This is a daemon and companion website to stream audio. I use it to stream from
my system's audio to an
<audio> element. It outputs MP3 audio.
I thought it would be fun to be able to share what I am playing on my local
media player on a simple website. I wanted to take the audio directly from
PulseAudio and make it available in an
To do this, I've written a C library to read/decode audio from PulseAudio and then encode/write it out as MP3. I use the library in Go with cgo.
Essentially this gives me a simple daemon I can start that will livestream my system's audio.
- ffmpeg (libavcodec, libavformat, libavdevice, libavutil, libswresample). I developed using 3.2.2. On Debian this is in the package libavutil-dev.
- C compiler. I developed using gcc 6.2.1.
- Go. I developed using 1.7.3.
- The track display feature depends on accessing a song_tracker API. This is optional however.
- go get github.com/horgh/audiostreamer
- go build
- Place index.html somewhere accessible. Update the
<audio>element src attribute. If you don't want to use the song tracker, then set
song_tracker_urlto a blank string.
- Run the daemon. Its usage output shows the possible flags. There is no configuration file.
- audiostreamer: A Go daemon that serves HTTP requests to stream audio as MP3.
- audiostreamer.h: A library that uses ffmpeg to read/decode from PulseAudio and encode/write to MP3.
- index.html: A website containing an
<audio>element that lets us stream audio from the daemon. It also displays the currently playing track (by polling a song_tracker API). In the case of daemon restart, clients try to reconnect endlessly.
- transcode_example: A sample C program that uses audiostreamer.h to transcode to a file.
- In general MP3 is not a streamable format. To make it possible to slice and start streaming from anywhere (if an encode is already in progress), I disable the MP3 bit reservoir. This means I can have just one encoded stream for any number of streaming clients.
- In theory output can be any audio format/codec. In a few places I have
hardcoded use of MP3. To switch to a different output format/codec, it is
likely sufficient to change the
encoder(), and adjust the
audioRequest(). You must make sure the format/codec is streamable and that it is valid to send audio frames starting from any point, as that is the current behaviour.
- In theory input can be from a file. In fact this does work, for a given value of work. Right now the daemon decodes as quickly as it can. When taken from a PulseAudio input the daemon is throttled as the audio is real time. From a file however there is no such limit, and it will consume 100% CPU (one thread). As well, it decodes the same file over and over. As my main use case is to stream from PulseAudio I have chosen to leave this as is as adjusting it introduces complexity.