Base class for video encoding. This uses createInputSurface to create an input Surface into which we can write and that MediaCodec itself can read. This makes everything easier with respect to the process explained in MediaEncoder docs. We can skip the whole input part of acquiring an InputBuffer, filling it with data and returning it to the encoder with encodeInputBuffer. All of this is automatically done by MediaCodec as long as we keep writing data into the given Surface. This class alone does not do this - subclasses are required to do so.