Image MIME Reference
JPEG-LS
JPEG-LS
image/jls
VS
RealNetworks RealFlash
image/vnd.rn-realflash
RealFlash
A complete technical comparison of JPEG-LS and RealNetworks RealFlash — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JPEG-LS | RealFlash |
|---|---|---|
| Transparency (Alpha) | ✕ No | Yes |
| Animation Support | ✕ No | Yes |
| Progressive Loading | ✕ No | Yes |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | ✕ No | ✕ No |
JPEG-LS
image/jls
Extension
.jls.jl
Container
JPEG Bitstream
Compression
Lossless / Near-Lossless (Predictive Coding)
Algorithm
LOCO-I (Low Complexity Lossless Compression for Images)Golomb-Rice Coding
Color Depth
8-bit, 12-bit, 16-bit (Per Channel)
Developed by
Joint Photographic Experts Group (ISO/ITU-T) & HP Labs
Released
1999
Magic Bytes
FF D8 FF F7
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)
Browser Support Comparison
| Browser | JPEG-LS | RealFlash |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
JPEG-LS
JPEG-LS Strengths
- Provides state-of-the-art lossless compression ratios for continuous-tone images, often outperforming Lossless JPEG and JPEG 2000
- Extremely fast and computationally inexpensive to encode/decode, requiring no complex floating-point math or DCTs
- Highly resilient in constrained hardware environments, making it ideal for medical equipment and deep-space probes (e.g., Mars rovers)
Limitations
- Zero native support in web browsers or standard consumer operating systems
- Lacks the advanced resolution scalability and progressive decoding features found in JPEG 2000
- Primarily relegated to niche enterprise sectors (healthcare/DICOM and aerospace) rather than consumer adoption
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-LS
Use JPEG-LS when…
- Medical Imaging (DICOM Encapsulation)
- Space and Planetary Imaging (NASA/ESA)
- Industrial Machine Vision
- Scientific Archival Storage
RealFlash
Use RealFlash when…
- Historical Dial-up Web Animation
- Late-1990s Interactive Music Videos
- Streaming Vector Graphics