Image MIME Reference
JPEG-XS-Sequence
JPEG XS Image Sequence (HEIF Container)
image/jxss
VS
PiCture eXchange
image/x-pcx
PCX
A complete technical comparison of JPEG XS Image Sequence (HEIF Container) and PiCture eXchange — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | JPEG-XS-Sequence | PCX |
|---|---|---|
| Transparency (Alpha) | Yes | ✕ No |
| Animation Support | Yes | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | Yes | ✕ No |
| ICC Color Profile | Yes | ✕ No |
JPEG XS Image Sequence (HEIF Container)
image/jxss
Extension
.jxss.jxs
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 73
PiCture eXchange
image/x-pcx
Extension
.pcx
Container
ZSoft Proprietary Header (128 bytes)
Compression
Run-Length Encoding (RLE)
Algorithm
ZSoft RLE
Color Depth
1-bit (Monochrome), 4-bit (16 colors), 8-bit (256 colors), 24-bit (True Color)
Developed by
ZSoft Corporation
Released
1985
Magic Bytes
0A (followed by version, e.g., 0A 05 01 08)
Browser Support Comparison
| Browser | JPEG-XS-Sequence | PCX |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
JPEG-XS-Sequence
JPEG-XS-Sequence Strengths
- Provides sub-millisecond encoding and decoding latency across a video sequence while retaining visually lossless quality
- Leverages the robust ISOBMFF track structures for accurate frame timing, audio synchronization, and metadata handling
- Optimized for professional video production and IP broadcasting workflows
Limitations
- Zero web browser compatibility, limiting its use entirely to professional and industrial hardware workflows
- Compression ratios are significantly lower than consumer video codecs like HEVC or AV1
- Extremely niche format that requires highly specialized broadcast hardware or custom software libraries to process
PCX
PCX Strengths
- Incredibly simple RLE algorithm makes it very fast to decode, which was historically vital for early 3D video game engines
- Retains crisp, lossless pixel data suitable for pixel art and interface assets
- Well-documented and highly supported by older desktop publishing and image editing software
Limitations
- Extremely inefficient compression by modern standards, producing large file sizes compared to PNG
- Lacks modern imaging features such as alpha channel transparency, EXIF metadata, and color profiles
- Zero support in web browsers; must be converted to PNG for web use
When to choose which format
JPEG-XS-Sequence
Use JPEG-XS-Sequence when…
- Live Broadcast Video Snippets
- Medical Imaging Sequences
- HDR Burst Photography Archiving
- Automotive & Drone Video Storage
PCX
Use PCX when…
- MS-DOS and Early Windows Graphics
- 1990s Video Game Assets (Textures, UI)
- Retro Computing Archival