International audienceWe generalize Koopman-von Neumann classical mechanics to relativistic field theory. The manifestly covariant Koopman-von Neumann mechanics formulated over polysympletic fields leads to De Donder-Weyl mechanics. Comparing this polysymplectic formulation with Dirac's quantization leads to a new Hamiltonian density that is canonical and covariant with symplectic structure. We provide the commutation relations for these classical and quantum fields with a new type of canonical momentum that has the covariant structure of the De Donder-Weyl poly-momentum, yet has the symplectic geometry of Dirac's conjugate momentum. For the first time, we clarify how 1st and 2nd quantization relates to an algebraic deformation of commutati...