When using SharpAvi, frames occassionally get dropped and the Texture2DFrame.CopyTo method produces a transparent frame. This has been observed to happen when recording the Windows desktop applications such as File Explorer. This causes the recording to flicker and have flashes of empty frames.

The fix checks for transparency by comparing the current frame to all zeros, and uses the previously saved frame if necessary. For performance, it uses memcmp to compare to a byte array prefilled with zeros.

Use a token, such as a GUID, which can be used to stop a recording.

Can be used with or without length:
- If no length is provided, recording will continue indefinitely
  until a token signal is sent.
- If a length is provided, recording will continue until the time
  has expired or a token signal is sent, whichever arrives first.

Example code to stop a recording that was started using --stop ABCDE:

var doneWithInit = new EventWaitHandle(
    false, EventResetMode.ManualReset, "ABCDE");
doneWithInit.Set();