Add webrtc docs (#13)

docs/webrtc_guide.md

@@ -0,0 +1,49 @@
+# WebRTC Android guide
+
+Currecntly we're using the fork of Chromium's WebRTC library from here: 
+
+## Initial setup
+
+Compiling webrtc for Android works only on Linux, so if you're using Mac, use for example Docker. I've used circleci's `cimg/android` image. Run the following commands:
+```
+git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
+export PATH=/home/circleci/project/depot_tools:$PATH # or whatever path you have depot_tools in 
+```
+to install Chromium depot tools.
+
+If you want to compile the fork, change the address of the repo in `depot_tools/fetch_configs/webrtc.py` from `'https://webrtc.googlesource.com/src.git'` to `'https://github.com/webrtc-sdk/webrtc.git'`. Depot tools will now automatically handle cloning the fork and dependencies.
+
+Pro tip if you're using docker: you can attach VSCode to docker container and edit files there as if they were on your local machine using Docker extension.
+
+Then create the new directory and fetch the repo there:
+```
+mkdir webrtc-checkout
+cd webrtc-checkout/
+fetch --nohooks webrtc_android
+gclient sync
+```
+
+## Compiling
+Then you can build the aar for Android with this command:
+```
+cd src
+./tools_webrtc/android/build_aar.py --build-dir webrtc_android --output ./webrtc_android/libwebrtc.aar --arch arm64-v8a --extra-gn-args 'is_java_debug=true rtc_include_tests=false rtc_use_h264=false is_component_build=false use_rtti=true rtc_build_examples=false treat_warnings_as_errors=false'
+```
+
+Note that there is only one architecture for quicker compilation, specify more if needed.
+
+Also I have a problem that sometimes compilation freezes (maybe it's specific for my configuration). Just kill it and try again - you won't lose progress. If you keep webrtc_android folder, the next compilations will be quicker.
+
+## Adding compiled library to the project
+
+After compiling add it to Android project. In `build.gradle` in MembraneRTC module replace `api 'com.github.webrtc-sdk:android:104.5112.01'` with `api files('./libs/libwebrtc.aar')`. Then copy aar from docker to the project like this:
+`docker cp container_name:/home/circleci/project/src/webrtc_android/libwebrtc.aar path/to/project/membrane-webrtc-android/MembraneRTC/libs/libwebrtc.aar`
+
+To enable logs from cpp into logcat add `Logging.enableLogToDebugOutput(Logging.Severity.LS_INFO)` after initializing `PeerConnectionFactory`.
+
+## A handy script for compiling & copying
+```
+#!/bin/bash
+docker exec -t webrtc_fork sh -c "export PATH=/home/circleci/project/depot_tools:$PATH && cd /home/circleci/project/webrtc-checkout/src && ./tools_webrtc/android/build_aar.py --build-dir webrtc_android --output ./webrtc_android/libwebrtc.aar --arch arm64-v8a --extra-gn-args 'is_java_debug=true rtc_include_tests=false rtc_use_h264=false is_component_build=false use_rtti=true rtc_build_examples=false treat_warnings_as_errors=false'"
+docker cp webrtc_fork:/home/circleci/project/webrtc-checkout/src/webrtc_android/libwebrtc.aar /Users/angelikaserwa/Projects/membrane-webrtc-android/MembraneRTC/libs/libwebrtc.aar
+```