4k DCP vs 2k DCP for 2k projection

[Patrick Tresch]

Hello,

I'm mastering a short shot @ 5k and finished in 4k, and was wondering if a properly downscaled 2k DCP would hold better resolution than a 4k DCP if it's aimed at a 2k projector?

There will also be some 4k projection in the near future, so an only 2k DCP is not the plan.

As I understand, modern server can handle 4k DCP without problems and scale them to 2k for the 2k projector, but I wonder if the downscaling is made by pixel skipping or is it a hardware downscale and if it's good enough?

Any input would be appreciated. It will determine if we will have to make both packages.

Thanks

Patrick

[Graeme Nattress]

There's obviously many ways a projector (or server) could make a 2k image from a 4k one, and they're all going to look different. If you master the 2k yourself, you're putting that choice in your hands, rather than throwing it to some other piece of gear that you may or may not have tested....

Graeme

[Axel Mertes]

Hello,

I'm mastering a short shot @ 5k and finished in 4k, and was wondering if a properly downscaled 2k DCP would hold better resolution than a 4k DCP if it's aimed at a 2k projector?

There will also be some 4k projection in the near future, so an only 2k DCP is not the plan.

As I understand, modern server can handle 4k DCP without problems and scale them to 2k for the 2k projector, but I wonder if the downscaling is made by pixel skipping or is it a hardware downscale and if it's good enough?

Any input would be appreciated. It will determine if we will have to make both packages.

Thanks

Patrick

While the DCI specifically allows to combine several versions of content within a single DCP, such as 3D, 2D, Trailers etc. I would not recommend doing so. Its better to have a true 2K and a true 4K DCP as individual file sets.
The point is that these large complete DCPs are so giant that they need ages to copy to the servers and use way more diskspace than is desireable.

Btw, our FinalDCP software can create a DCP directly from RED footage. A new build, schedule for before IBC, will allow scaling & scropping too. We do support RED Color 3 etc. and native R3D files and clearly RMD files too (beside many other formats such as ProRes, DNxHD, CineForm etc.). Thats a great option for dailies when you have a DCI theater "at hand".

You may try out our FREE Edition:

http://www.magnamana.com/products/

Cheers,
Axel

[Marc Wielage]

SimpleDCP, IndieDCP, Fotokem, and Quvis all have good resources on their websites as to how to prep files for creating DCPs. They can give you the pros and cons of coming from a 4K source vs. from a 2K source.

My personal opinion is that it makes more sense to hire an outside company to do your DCP deliverables for you, simply because they'll have DCP-compliant servers and projectors that will let you see exactly how it will look in an actual theater. I would not try to make a DCP myself using only a computer display, because of the difficulties in optimizing the display for XYZ color space.

If you have a digital projector and screening room with 5.1 surround, then it would just be a question of verifying the file and calibrating the projector for D-Cinema colorspace, which can be done. But I'd also worry about audio sync, audio channel assignments, and Q/C-ing the entire project to make sure that every frame and every pixel is perfect.

[Danko Dolch]

Hi,

why not just master a 4K DCP version?

I don't know of any problems with playing back 4K Interop DCP's on 2K DCinema systems. The picture quality was fine on screen all the time for me.
(Lot's of projectionist's got in panic in the past because they don't know they can play the 4K package on their 2K DCinema system - some special ECinmea servers needed software updates because the 4K DCP had stuttering playback first)

If you master a 2K DCP you will want a additional 4K DCP for future screenings - resulting in higher cost.

If you send a 2K DCP to a 4K cinema they will be disappointed. If you send both 2K & 4K DCP you have higher distribution cost.


I don't see a reason in not using the DCP system as designed - and that means 4K content is mastered in 4K resolution and played back in 2K on legacy equipment. (Oh sorry - 2K legacy - couldn't resist - this the the "RED 4K cinema" forum right ;-)

@Graeme: Do you have real concerns that the 2K decoding sheme for 4K content isn't propperly handled on current 2K DCinema systems? Thanks to CineLink encryption I don't checked the output under lab conditions...

[Patrick Tresch]

@Graeme: Do you have real concerns that the 2K decoding sheme for 4K content isn't propperly handled on current 2K DCinema systems? Thanks to CineLink encryption I don't checked the output under lab conditions...

I was also wondering, as I thought JPEG2000 was wavelet and it could use 1/2 the resolution from the 4k container : read 2k from the 4k file by skipping the unnecessary pixels. Doing this without the need of downscaling the 4k.

?

Pat

[Danko Dolch]

... use 1/2 the resolution from the 4k container : read 2k from the 4k file by skipping the unnecessary pixels. Doing this without the need of downscaling the 4k.
Pat

exactly - thats the way the decoding process is working... in easyDCP Player + this works flawless can switch back to 2K 1K... perfect image quality...

[Axel Mertes]

exactly - thats the way the decoding process is working... in easyDCP Player + this works flawless can switch back to 2K 1K... perfect image quality...

Hi Danko,

while you are correct that one can play a 2K DCP from any 4K DCP stream on any player is valid, I have to disagree with your recommendation.

There are two reasons why some may still decide to make a seperate 2K DCP:

1. Data rate for 2K is typically higher.
A 4K DCP is quite often done at 250 MBit/s. That is for four times the picture data of the 2K signal. In turn that means you average on 1/4th of 250 MBit/s, so roughly 67.5 MBit/s per 2K quarter. 67.5 MBit is quite poor level for 2K DCPs. Most of the encoding systems default to ~125 MBit/s for 2K content, which is double the data rate your 2K strip from a 4K DCP might contain. However, this is not exactly true, as we would need to check the data rate of each of the resolution levels to see if we have really so much data in the last 2 wavelet layers above 2K to create the 4K. But from what I can tell, it must be close, because its the final detail level.

I have not even brought up the arguement one might decide to make a true 2K 250 MBit/s DCP. That will look significantly better than the 2K strip out from the 4K DCP...

2. DCP size and copying time.
The 4K DCP is typically 250 MBit/s is about 2 GByte/min. Over normal USB2.0 this copies at roughly 1 GByte/min, so it takes twice as long to copy the DCP than its runtime. And again, a 4K DCP on a 2K only server will not look better, see above.
The good 2K DCP at 125 MBit/s will copy from USB2.0 in about the playback time, so in half the time of the 4K DCP. Further, it will have nearly double the data rate per pixel on screen in a 2K playback scenario.

One should always think twice!

There IS a quality difference between a native 2K DCP and a 2K strip from a 4K DCP, due to the bandwidth involved.

Cheers,
Axel