Faster way to get raw texture data than Texture2D.ReadPixels?

I want to capture the screen the user is seen and send that data as a byte array to a remote machine, running another Unity3D application.

I am using Texture2D.GetRawTextureData() at present, but after timing it, I see that it takes up to 12 milliseconds:

 private byte[] FrameData;
 public IEnumerator SetFrame()
 {
     // Can take up to 12 ms!
     yield return new WaitForEndOfFrame();
 
     int width = Screen.width;
     int height = Screen.height;
 
     Texture2D tex = new Texture2D(width, height, TextureFormat.RGB24, false);

     var sw = new System.Diagnostics.Stopwatch();
     sw.Start();
     tex.ReadPixels(new Rect(0, 0, width, height), 0, 0);
     Debug.Log(sw.ElapsedMilliseconds.ToString());

     FrameData = tex.GetRawTextureData();
     Destroy(tex);
 }

On this other machine, I do the following to display the image to the user:

 void DisplayFrame(byte[] frame)
 {
     //3ms at most
     Texture2D texture = new Texture2D(Screen.width, Screen.height, TextureFormat.RGB24, false);
     texture.LoadRawTextureData(frame);
     texture.Apply();
     GetComponent<Renderer>().material.mainTexture = texture;
 }

Is there something faster than ReadPixels?

(PS how the hell do I insert a new line between sentences? This editor just ignores them!)