MMAL

MMAL stands for Multimedia Abstraction Layer. It is a software framework used on Raspberry Pi devices that provides a high-level API to access hardware-accelerated media processing on the VideoCore GPU. MMAL serves as a bridge between applications and the hardware components such as cameras, encoders, decoders, and image processors, enabling the creation of media pipelines with relatively little device-specific code.

The API exposes components with multiple ports and uses buffers to transfer data. A typical pipeline consists of creating components (for example a camera or an encoder), connecting output ports to input ports, allocating buffers, and starting streaming. Through these ports, data flows from source to sink, with parameters adjustable via control interfaces.

MMAL is part of the Raspberry Pi multimedia stack and is implemented in C as libmmal and related libraries. It is designed to be lighterweight than OpenMAX IL and is tailored to the Pi's VideoCore hardware, emphasizing efficiency and direct GPU-assisted processing. The API has also spawned language bindings and third-party wrappers, including Python interfaces used by the picamera project.

Usage and ecosystem: Applications such as raspivid and raspistill use MMAL to capture video and still images; Python libraries provide higher-level access to the camera through MMAL.

Relation to libcamera: In recent years, libcamera has emerged as the preferred framework for Raspberry Pi camera support, and official guidance points to libcamera as the modern stack. MMAL remains available in older firmware and applications, but may have limited support going forward.