Add conversion from float to fixed-point i16

To encode float values between -1 and 1.

PR #3369 <https://github.com/Genymobile/scrcpy/pull/3369>

server/src/main/java/com/genymobile/scrcpy/Binary.java

@@ -24,4 +24,15 @@ public final class Binary {
         // 0x1p16f is 2^16 as float
         return unsignedShort == 0xffff ? 1f : (unsignedShort / 0x1p16f);
     }
+
+    /**
+     * Convert signed 16-bit fixed-point to a float between -1 and 1
+     *
+     * @param value encoded value
+     * @return Float value between -1 and 1
+     */
+    public static float i16FixedPointToFloat(short value) {
+        // 0x1p15f is 2^15 as float
+        return value == 0x7fff ? 1f : (value / 0x1p15f);
+    }
 }