2.0 -- version 2.0 of the core HIDL API. Note that .hal files can not be moved into the core directory because that would change its namespace and include path.
- config -- the XSD schema for the Audio Policy Manager configuration file.
4.0 -- version 4.0 of the core HIDL API.
...
common -- common types for audio core and effect HIDL API.
- 2.0 -- version 2.0 of the common types HIDL API.
- 4.0 -- version 4.0.
- ...
- 7.0 -- version 7.0.
  - example -- example implementation of the core and effect V7.0 API. It represents a "fake" audio HAL that doesn't actually communicate with hardware.
- all-versions -- code common to all version of both core and effect API.
  - default -- shared code of the default implementation.
    - service -- vendor HAL service for hosting the default implementation.
  - test -- utilities used by tests.
  - util -- utilities used by both implementation and tests.
core -- VTS tests and the default implementation of the core API (not HIDL API, it's in audio/N.M).
- 7.0 -- code specific to version V7.0 of the core HIDL API
- all-versions -- the code is common between all versions, version-specific parts are enclosed into conditional directives of preprocessor or reside in dedicated files.
  - default -- code that wraps the legacy API (from hardware/libhardware).
  - vts VTS tests for the core HIDL API.
effect -- same for the effect HIDL API.
- 2.0
  - config -- the XSD schema for the Audio Effects configuration file.
- 4.0
- ...
- all-versions
  - default
  - vts
policy -- Configurable Audio Policy schemes.
- 1.0 -- note that versions of CAP are not linked to the versions of audio HAL.
  - vts -- VTS tests for validating actual configuration files.
  - xml -- XSD schemas for CAP configuration files.