  Physical parameters of AGN jets observed with Very Long Baseline
Interferometry (VLBI) are usually inferred from the core shift measurements or
flux and size measured at a peak frequency of the synchrotron spectrum. Both
are preceded by modelling of the observed VLBI jet structure with a simple
Gaussian templates. We propose to infer the jets parameters using the
inhomogeneous jet model directly - bypassing the modelling of the source
structure with a Gaussian templates or image deconvolution. We applied Bayesian
analysis to multi-frequency VLBA observations of radio galaxy NGC 315 and found
that its parsec-scale jet is well described by the inhomogeneous conical model.
Our results favour electron-positron jet. We also detected a component in a
counter jet. Its position implies the presence of an external absorber with a
steep density gradient at close ($r=0.1$ pc) distance from the central engine.
