How to process RAW from 4k Micro Studio Camera?
The Blackmagic Micro Studio Camera 4K is a compact Ultra HD camera designed for live productions. It features the same image sensor as in Blackmagic's Studio Camera 4K, which supports 3840 x 2160p video up to 30 fps and 1080p video up to 60 fps. The camera is equipped with an active MFT mount that can accept native MFT lens or be adapted to a wide range of other modern and vintage lenses, including B4 lenses. It outputs 10-bit 4:2:2 video via 6G-SDI and can be remotely controlled from an ATEM switcher using SDI control protocol. The camera packs many professional studio features into a compact form factor, including a built-in color corrector, talkback, tally indicator, PTZ control output, and B4 lens control output.
Resolution and bit depth
The resolution of the RAW frame is 3872 pixels x 2192 lines, which includes a border that surrounds the image data. Most users discard this border after debayering, as it can contain image artifacts on the outer edges. The RAW data at pixel number 16 inside the horizontal and vertical corners will therefore correspond with the corner of the Ultra HD frame when the camera is outputting 3840 x 2160 in the non RAW mode. Bit depth of each pixel will be 12 bits. That camera doesn’t have 4K internal recording, so you need to utilize external BMD framegrabber which supports 6G-SDI, like DeckLink. There is also possibility to utilize special external SSD with SDI interface to record raw data directly to SSD.
RAW recording from Micro Studio 4k
One can record the uncompressed 12-bit RAW signal as an QuickTime MOV file with Blackmagic HyperDeck Studio Pro or any device capable of 10-bit SDI uncompressed recording or capture. Once you have a QuickTime recording of the RAW data (this is actually 12-bit SDI RAW in MOV container), you will need to unpack RAW pixels from MOV to perform your own debayering and other processing of the image data from the sensor. The RAW frame is packed into the active picture area of a standard UHD 422 SDI frame.
If the camera outputs 12-bit RAW data over SDI, then user has to do debayering according to bayer pattern which is GRBG for that camera. RAW pixels are packed and transferred according to SDI standard.
Here we can try to answer to the following question: How to accomplish fast preview for RAW footages from that Blackmagic camera? User can record 12-bit RAW SDI into MOV file and save it to SSD. We've implemented the software which can unpack MOV file with 12-bit RAW SDI data, add DCP profile and White Point to the current MOV and process all frames on GPU in realtime at frame rate 25 fps. This is actually fast RAW SDI processor for Blackmagic Micro Studio Camera 4K. Now this is the feature of PRO version of Fast CinemaDNG Processor software, which is a must for high performance culling, trimming and previewing. And it's working on NVIDIA GPU, so it offers just incredible speed. Fast CinemaDNG Processor software dramatically increases responsiveness. Everything is working very fast on good CPU/GPU/SSD.
Apart from RAW SDI Processor we've also implemented RAW SDI Converter which is capable to convert 12-bit RAW SDI MOV file to DNG series with or without compression. This is also a new feature of PRO version of Fast CinemaDNG Processor software.
What's the difference between RAW SDI and in-camera processed 4:2:2?
There are actually two choices to work with Blackmagic Micro Studio 4K camera:
- to process RAW data inside the camera, to send 4:2:2 color data via SDI, then to compress data to ProRes at the external recorder
- to send 12-bit RAW SDI data from the camera to BMD framegrabber and then to PC or write it directly to external SSD with SDI connection
The first approach relies on in-camera processing (FPGA-based image processing), so one can't expect high quality from such a debayer. On captured images we can easily see demosaicing artifacts which are common for bilinear debayer algorithms. This is the reason why that mode of operation is not very good if you need to get high quality footage. This is very simple - to write processed data to external SSD, but there is a problem with image quality.
If we try to work with RAW data which is sent via SDI from camera to external SSD or to framegrabber, this is more complicated solution and we will need to apply our own debayering to get high quality color images at the output. At first we save RAW SDI stream to MOV container and we will work with MOV file further. We will parse and unpack RAW data and apply standard image processing pipeline to get good picture from each RAW frame. This is actually the same as we process DNG, but here we are working not with DNG, but with 12-bit RAW SDI. High quality debayer algorithm on GPU gives us both high quality and good performance, so we can process and play that MOV file in realtime. This is preferred approach to work with Blackmagic Micro Studio 4K camera.
How to process RAW SDI from Micro Studio Camera 4K
- Capture 12-bit RAW and send it over 10-bit SDI to PC or to external recorder
- Record MOV video file with 12-bit RAW SDI data
- Read MOV 12-bit RAW SDI data from SSD, import, parse, unpack
- Add DCP and White Point to process RAW frames
- Optional export to DNG
- White Balance and Demosaicing on GPU
- High performance denoising on GPU
- Realtime viewer and player with full image processing pipeline on GPU
- Undistortion with LCP profile
- Realtime grading with 3D LUTs (RBG and HSV)
- Export to jpg/tiff image series or to video
To accomplish that task, user needs software to extract and unpack 12-bit SDI RAW images from MOV and he also needs DCP profile and White Point, which one can get from captured image of Color Checker (6x4) and DCamProf software. Such a processing is also possible for multicamera system, user just need to calibrate each camera separately.