Uncompressed DV25

James Rogers · February 9, 2005

Hello,

We are having a discussion at IndieClub.com about the possibility of recording uncompressed video from a prosumer MiniDV camera to a computer hard drive. There are some that believe that a live video feed transferred through the firewire to the computer will produce uncompressed video. I personally don't believe this. However, I think that the analog outputs are uncompressed. One of our members suggested that I pose the question here. He claims that professional DPs capture uncompressed video from DV25 cameras as a matter of common practice. If this is true, could someone please explain how.

If you have time, stop by www.indieclub.com and say howdy.

Oh yeah, I'm James Rogers. Here is my website: Morphic Motion

nchopp · February 9, 2005

The camera is compressing the signal before it even hits the tape. Everything you get from a compressed format camera is compressed; tape, analog outs, digital outs. There's no free lunch. ;-)

James Rogers · February 9, 2005

First let me fix a mistake. The person who claims that a prosumer camera (canon, sony) can deliver uncompressed video said that you have to use the y/c out and not the firewire.

Now, for the sake of clarity, I'm not talking about recording to tape. That is not what I said. I said "a live video feed transferred through the "y/c out" to the computer will produce uncompressed video". In other words; if you turn the camera on and record directly to the harddrive through the y/c out, you can get uncompressed video.

Any thoughts?

Edited February 9, 2005 by James Rogers

Phil Rhodes · February 9, 2005

Hi,

If you have an analogue uncompressed capture board and you're recording the Y/C output, then yes, that'll usually be uncompressed. However, it won't necessarily look any good, or even better than the DV, because of the limitations inherent to analogue video and cheap consumer cameras in particular.

Phil

James Rogers · February 9, 2005

Phil,

In terms of artifacts; When shooting blue/green screen, would it be wiser to capture analog as described above? Also, why do you say the image might not look any good if you capture analog from a prosumer MiniDV camera?

John Ealer · February 9, 2005

First let me fix a mistake. The person who claims that a prosumer camera (canon, sony) can deliver uncompressed video said that you have to use the y/c out and not the firewire.

Now, for the sake of clarity, I'm not talking about recording to tape. That is not what I said. I said "a live video feed transferred through the "y/c out" to the computer will produce uncompressed video". In other words; if you turn the camera on and record directly to the harddrive through the y/c out, you can get uncompressed video.

Any thoughts?

<{POST_SNAPBACK}>

The Y/C or S-Video output is, as you mention, analog; hence the term "compressed" or "uncompressed" is not very useful, nor accurate. Of course it's not compressed in a digital sense - because it's analog! But it's not even component analog, it's a pseudo-component scheme where luminance (Y) and chrominance © are delivered as separate signals. This differs from true component analog where video is formed from a luminance and two chroma-difference signals. (YPbPr).

The question to ask is what you gain from digitizing the Y/C signal as uncompressed digitial video (Rec. 601 4:2:2 component digital) as opposed to recording in camera as DV25, which while compressed and subsampled, is still a true digital component format. Keep in mind that the Y/C output has gone through another D-A (digital to analog) conversion to get to that S-video signal that you are then going to DIGITIZE all over again, when you record to your hard drive. As you know, it's best to keep the number of A-D / D-A conversions to a minimum.

The only potential advantage I see in recording that S-Video output is that if you're doing greenscreen or matte work, avoiding the 4:1:1 subsampling in DV would be desirable. Other than that, I really don't think you have a lot to gain. I personally think you'd be better off dealing the the intraframe M-JPEG compression in DV than with the color anamolies in Y/C.

My other thought is that if you're spending all this time and money to record to a hard drive, why not just shoot with a better camera and avoid all the hassle all together? Shooting DVCPRO50 (my fave), MPEG/IMX or Digbeta will give you significantly better results than relying on that compromised Y/C video output OR shooting DV25.

J

John Ealer · February 9, 2005

James -

I would also add that NO commercially available camera outside the Sony F950 (dual link HD-SDI) or the Thomson VIPER (in Filmstream) will output 4:4:4. Keep in mind that UNCOMPRESSED digital compoent video, according to the Rec. 601 specification, is 10 bit 4:2:2 subsampled digital component video. The SDI output of a Digibeta camera or deck is exactly that, 10 bit 4:2:2.

I wouldn't expect something out of a consumer DV camcorder that Digibeta or DVCPRO50 cameras can't do ;)

J

Patrick Neary · February 9, 2005

...also remember that most, if not all prosumer/consumer camcorders are blessed with lenses that are junk. trying to get a better signal from a camera head that can barely produce DV-quality images seems kind of pointless....

Phil Rhodes · February 9, 2005

Hi,

> When shooting blue/green screen, would it be wiser to capture analog as described

> above?

On PAL no, on NTSC maybe - I've heard a lot of people say it helps because NTSC subsampling is very asymmetrical.

> Also, why do you say the image might not look any good if you capture analog from a

> prosumer MiniDV camera?

I didn't say it wouldn't look ANY good, but mainly I tend to mention things like that because people tend to assume that camera equals camera if they both happen to record DV, even if one costs thirty grand and the other costs three. Plug a PD-150 into a monitor, plug a DSR-500 into a monitor, switch between them, which looks better - you figure it out. Cheap cameras look cheap.

Phil

nchopp · February 9, 2005

For your average screen work, something like the 150 will be fine - the key is just lighting well... If you're doing something for broadcast or DVD, a camera like the 150 will be sufficient.

Valeriu Campan · February 10, 2005

The only pro/con sumer camcorder that I know of having analog component output is the Sony FX1/Z1. I think, correct me if I am wrong that some bigger ones like DSR570... have component pins in the connector for the CCU and a custom cable can be made for it.

