How Android Integrates libavif for Native AVIF

This article provides an overview of how the Android Open Source Project (AOSP) incorporates the libavif library to enable native AV1 Image File Format (AVIF) support. It details the architectural integration within the Android media framework, the relationship between libavif and AV1 decoders, and how developers benefit from this implementation starting from Android 12.

The Role of libavif in AOSP

Beginning with Android 12 (API level 31), Google introduced system-wide, native support for the AVIF image format. To decode and encode these highly compressed images, AOSP integrates libavif—an open-source C library developed by the Alliance for Open Media (AOM). Located within the AOSP source tree under the external/libavif directory, this library serves as the core engine for parsing the container structure of AVIF files, which are based on the ISO Base Media File Format (ISOBMFF).

Architecture and Decoding Pipeline

While libavif is responsible for parsing the container metadata, color profiles, and grid layouts of an AVIF image, it does not decode the raw AV1 video bitstream itself. Instead, the integration relies on a modular pipeline within Android’s media framework:

1. API Layer: When an application requests an image via standard APIs like BitmapFactory or ImageDecoder, the request is routed to Android’s native graphics pipeline (libhwui).
2. Container Parsing: The framework invokes libavif to parse the AVIF file container, extracting essential metadata such as image dimensions, rotation, alpha channels, and depth maps.
3. AV1 Bitstream Decoding: To decode the actual compressed image data, libavif interfaces with Android’s system-level AV1 decoders. In AOSP, this is typically handled by libgav1 (a software AV1 decoder) or a hardware-accelerated AV1 decoder provided by the device’s chipset manufacturer via the MediaCodec framework.
4. Rendering: Once decoded, the raw pixel data is handed back to the Android graphics system to be rendered as a standard Bitmap.

Support for Advanced Imaging Features

By integrating libavif directly into the operating system platform, Android natively supports advanced features of the AVIF format without requiring third-party libraries at the application level. This includes:

• High Dynamic Range (HDR): Support for 10-bit and 12-bit color depth, as well as Wide Color Gamut (WCG) color spaces.
• Alpha Channels: Seamless handling of transparent overlays and lossless auxiliary images.
• Monochrome and Multi-channel Images: Efficient storage of grayscale and specialized image types.

Benefits of System-Level Integration

Integrating libavif directly into AOSP ensures that all Android applications can automatically read and write AVIF files without increasing their APK size. This system-level support enables apps to utilize AVIF’s superior compression efficiency—which significantly outperforms JPEG and WebP in quality-to-file-size ratio—while maintaining fast, standardized, and secure decoding across a wide variety of Android devices.