Return current volume setting, the actual value due to RVA, and the RVA
adjustment itself. It's all as double float value to abstract the sample
format. The volume values are linear factors / amplitudes (not percent)
and the RVA value is in decibels.
\param mh handle
\param base return address for base volume (linear factor)
\param really return address for actual volume (linear factor)
\param rva_db return address for RVA value (decibels)
\return MPG123_OK on success
Return current volume setting, the actual value due to RVA, and the RVA adjustment itself. It's all as double float value to abstract the sample format. The volume values are linear factors / amplitudes (not percent) and the RVA value is in decibels. \param mh handle \param base return address for base volume (linear factor) \param really return address for actual volume (linear factor) \param rva_db return address for RVA value (decibels) \return MPG123_OK on success