Move dead submodules in-tree

Signed-off-by: swurl <swurl@swurl.xyz>

externals/oboe/samples/SoundBoard/README.md

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+Soundboard
+==========
+Do you want to just jam with some digital tunes? Now you can!
+
+This sample demonstrates how to obtain the lowest latency and optimal computational throughput by:
+
+1) Leaving Oboe to choose the best default stream properties for the current device
+2) Setting performance mode to LowLatency
+3) Setting sharing mode to Exclusive
+4) Setting the buffer size to 2 bursts
+5) Using the `-Ofast` compiler optimization flag, even when building the `Debug` variant
+
+The [following article explaining how to debug CPU performance problems](https://medium.com/@donturner/debugging-audio-glitches-on-android-ed10782f9c64) may also be useful when looking at this code.
+
+Implementation details
+---
+The stream properties are left to Oboe as such the app must output audio data in a format which matches that of the stream. 
+
+Four different formats are supported: 
+
+|Channel count|Format|
+|-------------|------|
+|1 - Mono|16-bit int|
+|2 - Stereo|16-bit int|
+|1 - Mono|Float|
+|2 - Stereo|Float|
+
+The signal chain for mono streams is: 
+
+    SynthSound->Mixer
+
+For stereo chains a mono to stereo converter is added to the end of the chain: 
+
+    SynthSound->Mixer->MonoToStereo
+ 
+The compiler optimization flag `-Ofast` can be found in [CMakeLists.txt](CMakeLists.txt). 
+
+Each SynthSound is a series of 5 Oscillators, creating a pleasant sounding note when combined.
+
+The number of notes depends on the shape of the screen, with G3 being the first note.
+
+In order to determine whether a note should be played, MusicTileView demonstrates how to keep track of where each finger is.
+
+Images
+-----------
+![soundboard_image](soundboard_image.png)