rExif / docs / formats-and-sidecars

Supported Formats and XMP Sidecars

Non-destructive in-place writing, video atom handling without re-encoding, and Adobe XMP sidecars for RAW photos.

Non-Destructive In-Place Writing

Modifying file metadata must never compromise the underlying optical quality of photographs or video recordings. Conventional tools frequently decompress and re-encode images, producing permanent generation loss and compression artifacts.

rExif operates directly at the container header level, avoiding any re-encoding steps.

Raster Image Formats (In-Place Updates)

For standard raster images, rExif modifies exclusively the dedicated metadata chunks:

  • JPEG / JPG: Rewrites binary markers APP1 (EXIF), APP2 (ICC Profile), and APP13 (IPTC/Photoshop). Pixel arrays remain bit-for-bit identical to the originals.
  • HEIC / HEIF (Apple): Navigates the ISOBMFF container structure, updating the meta and iloc boxes without recompressing HEVC-encoded video frames.
  • PNG: Manages native eXIf, tEXt, zTXt, and iTXt chunks.
  • TIFF: Updates Image File Directories (IFD) while preserving full 16-bit or 32-bit color fidelity.

Video Containers (QuickTime & MP4)

Modern video files store temporal metadata inside container atom trees:

  • MOV, MP4, M4V: rExif traverses the QuickTime atom hierarchy (moov $\rightarrow$ mvhd and trak $\rightarrow$ mdia $\rightarrow$ mdhd).
  • When adjusting capture timestamps, 32-bit and 64-bit timestamps within the mvhd atom are updated in place with zero video or audio transcoding. The process is instantaneous even for 50 GB ProRes 422 or 8K HEVC recordings.

RAW Camera Formats and Sidecar .xmp Files

Proprietary RAW files produced by professional cameras hold un-demosaiced sensor data:

  • Canon: .CR2, .CR3
  • Nikon: .NEF, .NRW
  • Sony: .ARW
  • Fujifilm: .RAF
  • Olympus / OM System: .ORF
  • Panasonic: .RW2
  • Adobe Digital Negative: .DNG

[!NOTE] To preserve the forensic integrity of the camera capture, rExif leaves RAW binary files unaltered. Instead, it creates industry-standard Adobe XMP Sidecars:

  • Changes to dates, GPS coordinates, copyright, keywords, and star ratings are stored in an adjacent XML file with the .xmp extension (e.g. _DSC0012.ARW.xmp or _DSC0012.xmp).
  • The sidecar file is natively detected and prioritized by Adobe Lightroom Classic, Adobe Camera Raw, Bridge, Capture One, and Darktable.

Broadcast Video Containers (AVI, MKV, MTS)

For broadcast and legacy video formats such as AVCHD (.mts, .m2ts), Matroska (.mkv), and AVI, rExif generates companion .xmp sidecars recognized by non-linear editing suites like Adobe Premiere Pro and DaVinci Resolve.