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Image MIME Reference
JPEG-XS-(HEIF)

JPEG XS Image (HEIF Container)

image/jxsi
VS

RealNetworks RealFlash

image/vnd.rn-realflash
RealFlash

A complete technical comparison of JPEG XS Image (HEIF Container) and RealNetworks RealFlash — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature JPEG-XS-(HEIF) RealFlash
Transparency (Alpha) Yes Yes
Animation Support ✕ No Yes
Progressive Loading ✕ No Yes
HDR Support Yes ✕ No
EXIF Metadata Yes ✕ No
ICC Color Profile Yes ✕ No
JPEG XS Image (HEIF Container)
image/jxsi
Extension
.jxsi.jxs.hif
Container HEIF / ISOBMFF (ISO/IEC 23008-12)
Compression Lossy (Visually Lossless) / Mathematically Lossless
Algorithm
JPEG XS (ISO/IEC 21122-1)
Color Depth 8-bit, 10-bit, 12-bit, 14-bit, 16-bit
Developed by Joint Photographic Experts Group (JPEG)
Released 2019
Magic Bytes
XX XX XX XX 66 74 79 70 6A 78 73 69
Full JPEG-XS-(HEIF) reference →
RealNetworks RealFlash
image/vnd.rn-realflash
Extension
Container RealMedia / SWF
Compression Vector (Flash) / RealAudio Compression
Algorithm
Macromedia Vector CompressionDeflate (Zlib)
Color Depth 8-bit, 24-bit, 32-bit
Developed by RealNetworks & Macromedia
Released 1997
Magic Bytes
46 57 53 (FWS - Standard Flash) or 2E 52 4D 46 (.RMF - RealMedia Container)
Full RealFlash reference →

Browser Support Comparison

Browser JPEG-XS-(HEIF) RealFlash
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
JPEG-XS-(HEIF)

JPEG-XS-(HEIF) Strengths

  • Provides sub-millisecond encoding and decoding latency while retaining visually lossless quality
  • Brings the extensive metadata, EXIF, XMP, and color-profiling capabilities of the HEIF container to JPEG XS
  • Allows grouping of multiple high-quality JPEG XS frames into a single collection file
Limitations
  • Zero web browser compatibility, limiting it entirely to professional and industrial hardware workflows
  • Extremely niche adoption compared to standard HEVC-based HEIC or raw JPEG XS codestreams
  • Requires custom parsing logic to extract the JPEG XS codestream from the HEIF boxes
RealFlash

RealFlash Strengths

  • Allowed complex, interactive vector animations to stream smoothly over 28.8k dial-up modems
  • Perfectly synchronized streaming audio with timeline-based animations, which was revolutionary in 1997
Limitations
  • Heavily reliant on proprietary browser plugins (RealPlayer), which were notoriously bloated
  • Completely obsolete and unsupported on the modern web
  • Tightly coupled server-client architecture required expensive RealServer licenses to host

When to choose which format

JPEG-XS-(HEIF)
Use JPEG-XS-(HEIF) when…
  • Live Broadcast Infrastructure
  • Medical Imaging & Archival
  • Video over IP Networks
  • Automotive & Drone Systems
RealFlash
Use RealFlash when…
  • Historical Dial-up Web Animation
  • Late-1990s Interactive Music Videos
  • Streaming Vector Graphics

More comparisons

JPEG-XS-(HEIF) vs ACES → RealFlash vs ACES → JPEG-XS-(HEIF) vs APNG → RealFlash vs APNG → JPEG-XS-(HEIF) vs AVCI → RealFlash vs AVCI → JPEG-XS-(HEIF) vs AVCS → RealFlash vs AVCS → JPEG-XS-(HEIF) vs AVIF → RealFlash vs AVIF → All comparisons →
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