic has a new little gizmo with HDMI input that you plug in a solid state drive just for this kind of application. Gizmo plus drive is maybe $1000.

And the drive will fill up fast with uncompressed data so you need a few of them.

rocky
Steve Mann wrote on 1/6/2012, 3:07 PM
"Once it is recorded to tape or flash card, it is compressed isn't it?

The HDMI is uncompressed in all cameras I looked at, but the problem I found was that the sub $1,000 cameras don't output the full 4:4:4 colorspace. When the data is written to the media, the CODEC in the camera compresses the video.
farss wrote on 1/6/2012, 3:15 PM
"The HV30 will pass a 1920x1080 live image directly out of the HDMI port only, not from HDV."

Even if it would and I'm surprised it doesn't, most cameras do let you play the tapes back from the tape via the HDMI port, doing that achieves NOTHING.

The images on the tape are already compressed, whatever loss was incurred by the compression cannot be undone. If anything playing the tape back via the HDMI port and capturing from that is going to degrade the image quality further.

It doesn't really end there. Even capturing the HDMI output from the camera before the images are recorded to tape may not yield a large improvement in the image quality. It may be of some benefit if you are shooting green screen but that's about it. The explaination of why this is the case is rather longwinded, if anyone wants to know I'll give it a shot.

Bob.

Steve Mann wrote on 1/6/2012, 7:46 PM
"most cameras do let you play the tapes back from the tape via the HDMI port, doing that achieves NOTHING"

Bob, I'm not sure whom you are directing this to. I am looking for a consumer camera that sends the 4:4:4 colorspace to the HDMI port for green screen captures.

I realize that the first "4" refers to the green channel, which is where all digital cameras get their luminosity information, and I haven't seen a colorspace that isn't 4:x:x. The problem is that when the resolution of the red and blue channels is compromised in compression, then the chromakeying around the fine details of the not-green pixels suffers. That is why I want to get 4:4:4 out of the camera.

Steve
Former user wrote on 1/6/2012, 8:43 PM
Steve,

I think what Bob is referring to is, once the video is recorded onto the tape, it is no longer 4:4:4: unccompressed. So playing the video off of the tape thru the HDMI gains you nothing. It is already compressed. The only way HDMI uncompressed works with this camera, and many others I assume, is if you use the camera to record live thru the HDMI to a device capable of capturing uncompressed video, such as a computer with a high data rate drive.

Dave T2
farss wrote on 1/7/2012, 4:57 AM
"The problem is that when the resolution of the red and blue channels is compromised in compression, then the chromakeying around the fine details of the not-green pixels suffers. That is why I want to get 4:4:4 out of the camera."

DaveT2 explains it above. The damage was done during the 4:2:0 choma subsampling used in the HDV compression. There's also other compression artifacts of course but let's ignore that.

When you play the tape back the recorded signal is indeed decoded to 4:4:4 and that's what comes out the HDMI port. It's also EXACTLY what happens in Vegas or any NLE after you've captured the tape. Vegas decodes the HDV to uncompressed Y'CbCr and then to RGB. The chroma sampling is now 4:4:4. Neither path can restore the missing chroma data, the green or whatever pixels the keyer needs just didn't make it onto the tape and nothing can recover them. There are some tricks that make their loss less obvious but they're just smart guesses.

Now comes the really nasty bit.
You'd think, OK lets bypass the tape and go straight from the camera via HDMI and capture that, goodbye HDV compression, goodbye 4:2:0 and hello 4:4:4. Even better you can buy a BMD Hypershuttle for peanuts and you're good to go, right, well not exactly.
The problem is what is it that is being sampled at 4:4:4?
The sensors in the cameras that most of us can afford cannot resolve 1920x1080 in R,G,B. In fact if we're spending a fair bit of money on your cameras then they can barely manage that with the luma part of the image and that's all you look at on a resolution chart and it is what our eyes are most sensitive to as well. Which as you rightly noted is why the first number is pretty well always "4". If you were to use a resolution chart that was say red and blue you'd get quite a shock.
The reason is single chip cameras use Bayer pattern sensors, they sample RGB at different points in the image. From that they can derive a pretty good resolution luma signal but the CbCr signals (the chroma / color) information is not as high resolution.
Even when you go to more expensive cameras with three chips the designers may still make compromises using things such as pixel shifting. That means each of the three sensors still cannot resolve 1920x1080 of red or green or blue. Generally they'll be better than a single chip camera but it might not be a massive leap either.

What all this means is, yes, recording uncompressed directly from your camera via HDMI will give you a somewhat better key than you'll get from what was recorded to tape. Working against you is the increased cost of your recording media. The Hypershuttle is cheap, the media for it is around 10x the cost of the unit and you will fill it up quickly. You could use a recorder like the Samurai. It is more expensive but it can record Prores or DNxHD both of which codecs use some compression which will reduce your media costs a bit but you're still looking at around $1K for the unit and around the same for the media unless you use spinning disks.

Just as an aside and to show how you can be misled by the way "4:4:4" gets bandied around. The first HDCAM cameras use 3:1:1 sampling.and they don't look too shabby even today.

Bob.