Reading audio stream data from internet radio and pushing it to temporary file

Question

I'm in the process of setting up an audio processor on my remotely hosted CentOS box. The audio processor itself is command line based, and after speaking with the author he explained to me that it works by reading in a live .WAV stream, and it outputs a live .WAV too.

Now basically, the scenario I have is this:

I have a shoutcast server on this box using port 8000. This shoutcast server is the point at which the DJ's connect.

I have a secondary shoutcast server using port 8002 where the listeners will connect.

In between these, I would like to use this audio processing tool. It would need to connect to the first shoutcast server on port 8000, process the audio, and then send it to the server on port 8002.

The program cannot do this on it's own unfortunately, so I am told by the software author. He also stated that this scenario is workable, providing I use the right method. He suggested something like the following:

1. Command line tool that reads the incoming stream, and pipes it to:
2. Command line tool that extracts the MP3 data to WAV format, for example lame with option --decode.
3. Stereo Tool.
4. Program that encodes WAV to MP3 data, for example lame.
5. Program that streams this, which can handle a pipe as input.

Step 1+2 could be replaced by: 'arecord', linked using 'jack' to a program that receives and plays an incoming stream

Similarly, step 5 could be replaced by: 'aplayer', linked using 'jack' to a program that streams audio data.

I do understand what he has said, and I could proably do this if I was using a local install with a GUI and a sound card.

It's mainly the input and output im struggling with.

Answer 1

I haven't done this before nor tested it nor have thoroughly read the appropriate documentation. And I am not an expert in audio/video codecs and stuff. So this is more of a "this could work" guide and hopefully others can elaborate.

I did a quick search on google, trying to find out some tools that will cover the requirements (only command line tools).

1. Getting the audio stream from the first server: icecream
2. Decoding from mp3 to wav: lame
3. Your Stereo Tool: stereo_tool (hypothetically)
4. Encoding from wav to mp3: lame
5. Forwarding audio to the second server: ezstream

Assuming that your shoutcast servers are up and running in the same box. We will make a shell script stream2stream.sh that will read from the first, process and forward to the second.

$ chmod 750 stream2stream.sh
$ cat stream2stream.sh
#!/bin/bash

icecream --stdout http://localhost:8000 | \
lame -decode - - | \
stereo_tool | \
lame --preset cbr 128 -r -s 44.1 --bitwidth 16 - - | \
ezstream -c ~/ezstream.xml

Note that ezstream supports re-encoding by letting you define your own encoding/decoding programs. So my script above may be unnecessary and ezstream may be sufficient by itself. But I'm not familiar with this tool and so in this implementation we have the simplest configuration.

$ cat ~/ezstream.xml
<ezstream>
    <url>http://localhost:8002</url>
    <sourcepassword>hackme</sourcepassword>
    <format>MP3</format>
    <filename>stdin</filename>
    <stream_once>1</stream_once>

    <svrinfoname>My Stream</svrinfoname>
    <svrinfourl>http://yoursiteurl/</svrinfourl>
    <svrinfogenre>YourGenre</svrinfogenre>
    <svrinfodescription>This is a stream description</svrinfodescription>
    <svrinfobitrate>128</svrinfobitrate>
    <svrinfoquality>2.0</svrinfoquality>
    <svrinfochannels>2</svrinfochannels>
    <svrinfosamplerate>44100</svrinfosamplerate>
    <!-- Disallow the server to advertise the stream on a public YP directory: -->
    <svrinfopublic>0</svrinfopublic>
</ezstream>

You will have to adjust the parameters on lame and ezstream to your likings. You can execute the script with nohup or in screen.

screen -AmdS stereotool stream2stream.sh