I'm endeavoring to build an audio player using the Tessel 2 and I was running into an issue. Most of my audio files are m4a/aac encoded and madplay (which tessel-av uses) can't play them. So, I needed to find an AAC decoder that was fast enough to transcode them. I tried ffmpeg but it was far too slow and I kept getting buffer underruns. Then, I tried SOX but not only was it a pain to install but it didn't work properly either. Finally, I found FAAD2 which IS, in fact, fast enough to decode the file and pipe the data to aplay without it skipping.
Now that I've got something I'm working on the front-end code. I'll post a link to the github repo when I've got something worth showing. Just wanted to post this here in case someone else was trying to decode AAC files.