Windows Media Audio (WMA) / ASF Data Structure

I'm reading a wma file as a 1D array of bytes. I want to know which item in the array is the start of the music data.

I understand that this can be calculated using the header data but I can't work it out. I've tried reading up on the WMA file structure (e.g. the first 128 bits being the Object ID, the next 64 bits being the Object Size and so on) but despite a lot of time spent on this, I'm still lost.

Can anyone please end this headache?!