The present invention provides a process for decreasing the content of 1-propyl)-1–1,3-dihydro-5-halo-isobenzofuran, a compound of formula 1, wherein X is halogen, by converting to a compound of formula 3, comprising subjecting 1-propyl)-1–1,3-dihydro-5-halo-isobenzofuran present as impurity in crude 1-3-propyl-1–1,3-dihydro-5-isobenzofuran carbonitrile to hydrogenolysis. The embedded watermark has data characteristic of stream quality. The control circuit is configured to periodically enable the delay locked loop in standby mode at an update interval and for an enable period.