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@Eric Hanson - 4K dpx files

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Bob Zelin
@Eric Hanson - 4K dpx files
on Mar 14, 2013 at 1:15:02 pm

Hi -
I know that we will speak later today, but in case I am wrong - even in my research, I wanted to post this - specifically to see if Facilis will state what their max bandwidth is with 16Gig Fibre using the new ATTO cards.

4k dpx files - to play out in REAL TIME - is too fast for any modern shared storage system (maybe not with 16Gig Fibre) - typical 10gig bandwidth is about 400MB/sec, which is not fast enough - and it's my opinion that you are not going to be able to get a shared storage solution for ALL of your workstations to do 4k dpx finishing. It's too much bandwidth for them all to be working at the same time.

copied from a RED User forum between Rob Lohman and Lucas Wilson (two smart guys) -
Hi Rob...

Are you talking about RAW or DPX? I may be misunderstanding something (entirely possible...,) but take a look.

4096 * 2304 = 9,437,184 (number of pixels in the file)

9,437,184 * 32 = 301,989,888 (number of bits in the file - each pixel = 32 bits in a 10-bit DPX file)

301,989,888 / 8 = 37,748,736 (number of bytes in the file)

37,748,736 / 1,048,576 = 36 (number of megabytes in the file)

So each 4096*2304 10-bit DPX = 36 MB/frame.

36 * 24 = 864

So realtime playback of that 10-bit DPX sequence would need 864 MB/s.

Cheers,

Lucas
-----
ASSIMILATE, Inc.
Los Angeles

Bob Zelin



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Sareesh Sudhakaran
Re: @Eric Hanson - 4K dpx files
on Mar 15, 2013 at 8:56:32 am

It doesn't invalidate anything you're saying, but I think the calculation is incorrect.

4096 x 2304 = 9,437,184 pixels

Color Bit Depth per pixel = 10 bits per channel
Channels = 3 (RGB) channels (If there is an alpha channel or more, like OpenEXR, then you'll need to multiply)
Total Color Bit Depth per pixel (across all channels) = 10 x 3 = 30

Total bits = 30 x 9,437,184 = 283,115,520 bits = 35,389,440 bytes = 33.75 MB per frame.

On top of this, you have to account for metadata for DPX, which is not a lot if you're only calculating data rate.

@24fps, Data Rate = 33.75 x 24 = 810 MB/s.

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Alex Gerulaitis
Re: @Eric Hanson - 4K dpx files
on Mar 15, 2013 at 12:25:43 pm

Good point about image headers and metadata, Sareesh.

Most "unpacked" file formats (if not all) that don't evenly fit with 8-bit boundaries, are "padded" to those boundaries, i.e. there's a good possibility a 30-bit (3x 10-bit) DPX pixel does take 32 bits.


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James McKenna
Re: @Eric Hanson - 4K dpx files
on Mar 17, 2013 at 6:34:39 pm

Bob,

Funny enough at the time you were writing this we were on our way to an event in NY to show 4K playback (among other things) at the Digital Arts theater on West 29th. (tinyurl.com/FacilisNY3-14)

Sharif from Assimilate can attest to the fact that no SAN has been as successful out of the box than TerraBlock with 4K playback. We can do it on a single enclosure, and without getting into all of the various frame sizes and bit depths, it's even possible to do on a Multi-user Write volume over 10Gb Ethernet or 16Gb fibre. The larger frame formats, all the way up to 16bit, will require Single-user Write over 16Gb.

4K compatibility with RAW and uncompressed formats, and our unique ability to support these workflows, is a focus at NAB for us this year.

Jim McKenna
Facilis Technology
978-562-7022 x101


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Eric Hansen
Re: @Eric Hanson - 4K dpx files
on Mar 22, 2013 at 7:27:34 pm

hey Bob

As we discussed later that day, I wasn't trying to do 4k DPX at every client station. We'd like to have the ability to do compressed 4k workflows (such as RED) at each client station, and then finish on a 4k Linux Resolve. I would like this finishing station to have to ability *locally* to do 4k DPX. how much we'll be working in DPX, i'm not sure.

most likely, the client stations will stick to 1080 offline workflows and we'll do a 4k online in the Resolve suite.

Jim, i can't wait to check out your booth at NAB!

e

Eric Hansen
Production Workflow Designer / Consultant / Colorist / DIT
http://www.erichansen.tv


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