Help with reconstructing GMSK IQ from ogg files

Hello everyone,

I need help understanding the .ogg audio files from observations. To be more specific, I am interested in GMSK. If I understand correctly, the data inside .ogg files is already demodulated using quadrature demodulation. How can I get raw IQ from the .ogg file? Can I just cumulatively sum the values and apply the sine() and cosine() functions to get the I and Q values? Do I need to somehow scale the values first? How can I know the sample rate?

Thanks in advance,