FORMAT



Autor: Redaktion


ARRIRAW

The RAW format of the Arri Alexa camera family.

ARRIRAW is the RAW format of the Arri Alexa camera family. With the introduction of the XR module, Arri have made it possible to record ARRIRAW footage onto an XR Capture Drive. It is also possible to record RAW via HD-SDI onto external recorders, however it should be noted that ALEXA Classic cameras (with the SxS module) cannot record ARRIRAW internally and use a special protocol called T-Link, to output ARRIRAW via HD-SDI.

Like other raw formats, ARRIRAW is comprised of the data output of the image sensor of a digital camera with minimal processing. The recorded data is often referred to as a ‘digital negative’. RAW images are then taken through an ‘image development’ process and converted into a variety of file formats for storage and manipulation. In this context, the process of converting RAW recordings into viewable images involves debayering, the adjustment of  parameters such as white balance, noise reduction, colour space, or sensor sensitivity as part of the post production process. Because these settings are metadata only, the process is completely non-destructive.

To convert ARRIRAW into true RGB data, ARRI offers the ARRIRaw Converter tool. A variety of external software solutions that can process ARRIRAW natively can be found in the table below.

To process ARRIRAW in real time (eg, for quality check on the set), performance systems with a minimum throughput of 230MB/s and high performance graphics card with OpenCL or CUDA support are strongly recommended.

The main advantage of ARRIRAW over a ProRes 4444 format is its ability to manage poor lighting conditions or for use when the material requires heavy colour correction or visual effects work. Under these circumstances, you can see compression artefacts in ProRes encoded material, while ARRIRAW stays clean.

The resolution of an ARRIRAW frame differs based on a number of factors. In 16:9, a frame corresponds to 2880x1620 pixels. In 4:3, the frame corresponds to 2880x2160 pixels. If you turn up the "Open Gate", 3414x2198 pixels per frame are stored. The aspect ratio of 16:9 is basically the standard. 4:3 is used for anamorphic images or visual effects. Similarly, the maxiumum frame rate differs depending on the sensor mode. In 16:9, the Alexa XT achieves 120fps and 75fps in "Open Gate"). In 4:3, it achieves 90 fps. Classic Alexa models have a reduced output with 60fps in 16:9 and 48fps in 4:3.

All metadata generated by the camera is stored in the file headers of the ARRIRAW file and can be read with the ARRIRAW Converter or the command line tool ARRI Meta Extract for further processing. The ARRIRAW format does not create additional sidecar files.

ARRIRAW is very demanding in terms of the management of the resulting file sizes as well as the necessary processing power to playback, convert or manipulate the video. However, this format offers tremendous opportunities in the post-production of high-quality images shot under demanding conditions.

ARRIRAW Summary

  • VIDEO
  • Quantising: 12-bit
  • Chroma-Subsampling: 4:4:4
  • Datarate:
  • 16:9 ARRIRAW: 1.34Gb/s (approx. 168MB/s) or about 605GB per hour
  • 4:3 ARRIRAW: 1.79Gb/s (approx. 224MB/s) or about 806GB per hour
  • Codec: uncompressed
  • Resolution:
  • 16:9 = 2280 x 1620
  • 4:3  = 2280 x 2160
  • cropped 4:3 = 2578 x 2160
  • open gate 4:3 = 3414 x 2198
  • Framerate:
  • Alexa XT 16:9 >120 fps
  • Alexa XT 4:4 >90 fps
  • Alexa XT 4:3 Open Gate > 75fps
  • Classic Alexa 16:9 with external recording device >60 fps
  • Classic Alexa 4:3 with external recording device >48 fps                                                                                 
  • SOFTWARE
  • Adobe Premiere Pro Speedgrade from CS6 onwards
  • Assimilate Scratch from v6.1 onwards
  • Blackmagic Design Resolve from v9.1.6 onwards
  • Colorfront OSD
  • Digital Vision Nucoda Filmmaster from v2011_0 onwards
  • Quantel Pablo
  • The Foundary Nuke
  • RECORDING MEDIA
  • File Format: .ari file structures
  • Recording Media: All Alexas with XR modules can record onto "XR Capture Devices" (dedicated SSDs)
  • any "Alexa Arriraw T-Link"-capable recorders
  • Codex Digital Onboard S & M
  • S.Two OB- 1
  • Astrodesign HD - 7502-
  • Convergent Design Gemini
  • cineFlow cine Take
  • Recording Duration / Capacity: XR Capture Devices at 24fps: 47min (16:9), 35min (4:3), for external recorders dependent on recording media

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