Can Dialnorm metadata be present in a stereo mix? I have a stereo mix film that when processed through OP59 loudness algorithms somehow produces a ramp in overall levels during voice only scenes with no or very little background sound. (i.e. two people talking at normal levels in a quiet room)
Dialnorm metadata are part of ac3 (Dolby Digital) standard. When encoding a stereo soundtrack in ac3, you must set the dialnorm metadata. OP59 indicates that the dialnorm should be set at the loudness level of the full program measured with a BS1770 compliant meter.
If by 'OP59 loudness algorithms' you mean a dynamic processor that processes your mix, setting the appropriate dialnorm will probably have no effect, as dialnorm is mostly used by customers receivers. If you give some details, we might be able to give a more comprehensive answer.