BBB Audio Decoder

BBB Audio Decoder build

Introduction

In DIY audio, it's always been hard to use modern digital audio. You often need the signal chain to be analogue to make use of your own cross-overs, equalizers, etc. Decoders for digital audio that offer line-level outputs are usually very expensive, and let's face it, less fun. So, what started as a hopeful experiment came to fruition because of the very well featured multi-channel audio serial port of the Beagle Bone Black.

This project takes any signal into an optical TOSLINK, and either feeds it directly to the output in the case of PCM, or uses FFmpeg to auto-detect what it is, and decode into the 7.1 analogue outputs. The optical receiver chip is a DIR9001, and the output DAC is a PCM1690, all interfaced with I²S.

Of course, HDCP exists to sabotage it, because HDMI sources connected to my TV are output as raw PCM, but at least it works for the apps on my TV. More experimentation and research on that is required though, because from what I read, a fair amount of TVs are supposed to be able to pass-through the original bitstream, even to the optical output.

More text and instructions are to follow, especially if you want to compile the software.

Design files