Uprezzed?

[Graeme Nattress]

Absolutely! Because most of use can't afford HD, but we can afford DV. My goal is ALWAYS to get the best from modest equipment. DV provides a very high quality, stable, digital picture. It may have artifacts, but they're able to be dealt with. The chroma sampling is NOT an issue with DV if you use clever algorithms. You just have to know how to decode the lost chroma info from the luma, which is a technique that you can't use on SP because it's fuzzy in the chroma.

Graeme

Rafael I'll let Graeme answer that one respectfully.

My opinion is DV is DV if you want something more robust you should start with acquisition. You will spend just as much time and money trying to “upress” DV to another format CODEC while compressing it twice as much by the time you’re done. If Graeme can invent a lossless plugin that cost less than a one off DV to SDI/HD upconverted dub than I’ll take notice.

[Graeme Nattress]

This is what I'm doing today on DV chroma reconstruction:

http://www.nattress.com/filmEffectsGNicerTests.htm

Combine that with the algorithm I'm working on for uprezzing the whole image (luma and chroma) which I posted an early test of, and you can see that I believe that I can make DV look an awful lot better than it deserves to. One of the nice things I've found so far about the algorithm is that it sharpens video without putting those nasty sharpness lines around edges, and will even remove some of the bad effects of existing sharpness lines. But I'm probably a year away from a fully working version....

Graeme

I'm wonder that R&D buget and market demand will offset an inexpensive solution. I can't fault you for thinking out side of the box.

Graeme, Question:

Why not invent a hardware cuicit that is inside of the DV camera that will do this "upress" converion realtime while aquiring the footage?

[Graeme Nattress]

The best thing about DV is that it's standard and affordable. If you uprezzed inside the camera, how would you store it??

Anyway, I'm not an electronics person, I'm software, so I do what I do best.

I'm self funding the R&D - it will get expensive in the end when I have to compare what I'm doing to "real" HD, but I also have some other R&D projects which are cheaper and should help fund the big one....

Graeme

how would you store it??

I guess you colud tweek the codec or step on the compression a little.

Thanks

[Rafael Cruz]

Mr. Nattress after reading and looking at your page i think the Film Effects: G Nicer chroma reconstruction is awsome and is far better than doing nothing to it. is it better to apply this filter to an uprezzed picture let say a 2k or hd res? or will it yield the same results on a standar dv 720*480 image? also would it be sound to apply a sharpness filter after the chroma reconstruction? is really a shame that i only have a PC cuz i belive that your software is for the MAc i have premire pro and a matrox rtx100 system. is there a way that i could do this kind o job to my footage using a pc? have u ever try to write filters for virtual dub or avisynth? thanks again

[Barend Onneweer]

Why not invent a hardware cuicit that is inside of the DV camera that will do this "upress" converion realtime while aquiring the footage?

Erick, you seem to be so sure of yourself and why there's no point in trying to reconstruct the chroma detail, but here you clearly show that you have a limited insight in the way that the different video formats work.

The chromaresolution in DV (and HDCAM for that matter) is reduced in the encoding stage, before the signal goes to tape. Before the video is compressed in the camera, the resolution is there, but it's downsampled to cut bandwidth.

So there's no need to upres in-camera, since the resolution is already there.

The point is that the chroma of DV and HDCAM comes out very pixelated. The human eye is rather unsensitive to color detail, which is why they can get away with it. But for processing like color correction and chromakeying, you want to have that information. A good solution to reducing the pixellation of the chromachannel is to resample it using a good scaling algorhythm. Although you end up with an image the same size, it'll be less pixellated and smoother, withouth blurring.

A plugin that does this is the de-artifactor that comes with Magic Bullet Deinterlacer. Just a simple test with this shows that there's a HUGE benefit in reconstructing chromadetail on DV footage before processing it.

Obviously shooting at uncompressed HD would be prefered technically - but that's not the point.

Just to set things straight.

My apologies Barend,

I was being flippant regarding the upress circuit, and just to set things straight, I’m not a video engineer but I do understand tape formats professor.

I question your logic:

“Before the video is compressed in the camera, the resolution is there, but it's downsampled to cut bandwidth.

So there's no need to upres in-camera, since the resolution is already there.”

-What resolution is already there? please be specific.

“resample it using a good scaling algorhythm”

-good idea! But why spend hours or possibly days rendering with an expensive plugin when you could do this real time in the cameras circuitry when it is encoded to tape?

Check out the Cannon XL2, you will find new circuitry built in to the camera to get a closer to film look when acquiring (no plugin needed), not to far off from my idea.

thanks

[Barend Onneweer]

Like I tried to explain earlier, the chroma resolution loss happens at the stage of compression to DV. This is just part of the DV format, that the chroma channel is downsampled. There's no way around that as long as you write to DV tape.

It's just the limitation of the DV format. And the HDCAM format for that matter. And although the XL2 may have slightly higher resolution chips resulting in a sharper image, the image that goes to tape still has it's chroma downsampled at the DV compression stage. This is what they mean by 4:1:1. For each 4 samples of luma information, only 1 sample of chroma is stored on the DV tape. So the only way around it is use a more expensive tape format, Digibeta or HDCAM SR - or start thinking about recording directly to disk...

Ideally you'd record 4:4:4 but that's a huge amount of data, so for practical reasons most digital formats use some kind of chroma downsampling.

Hope this helps.

Bar3nd

DVCPRO 50 is 4:2:2

[Gerald Baillgergeau]

Would using DVCAM tape instead of miniDV inprove the image quality?

[Barend Onneweer]

DVCPRO 50 is 4:2:2

Yes, and so is DigiBeta, albeit with a less harsh compression ratio and thus a higher bitrate.

But I fail to see how this adds to your point. The XL2 doesn't record to DVCPro50. And the 50 means that it's got a double datarate (50mbps) compared to DV25's 25mbps - it's essentially one of the more expensive tape formats that I was referring to in my previous post.

Recording to DVCAM instead of DV doesn't help either. The codec for DV and DVCAM is exactly the same. The most obvious differences are that DVCAM has a higher tapespeed so it's less prone to dropouts due to dirt on the tape. And DVCAM has locked audio.

Bar3nd

[Les Dit]

If you think it's possible to uprez a DV camera to HD, then I'm going to uprez my HD camera to be IMAX. ;-)
-Les