Derrick: "If you don't agree that visual experience is the output of the visual process, then we'll have to agree to disagree"

I personally believe that visual experience is indeed the output of the visual process but I am pointing out that Direct Realists believe that it isn't. Given that your argument is an argument against Direct Realism you cannot agree to disagree with their central thesis. Direct realism is defined as the proposal that visual experience is not the output of the visual process. In the Standord Encyclopedia of Philosophy BonJour(2007) says:

"Viewed as an alternative to representative realism in particular, direct realism involves two main theses. The first is a denial of the view referred to here as perceptual subjectivism: according to direct realism, in veridical cases we directly experience external material objects, without the mediation of either sense-data or adverbial contents.  ..."

I know this is absurd but Direct Realism really does posit experience without mediation. As Thomas Reid might have put it, the soul is believed to be directly connected with the world beyond the body.

I believe that the best arguments against Direct Realism are those that examine phenomena such as perceptual filling in and perceptual masking. In the first case we experience phenomena that definitely do not exist in the external material world but which are indistinguishable from it and in the case of the phi illusion 0.5 seconds delayed. In the second case we can blank out data after it has entered the brain provided the second, blanking stimulus occurs within about 0.5 secs.  The reason these physiological arguments are little used in philosophy is that they have the implication that all experience is 0.5 seconds delayed....which is true but awkward.  Your time gap argument could be modified into a "buffering within the brain for 0.5 secs" argument then it might indeed dispatch Direct Realism.

BonJour, Laurence, "Epistemological Problems of Perception", The Stanford Encyclopedia of Philosophy (Summer 2011 Edition), Edward N. Zalta (ed.), <http://plato.stanford.edu/archives/sum2011/entries/perception-episprob/>.