Cutsio Blog

ARRIRAW .arx workflow: How to handle legacy HDE sequences in post

ARRIRAW/HDE .arx is a legacy CODEX HDE format, not a current Alexa 35 recording format. How it differs from .ari and MXF-wrapped ARRIRAW, and what to verify before cloud upload or DaVinci Resolve conform.

What is ARRIRAW/HDE .arx and how does it differ from other ARRIRAW formats?

ARRIRAW/HDE .arx is a legacy CODEX High Density Encoding workflow for ARRIRAW frame sequences, not a new in-camera ALEXA 35 recording format. ARRI documents .arx as HDE-encoded ARRIRAW frame sequences used for earlier camera models, while current ALEXA 35, ALEXA 35 Xtreme, and ALEXA 265 HDE workflows use MXF/HDE output from CODEX Device Manager or the ARRIRAW HDE Transcoder.

The ARRIRAW family includes legacy .ari single-frame sequences, MXF-wrapped ARRIRAW, legacy .arx HDE frame sequences, and newer MXF/HDE files. Each serves a different workflow need and has different software support.

The practical takeaway: if .arx appears in a conform package, treat it as legacy HDE ARRIRAW and verify decoder support immediately. For ALEXA 35-class productions, expect MXF/ARRIRAW or MXF/HDE rather than .arx frame sequences.

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When should you use .arx instead of .mxf ARRIRAW?

For new productions, .arx is usually not a format you choose on ALEXA 35-class cameras. It is more often something a post team receives from a legacy ARRIRAW/HDE workflow. The choice is normally between MXF/ARRIRAW, MXF/HDE, ARRICORE, or ProRes depending on the camera and post path.

Use .arx only when:

• The footage already comes from a legacy CODEX HDE .arx workflow
• The post software stack has been verified to support .arx decoding
• The DIT report and checksum manifest confirm the frame sequence is complete
• The finishing vendor has tested a representative clip before conform

Use MXF/HDE or MXF/ARRIRAW instead when:

• The post house has not verified .arx support in its NLE and grading software
• The production requires maximum compatibility across different post vendors
• The conform workflow uses third-party tools that may not support .arx
• The production is shooting on ALEXA 35, ALEXA 35 Xtreme, or ALEXA 265, where current HDE is MXF-based

What are the known compatibility issues with .arx in post production?

The .arx format has specific compatibility limitations that must be verified before production begins.

The most important limitation: .arx support requires software that can decode CODEX HDE ARRIRAW frame sequences. Newer tools may focus on MXF/ARRIRAW and MXF/HDE instead, so support must be verified instead of assumed.

If a post application does not support .arx, test conversion through ARRI Reference Tool or another ARRI-supported workflow before editorial starts. Do not assume a transcode will preserve every metadata field until it has been checked.

For cloud dailies workflows, verify that the dailies platform supports the exact .arx package before transfer. In Cutsio, use approved ProRes review media for indexing and playback while the .arx sequence remains in the production's conform workflow.

How does .arx compare to HDE-compressed .mxf ARRIRAW?

.arx is an HDE ARRIRAW sequence workflow. The comparison that matters for current productions is legacy .arx HDE sequences versus MXF/HDE files.

The practical difference: .arx sequences need sequence-aware handling, while MXF/HDE behaves more like the current MXF camera-original workflow. MXF/HDE is the safer choice for new ALEXA 35-class productions.

For productions that want storage savings and maximum post compatibility, the recommended workflow is to record .mxf ARRIRAW in-camera and apply HDE during offload. This gives the 40% storage reduction with full NLE compatibility.

How does Cutsio handle .arx files in the enterprise ingestion pipeline?

Cutsio should be evaluated with a representative .arx sequence and its approved ProRes review media before production relies on the workflow. Keep the .arx original available for conform and finishing.

The upload workflow:

1. DIT offloads .arx files from Alexa 35 Compact Drives
2. The .arx files are uploaded to Cutsio through the enterprise add-on
3. Cutsio verifies decode support for the uploaded .arx package
4. Streamable review assets are generated with the correct LogC-to-video color transform
5. The original .arx files remain attached for download and conform
6. Visual Intelligence indexes the generated review stream

The online editor downloads the original .arx files for conform. If the NLE supports .arx natively, the files are imported directly. If the NLE does not support .arx, the editor can download the files and transcode to ProRes or DNxHR using the ARRI Reference Tool.

How do you verify .arx support before production?

Before committing to .arx as the acquisition format, run a compatibility test through the entire post pipeline.

Test checklist:

1. Confirm whether the job is receiving legacy .arx HDE sequences or current MXF/HDE files
2. Offload or restore the complete sequence/package using the production copy tool
3. Open the .arx sequence or MXF/HDE file in ARRI Reference Tool to verify it decodes correctly
4. Import the sample into DaVinci Resolve, Avid Media Composer, Adobe Premiere Pro, or the actual finishing software
5. Verify that the color space, look metadata, and timecode are read correctly
6. Upload the sample package to Cutsio and verify the review stream
7. Download the package from Cutsio and verify the conform package
8. If any step fails, switch to MXF/ARRIRAW or MXF/HDE for new material where possible

FAQ

Is .arx visually lossless or mathematically lossless?

.arx is an HDE ARRIRAW sequence format. HDE is ARRI/CODEX's lossless path for reducing ARRIRAW storage; verify the exact file type and tool support before calling the workflow approved.

Can .arx files be converted to .mxf ARRIRAW in post?

Use the current ARRI Reference Tool documentation to confirm available conversions for the exact .arx sample. Do not assume conversion support until the finishing vendor has tested it.

Does .arx preserve ALF4 look metadata?

Verify this with the actual sequence. Legacy .arx workflows can carry ARRIRAW metadata, but look-package behavior should be checked against ARRI Reference Tool output and the approved dailies reference.

Which Alexa 35 recording modes support .arx?

ALEXA 35-class HDE workflows are MXF-based. ARRI documents .arx HDE frame sequences as a legacy path for earlier camera models, while ALEXA 35, ALEXA 35 Xtreme, and ALEXA 265 use MXF/ARRIRAW and MXF/HDE workflows.

Should I use .arx or HDE for cloud dailies?

For current ALEXA 35-class cloud dailies, use MXF/ARRIRAW or MXF/HDE unless the production has a specific legacy .arx package to ingest. Use .arx only if the entire post pipeline has been verified to support it.