For dolby media codecs to work add this line in your media codecs config (should be in vendor partition) and make sure your device supports c2 codecs. :-

<Include href="media_codecs_dolby_audio.xml" />

To build, add the dolby effects in your device's audio effects config then inherit the dolby config by adding this in your device's makefile :-

$(call inherit-product, hardware/dolby/dolby.mk)

Now, moving hidl definitions in manifest to device trees is completely absurd so stop overriding manifest in your device trees an example for such would be :-

Changing these in BoardConfig makefile of your device tree:-

DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE :=

And

DEVICE_MANIFEST_FILE :=

To:-

DEVICE_FRAMEWORK_COMPATIBILITY_MATRIX_FILE +=

And

DEVICE_MANIFEST_FILE +=

The only change done above is changing := symbol to += so that manifest can't be overriden from device tree in BoardConfig makefile.

At the end an example commit to properly implement it in your device tree could be :- https://github.com/Neoteric-OS/device_nothing_Pong/commit/cefa46567c04770e492351e51dd96cfae80e34fb