This IS the Avid L2: Re: [Avid-L2] raw 4K from Canon c300?

Sunday, June 29, 2014

Re: [Avid-L2] raw 4K from Canon c300?

Hi Rupert,

You can find an explanation of their 4k and 2k RAW signal in this Canon white paper:

http://learn.usa.canon.com/app/pdfs/white_papers/White_Paper_originatinghighqualityc500.pdf

Excerpts from the document:

"...unlike the traditional approach to reading out from such a single image sensor via singular RAW date stream that contains the encoded RGB information, the Canon image sensor uses four parallel readouts to deliver that RAW data as four separate 2K (or HD) data streams… These four real-time video components carry all of the color information originated by the 4K Bayer CFA – and they are then delivered from the image sensor to the camera digital processor – for both 4K and 2K origination."

"When the C500 is originating 4K these four high bit-depth R, Gr, Gb, B components are logarithmically encoded to 10-bit and then formulated into a RAW Clip Structure (termed .rmf files – that combines the RAW video files with the digital audio files, metadata, and clip management files)… The clips are then multiplexed to form a single serial RAW Component Data Transport Interface – in accordance with the SMPTE 3G SDI serial 3G SDI interface (ST 425-1:2011). Construction of the final 4K RGB components requires downstream debayering to build up the separate three 4K RGB frames."

"...the RAW data rate output is constrained to less than 3Gbps for both 4K and 2K having frame rates up to 30P – so only one 3G SDI interface would be required.

This data rate was achieved without resorting to compression by constraining the camera output to a bit depth of 10-bit for the 4K RAW and to 12-bit for the 2K RAW – as outlined in the following:

Canon 4K: 4444 Bayer RAW Data rate @ 30 fps
2048 x 1080 x 4 x 10 x 30 = 2,654,208,000 bits/ second

Canon 2K: RGB 4:4:4@12 -bit Data Rate at 30 fps
2048 x 1080 x 3 x 12 x 30 = 2,388,787,200 bits / second

Both of these data streams fit comfortably within the 3G SDI interface standard. For higher frame rates – up to 60P – the elevated data rates (still less than 6 Gbps) will require two 3G SDI interfaces.

To meet those two bit-depth constraints without compromising restoration of the higher bit-depth of the image sensor output in postproduction resort was made to an alternative bit rate reduction strategy – namely, logarithmic encoding of the image sensor linear representation (according to the mathematically prescribed Canon Log). Specifically, the high bit depth of the image sensor digital outputs are logarithmically transformed to a 10-bit depth for the 4K mode, and to a 12-bit (with 10-bit as a selectable option) for the 2K mode. This is a completely reversible process. While Canon does not disclose the bit depth of our A/D converter – we do affirm that the linearization process (de-Canon Log) can reproduce the linear representation at 12-bit, 14-bit, or 16-bit (DPX or Open EXR)."

ferenc

2014.06.29. dátummal, 13:40 időpontban Rupert Watson rupert@root6.com [Avid-L2] <Avid-L2@yahoogroups.com> írta:

Thanks for the information. Do you know what the data rate off disk of the c500 raw files is ?

Rupert Watson
www.root6.com
+44 7787 554801

On 28 Jun 2014, at 12:11, Koscso Ferenc ferenc.koscso@penna-media.hu [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

Hi Rupert,

you probably meant C500? C300 can not shoot in 4k. It has 4k sensor, but can record and output HD only.

ferenc

2014.06.28. dátummal, 11:03 időpontban Rupert Watson rupert@root6.com [Avid-L2] <Avid-L2@yahoogroups.com> írta:

Has anyone got experience of working with raw 4K from Canon c300?

If you have, can you tell me what the real world data rate off disk is?

Rupert Watson
www.root6.com
+44 7787 554801

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