Fixes #327
Instead of hardcoding mp3 as the format to use for cache-ahead audio, the priority order is defined for all the possible formats (with mp3 as the highest priority). The actual audio format to use is the first audio format (according to that priority list) that is actually available. This allows files that are being requested at the native sample rate to be cached where the native sample rate is not supported by mp3.
Fixes #327 Instead of hardcoding mp3 as the format to use for cache-ahead audio, the priority order is defined for all the possible formats (with mp3 as the highest priority). The actual audio format to use is the first audio format (according to that priority list) that is actually available. This allows files that are being requested at the native sample rate to be cached where the native sample rate is not supported by mp3.