Use legacy SVC encoding specification for React-Native (#1093)

* test rn

* fix

* changeset

Author: davidzhao

.changeset/chilly-grapes-report.md

@@ -0,0 +1,5 @@
+---
+"livekit-client": patch
+---
+
+Use legacy SVC encoding specification for React-Native

example/sample.ts

@@ -99,6 +99,7 @@ const appActions = {
         red: true,
         forceStereo: false,
         screenShareEncoding: ScreenSharePresets.h1080fps30.encoding,
+        scalabilityMode: 'L3T3',
       },
       videoCaptureDefaults: {
         resolution: VideoPresets.h720.resolution,

src/room/participant/publishUtils.ts

@@ -149,6 +149,10 @@ export function computeVideoEncodings(
     const browser = getBrowser();
     if (
       isSafari() ||
+      // Even tho RN runs M114, it does not produce SVC layers when a single encoding
+      // is provided. So we'll use the legacy SVC specification for now.
+      // TODO: when we upstream libwebrtc, this will need additional verification
+      isReactNative() ||
       (browser?.name === 'Chrome' && compareVersions(browser?.version, '113') < 0)
     ) {
       const bitratesRatio = sm.suffix == 'h' ? 2 : 3;