HEIF vs AVIF: Structural Relationship Explained

AVIF and HEIF share a direct parent-child architectural relationship rather than being completely distinct formats. HEIF (High Efficiency Image File Format) serves as a standardized media container framework, while AVIF (AV1 Image File Format) is a specific profile within the HEIF family. Understanding their connection requires looking at how their container architecture, codec payloads, and metadata systems interact.

The Shared ISOBMFF Foundation

At their structural core, both HEIF and AVIF are built upon the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12). ISOBMFF organizes data into modular, nested blocks called "boxes" (or atoms).

Because both formats inherit this specification, they organize media payloads using identical structural mechanisms:

• The ftyp (File Type) Box: Appears at the very beginning of the file to declare the brand, minor version, and compatible profiles. A HEIF file commonly identifies as mif1 or heic, whereas an AVIF file identifies using the avif or avis (for sequences) brand.
• The meta (Metadata) Box: Stores resource structures, identifying where the primary image, thumbnails, and auxiliary data reside.
• The mdat (Media Data) Box: Contains the actual raw encoded byte stream of the image or sequence.

Container vs. Codec

The distinction between HEIF and AVIF lies in the compression codec packaged inside the container:

• HEIF (ISO/IEC 23008-12): Standardized by the Moving Picture Experts Group (MPEG), HEIF defines general rules for packaging static images, image sequences, and auxiliary items. While HEIF can theoretically hold various formats, its primary and original deployment wraps HEVC (H.265) compressed bitstreams, usually denoted with the .heic extension.
• AVIF: Standardized by the Alliance for Open Media (AOMedia), AVIF explicitly defines how to encapsulate AV1-compressed bitstreams inside the HEIF container format. Structurally, AVIF does not reinvent the file format; it merely replaces HEVC payload boxes with AV1 configuration and sample data.

Structural Inheritance

Because AVIF uses HEIF as its structural template, it directly inherits HEIF's advanced architectural capabilities:

• Alpha Channels: AVIF achieves transparency by using HEIF’s auxiliary image references, linking a secondary monochrome image item as an alpha plane for the primary image item.
• Image Sequences and Animations: AVIF uses HEIF’s sequence track definitions to store multi-frame animations or burst shots without adopting a container like GIF or APNG.
• Derived Items and Non-Destructive Edits: AVIF leverages HEIF's derived image items, allowing instructions like rotation, mirroring, or overlay cropping to be applied structurally via metadata without re-encoding the compressed pixels.
• Color and Dynamic Range: AVIF supports High Dynamic Range (HDR) and Wide Color Gamut (WCG) by storing standardized ICC profiles and NCLX boxes defined in the HEIF specification.

AVIF is structurally an instance of a HEIF file tailored to hold AV1 video compression data, maintaining identical file hierarchies while swapping the underlying compression format.