Play .wav audio file via system bus.
Based on the work of https://github.com/fulldecent/system-bus-radio
We make use of Pulse Density Modulation (PDM) (see https://en.wikipedia.org/wiki/Pulse-density_modulation for more information). The Pulse Code Modulation (PCM) data from a .wav file is converted to a PDM bit stream.
Each PDM bit, is output at the same sample rate as the audio. If we see a bit with a value of 1, we make use of the _mm_stream_si128 instructions, otherwise we simply use a busy-wait loop. We perform each of these operations for a duration of 1/samplerate seconds.
You simply use sox to convert your audio to a high sample rate such as 1MHz, as seen below (This high rate is necessary for PDM).
make sox in.wav -r 1000000 out.wav ./musicplayer out.wav
- libsndfile - http://www.mega-nerd.com/libsndfile/