You can take the analog component signal before it goes to tape and record it through an A/D converter from Kona or BlackMagic Design direct to disk. The chroma sampling and compression can be done at this stage being dependent of your hardware/software combo.

John Ealer · February 10, 2005

On PAL no, on NTSC maybe - I've heard a lot of people say it helps because NTSC subsampling is very asymmetrical.

<{POST_SNAPBACK}>

NTSC DV25 is quite problematic for exactly that reason, the 4:1:1 chroma subsampling leaves you with "wide skinny" blocks that are difficult to get smooth mattes out of. It can be adequately managed with tools like FCP's 4:1:1 Color Smoothing...but since you basically only have 180x480 resolution in your chroma channels, you're never going to get a very sharp matte.

J

nchopp · February 10, 2005

NTSC DV25 is quite problematic for exactly that reason, the 4:1:1 chroma subsampling leaves you with "wide skinny" blocks that are difficult to get smooth mattes out of. It can be adequately managed with tools like FCP's 4:1:1 Color Smoothing...but since you basically only have 180x480 resolution in your chroma channels, you're never going to get a very sharp matte.

J

<{POST_SNAPBACK}>

I disagree entirely. I pull quite solid mattes off DV25 material as a matter of course, and without the FCP color smoothing. Boris RED does a great job of keying DV25 material.

John Ealer · February 10, 2005

I disagree entirely. I pull quite solid mattes off DV25 material as a matter of course, and without the FCP color smoothing. Boris RED does a great job of keying DV25 material.

<{POST_SNAPBACK}>

As I said, the quality of DV25 chroma keys are adequate when handled well, as you have obviously done. (While I don't know Boris RED, I can't imagine that its keying filters do not include some kind of color smoothing for DV). In comparison with other formats like Digibeta and DVCPRO50, the results from DV25 are inferior. It just depends on how demanding your final delivery specs are.

J

nchopp · February 10, 2005

As I said, the quality of DV25 chroma keys are adequate when handled well, as you have obviously done, (While I don't know Boris RED, I can't imagine that its keying filters do not include some kind of color smoothing for DV). In comparison with other formats like Digibeta and DVCPRO50, the results from DV25 are inferior. It just depends on how demanding your final delivery specs are.

J

<{POST_SNAPBACK}>

Oh, very true. I'd take DigiBETA or DVCPRO50 over DVCAM any day.

Edited February 10, 2005 by nchopp

James Rogers · February 10, 2005

This is a pretty good thread. Thanks guys, I'm learning a lot from you folks.

John Ealer · February 10, 2005

There are some that believe that a live video feed transferred through the firewire to the computer will produce uncompressed video. I personally don't believe this.
<{POST_SNAPBACK}>

You are absolutely right, all miniDV cameras send a DV25 (8-bit 4:1:1 with intraframe M-JPEG compression) signal over firewire. DVCPRO50 Decks will do DVCPRO50 (8-bit 4:2:2 with intraframe M-JPEG compression) over firewire. DVCPROHD over firewire has been implemented as well, but that's far from uncompressed either.

While it's conceivable that some clever mind may yet devise a way to pipe uncompressed component digital video through one of the current or future firewire specs, it's not being done right now. Uncompressed Rec. 601 digital component over SDI uses 270 Mb/s, so it would seem they are a little ways off. Maybe when they roll out Firewire 1600?

J

nchopp · February 10, 2005

You are absolutely right, all miniDV cameras send a DV25 (8-bit 4:1:1 with intraframe M-JPEG compression) signal over firewire. DVCPRO50 Decks will do DVCPRO50 (8-bit 4:2:2 with intraframe M-JPEG compression) over firewire. DVCPROHD over firewire has been implemented as well, but that's far from uncompressed either.

While it's conceivable that some clever mind may yet devise a way to pipe uncompressed component digital video through one of the current or future firewire specs, it's not being done right now. Uncompressed Rec. 601 digital component over SDI uses 270 Mb/s, so it would seem they are a little ways off. Maybe when they roll out Firewire 1600?

J

<{POST_SNAPBACK}>

Possible, but we're still not even seeing FW800 on cameras yet. :-\ The only real things we're seeing that are 800 are hard drives.

James Rogers · February 10, 2005

What about the Andromeda capture device by ReelStreem? You guys seem pretty smart. Take a look at their website and see what you think of their device. It is something that has to be hardwired into the camera. It is suppose to bypass the compression circuitry of the camera and send an uncompressed digital stream to your computer via USB2. I think their software also allows you to set certain perameters such as color sampling too. The video is saved as individual bitmaps rather than avi or mov .

Here is a link to their site: Reel Stream

Edited February 10, 2005 by James Rogers

John Ealer · February 10, 2005

My two cents regarding the ReelStream beta product:

The tantalizing technical concept behind the device is certainly solid and theoretically possible and plausible - but I don't see a great number of applications for it.

If I'm using a small DV camera, it's because the producer wants something that's fast, mobile and cheap. Adding this device to the miniDV camera takes away all three of these advantages, and introduces a much more time intensive post-production flow. And it does nothing to improve upon two of the drawbacks to any small camcorder: 1/3" sensor size (which means lots of depth of field) and one-size-fits-all mediocre optics. I'd also be concerned about the robustness of the system - how buggy or prone to crash would the hardware and software be?

So while I could see this product having a certain usefulness, say for the low-budget producer who needs to occasionally do some greenscreen work but doesn't want to have to rent a higher-end camera, I'd tend to think that by the time all the costs are added up, most folks would be better served jumping up from miniDV to DVCPRO50/HD or HDV.

FWIW.

J