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Image MIME Reference
HEIF-Sequence

High Efficiency Image File Format Sequence

image/heif-sequence
VS

Silicon Graphics Image

image/x-rgb
SGI-RGB

A complete technical comparison of High Efficiency Image File Format Sequence and Silicon Graphics Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature HEIF-Sequence SGI-RGB
Transparency (Alpha) Yes Yes
Animation Support Yes ✕ No
Progressive Loading ✕ No ✕ No
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
High Efficiency Image File Format Sequence
image/heif-sequence
Extension
.heifs.heif.hif
Container HEIF / ISOBMFF (ISO/IEC 14496-12)
Compression Lossy / Lossless
Algorithm
Codec Agnostic (HEVC, AVC, JPEG, AV1)
Color Depth 8-bit, 10-bit, 12-bit, 16-bit
Developed by Moving Picture Experts Group (MPEG)
Released 2015
Magic Bytes
XX XX XX XX 66 74 79 70 6D 73 66 31
Full HEIF-Sequence reference →
Silicon Graphics Image
image/x-rgb
Extension
.rgb.sgi.rgba.bw.int.inta
Container SGI Image Header (512 bytes)
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneScanline RLE
Color Depth 8-bit (Per Channel), 16-bit (Per Channel)
Developed by Silicon Graphics, Inc. (Paul Haeberli)
Released 1988
Magic Bytes
01 DA
Full SGI-RGB reference →

Browser Support Comparison

Browser HEIF-Sequence SGI-RGB
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
HEIF-Sequence

HEIF-Sequence Strengths

  • Codec-agnostic container allows for extreme flexibility when storing multi-frame photographic data
  • Maintains the space-saving benefits of ISOBMFF shared frame data blocks
  • Excellent for archiving computational photography workloads like exposure brackets or focal stacks
Limitations
  • Codec ambiguity means a decoder might be able to parse the container but fail to decode the underlying pixels
  • Zero native web browser support
  • Complex container structure requires specialized parsing libraries to extract individual frames
SGI-RGB

SGI-RGB Strengths

  • Supports 16-bit precision per channel and an embedded alpha channel, making it ideal for the demanding compositing workflows of 1990s cinema VFX
  • The scanline-based RLE compression was exceptionally fast to decode on classic MIPS-based SGI workstations
  • Features a straightforward 512-byte header, making it relatively easy to parse and write custom decoders in C or Python
Limitations
  • Completely obsolete and unsupported in modern web environments
  • Replaced entirely by TIFF, OpenEXR, and PNG in modern visual effects and 3D rendering pipelines
  • Lacks support for modern color management via ICC profiles or advanced EXIF metadata

When to choose which format

HEIF-Sequence
Use HEIF-Sequence when…
  • Burst Photography
  • Focal Stacking
  • Exposure Bracketing
  • Time-Lapse Data
SGI-RGB
Use SGI-RGB when…
  • Legacy 3D Animation and VFX Textures
  • Silicon Graphics IRIX Workstation Archival
  • 1990s Medical Imaging

More comparisons

HEIF-Sequence vs ACES → SGI-RGB vs ACES → HEIF-Sequence vs APNG → SGI-RGB vs APNG → HEIF-Sequence vs AVCI → SGI-RGB vs AVCI → HEIF-Sequence vs AVCS → SGI-RGB vs AVCS → HEIF-Sequence vs AVIF → SGI-RGB vs AVIF → All comparisons →
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