Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 356c1df1 authored by Jeremy Wu's avatar Jeremy Wu Committed by Automerger Merge Worker
Browse files

Merge "Floss: add mmc README.md" into main am: cec17cf2 am: 36e785f8 

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2748694



Change-Id: I8218cd0f26996d7abd31d12af68e8df895c04ca8
Signed-off-by: default avatarAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
parents 21dcb493 36e785f8

system/stack/mmc/README.md

0 → 100644
+45 −0
Original line number Diff line number Diff line 
# Minijailed Media Codec (MMC)



MMC is a service running in minijail that isolates codec implementations from

the Bluetooth process and system resources. It is an independent daemon that

spawns codec servers on demand to communicate with their corresponding codec

clients living in Floss.



## Steps to Apply MMC to a New Codec



### 1. Implement codec server



  * Wraps third party library codes.

  * Codec server should inherit [MMC Interface](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/stack/mmc/mmc_interface/mmc_interface.h).

    * public methods: `init`, `cleanup`, `transcode`.

    * `init`: set up transcoder and return frame size accepted by the transcoder.

    * `cleanup`: clear the transcoder context.

    * `transcode`: transcode input data, store result in the given output buffer,

                   and return the transcoded data length.



### 2. Add codec proto message in [mmc_config.proto](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/stack/mmc/proto/mmc_config.proto)



  * Define a proto message for the new codec, generally, it may include:

    * Init configuration.

    * Transcode arguments or params.

    * Library-specific enum mappings.

  * Append an entry to [`ConfigParam`](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/stack/mmc/proto/mmc_config.proto;drc=1e6b2d44402d18cce637f4b02d4da25133924662;l=99).



### 3. Add codec support in MMC daemon



  * Match the new `ConfigParam` to create its corresponding server in [`CodecInit`](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/stack/mmc/daemon/service.cc;drc=e9fcc3a7897c6af3df4163534688290778e2333b;l=186).



### 4. Access the interface via [`CodecClient`](https://cs.android.com/android/platform/superproject/main/+/main:packages/modules/Bluetooth/system/stack/mmc/codec_client/codec_client.h) from within the BT process



  * BT process accesses codec implementations via `CodecClient`.

    * `init`: set up `ConfigParam` and pass it to `CodecClient`.

    * `transcode`: pass input and output buffer, and specify the input data size

                   and the output buffer capacity. `transcode` returns transcoded

                   data length on success, and negative error number otherwise.

    * `cleanup`: when a session ends, `cleanup` should be called.



## Related links



* Design doc: go/floss-mmc

* Slides: go/floss-mmc-presentation

* Performance evaluation: go/floss-mmc-experiment