Is there any way that DASH M4A files can be supported? (the ones from YouTube etc.) VLC can play them fine as well as chrome natively.
The only real solution is to use ffmpeg:
ffmpeg -i "dashfile.m4a" -codec copy "out.m4a"
The file does not change too substantially, it still uses normal AAC encoding, but different headers, and uses Movie Fragment (moof) to spit the data into chunks.

This is a binary diff of a 3MB DASH file vs. a 3MB working converted file - not much change (beside top and bottom, the even lines are 1824-byte moof chunks)