Unable to schedule a timer Error in Waveform Example

Firstly, I saw the PWM does not work. Code exists but doesn't work. in the ESP8266 reference.
But when I tried the simple example ( analogWrite(D12, 0.5)) , I measured the voltage half of 3.3V at the D12 pin. So I thought that PWM is running. And then,

I tried Waveform example but I can not run this example on ESP8266.

var s = atob("f4GBgoODh5GtnmgkE1m435g/MobgzYJbd4­1YHkHD/7UoEZPysyscl/K5PSqLy5tLToqdfHGdrX­I1V7vUeiVIqceEUG2kmWVfj6qIWFuKpZFpXXiXkn­NthZB9cH6LgG5vgJKSdWF7oZVoXHuRioJ8c3iJjH­tweomLf3JygpCHdHOCiYJ8fYCBg4ODgn53d4CGiI­Z8cHGAjo1+dn6Jh3pzeoWHfXd8hYd8d3+Gg3t1e4­F9d36KiHp0fYZ+cneLlol3cnyEgXt8g4WBeXV8ho­qDdnOCjoNxc4aRhnd3f4J6cXmNlIJxd4mKeXJ5iI­2Denh9fX1/f4B/g4N2bnuSlYJzdoOIgXp7g4V+dn­mDhoF9gIF+eHqDioJyb3+Oi3xzeIOHgXp7gIB+fH­+DgHt8hIh/cnOEjoVzb32Mi3pxeYeLf3N2hIqBdX­aBhoB7fYSGfXZ7hYeAeXl9goJ9e36BgYGCgoF8e4­GDgHp6f4ODgHo=");
var w = new Waveform(s.length);
w.buffer.set(s);
BUZZER = D12
analogWrite(BUZZER, 0.5, {freq:20000}); 
w.startOutput(BUZZER,4000);

I got WARNING:Unable to schedule a timer. error.

How can I fix it ? or Is the PWM does not run yet on ESP8266?