  We have updated our extraction of the transversity parton distribution based
on the analysis of pion-pair production in deep-inelastic scattering off
transversely polarized targets in collinear factorization. The most recent
COMPASS data for proton and deuteron targets, complemented by previous HERMES
data on the proton, make it possible to perform a flavor separation of the
valence components of the transversity distribution, using di-hadron
fragmentation functions taken from the semi-inclusive production of two pion
pairs in back-to-back jets in $e^+ e^-$ annihilation. The $e^+ e^-$ data from
BELLE have been reanalyzed to reach a more realistic estimate of the
uncertainties on the chiral-odd interference fragmentation function. Our
results represent the most accurate estimate of the uncertainties on the
valence components of the transversity distribution currently available.
