Free webp to jpg
EN
Image MIME Reference
HEIF-Sequence

High Efficiency Image File Format Sequence

image/heif-sequence
VS

RealNetworks RealFlash

image/vnd.rn-realflash
RealFlash

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

Equal browser support

Feature Support

Feature HEIF-Sequence RealFlash
Transparency (Alpha) Yes Yes
Animation Support Yes Yes
Progressive Loading ✕ No Yes
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 →
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 HEIF-Sequence RealFlash
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
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

HEIF-Sequence
Use HEIF-Sequence when…
  • Burst Photography
  • Focal Stacking
  • Exposure Bracketing
  • Time-Lapse Data
RealFlash
Use RealFlash when…
  • Historical Dial-up Web Animation
  • Late-1990s Interactive Music Videos
  • Streaming Vector Graphics

More comparisons

HEIF-Sequence vs ACES → RealFlash vs ACES → HEIF-Sequence vs APNG → RealFlash vs APNG → HEIF-Sequence vs AVCI → RealFlash vs AVCI → HEIF-Sequence vs AVCS → RealFlash vs AVCS → HEIF-Sequence vs AVIF → RealFlash vs AVIF → All comparisons →
Share this comparison