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ARRIRAW

uncompressed, unencrypted and uncompromised

About ARRIRAW

ARRIRAW is ARRI’s format for uncompressed, unencrypted and uncompromised sensor data. It can be considered a digital version of the camera negative. ARRIRAW is the only format that retains the camera's natural color response and great exposure latitude as uncompressed and unprocessed sensor data.

Like film negative, ARRIRAW data has to be developed – or rather processed – in order to convert the single channel image, which represents the raw Bayer pattern sensor readout, into a color image suitable for normal viewing. The originally recorded raw data remains pristine, always providing the flexibility to go back and refine the results. This makes ARRIRAW the perfect format for digital cinematography and high quality visual effects production.

Our camera line-up supports in-camera recording of ARRIRAW or MXF/ARRIRAW data. MXF/ARRIRAW is ARRIRAW within a container format (*.mxf), hence one clip is only one file as opposed to some thousand files with every file being a single frame in the regular ARRIRAW format *.ari.

Older ALEXA cameras (ALEXA Classic, ALEXA Plus/Plus 4:3, ALEXA-M and ALEXA Studio) require an ARRI-certified external recorder which understands the T-Link signal.


ARRIRAW Processing

ARRI has built long-term relationships with postproduction equipment manufacturers through the ARRI Partner Program. These relationships have facilitated all of the leading compositing and color correction tools to be enabled with direct processing of the ARRIRAW file format.

In addition, ARRI offers a software development kit (SDK) for ARRIRAW processing, containing documentation of the ARRIRAW processing pipeline and a library – executable code – that the vendor can incorporate into their application. ARRI also supports vendors who wish to implement the ARRIRAW processing procedure on their own, through comprehensive documentation of a three-phase color processing pipeline and continuous direct support.

De-Bayering
The first phase of ARRIRAW processing is the most compute-intensive. ARRIRAW images (like all camera raw images) have only one ‘color’ channel (in fact it’s a color-coded luminance channel). A color reconstruction algorithm calculates the missing components for each pixel based on the type and position of colored filters on the camera sensor. ARRI cameras use the Bayer pattern color filter array. The term 'color reconstruction' therefore is also known as ‘de-bayering’. The Bayer pattern filters the light hitting the sensor so that 50% of the sensor’s photosites are used to represent green, 25% of the photosites represent red and the remaining 25% represent blue.  

The image above shows a single-channel capture from the sensor on the left and on the right the reconstructed image facilitating the color filter array. Half of the reconstructed image's green values are interpolated from the surrounding photosites rather than captured, as are three-quarters of the red and three-quarters of the blue.
The output quality of the image depends on the de-bayering algorithm. Generally speaking, a simpler algorithm will process faster, but also involve a higher probability for color errors.

For VFX, however, the images often are processed using the native sensor pixel count and then downscaled to e.g. 4K or 2K at a later stage. Using this approach takes advantage of the luminance resolution, which correlates to the sensor pixel count.

ARRIRAW SDK and 3rd Party Implementations
In many cases, ARRI's SDK is fast and adaptable enough to satisfy the processing needs of an application. But in some cases, especially when the product uses custom hardware (or standard hardware in a nonstandard way), partner program members may want to implement the ARRIRAW processing pipeline themselves. In this scenario, the SDK serves as a reference against which the partner program member's developers can test their results before submitting evaluation imagery to ARRI's workflow group. In a few applications, the vendor's product offers both processing solutions, giving the user the option of maximum throughput with a very good match to the SDK, or bit-for-bit matching of other products that use the reference SDK implementation.

Variances and Tolerances
When the ARRIRAW processing pipeline has been implemented into a product, a company submits the image processing results to ARRI. Our engineers then evaluate the images based on a standardized set of tests. The test must produce completely satisfactory results for us to issue the "Certified for ARRIRAW Processing" label for this product.

ARRI allows partner program members some variation in the implementation of the first (de-bayering) phase of the processing chain. However, there are no compromises allowed during the second and third phases of the processing chain where Log C or video encoding is completed. The reason for the flexibility in de-bayering is that some platform vendors traditionally produce a ‘softer’ image as a result of their de-bayering process. These platforms might choose to perform a sharpening operation after the conversion from ARRIRAW to the desired working format. ARRI will certify a product’s default settings, even when producing de-bayered images that are less sharp than the SDK reference, under one condition: the product must provide settings that render the converted image to match the SDK reference, free from artifacts and matching in geometry, tonal balance, color rendition, bit depth and metadata.


ARRIRAW Converter

The ARRIRAW Converter (ARC) application provides a graphical user interface for ARRI’s reference SDK. In addition to the GUI version of ARRIRAW converter, a command-line tool (CMD) for processing images or image sequences is available for Mac OS X, Windows and various distributions of Linux.

You can download your copy of ARC here.


Testing Your Workflow
ARRI recommends running tests to define:

  • How the intended look can be achieved using the chosen toolset(s).
  • The different tools that need to be set up to meet the production's expectations of consistent results.
  • The settings required for a chosen tool to most closely match the SDK reference results, if no other reference set of results are available.

You can use an ARRIRAW frame grab as test material. ARRI provides sample footage shot with our cameras on FTP server and Webgate..