diff --git a/README.md b/README.md
index eac7e37..b7f2d95 100644
--- a/README.md
+++ b/README.md
@@ -1606,8 +1606,15 @@ installed.
 - __ascii__ - add various "density" ASCII characters over the rendering to give
   the image more detail, similar to libcaca/libcucul (the library mplayer uses
   to display videos in the terminal).
-- __animate__ - whether to animate if the image is an APNG. if false, only
-  display the first frame or IDAT (default: `true`).
+- __animate__ - whether to animate if the image is an APNG/animating GIF. if
+  false, only display the first frame or IDAT (default: `true`).
+- __speed__ - set the speed of animation. slower: `0.0-1.0`. faster: `1-1000`.
+  it cannot go faster than 1 frame per millisecond, so 1000 is the fastest.
+  (default: 1.0)
+- __optimization__ - `mem` or `cpu`. if optimizing for memory, animation frames
+  will be rendered to bitmaps _as the animation plays_, using less cpu.
+  optimizing for cpu will precompile all bitmaps beforehand, which may be
+  faster, but might also OOM the process on large images. (default: `mem`).
 
 ##### Properties:
 
diff --git a/vendor/tng.js b/vendor/tng.js
index 713047c..d14ed44 100644
--- a/vendor/tng.js
+++ b/vendor/tng.js
@@ -51,7 +51,6 @@ function PNG(file, options) {
     try {
       return this.toPNG(buf);
     } catch (e) {
-      console.error('could not convert ' + this.format + ' to png');
       throw e;
     }
   }