Smooth streaming - How does silverlight choose default language track in multi audio manifest

Question

I have a smooth stream source with English and Spanish audio tracks. When player starts playing - English is the default language. How does it get set which is the default audio language track?

A few related details:

• In the manifest the Spanish audio track appears before the English one.
• The English audio track has index=0 attribute and Spanish has index=1.

A few test results:

1. If I edit the XML manually and change the indexes so Spanish index=0 and English index=1 nothing changes, English is still default.
2. If I edit the XML manually and change the order of the tracks in the XML, e.g. English appears before Spanish then Spanish is the default language.

The conclusion from above is that last Audio segment in manifest is the default one. I can't find any documentation supporting this assumption. Would appreciate any supporting comment or documentation for this.

Thanks.