In a recent article I wrote about how I'd started to integrate more of my house's audio system with a networked audio protocol known as "VBAN". I'd gotten some great use out of the system, but I'd started running into some problems more recently...

You see, for some reason, if I were streaming some audio to my Raspberry Pi, and the stream dropped into a lull (i.e. between songs, say) I'd often see some pretty nasty buffer errors from Alsa. Now, I could've dug into it much deeper and tried to get to the root of the problem in C, but I didn't really feel like it. Instead, I thought I'd just throw some Python at it! So after spending an intermittent afternoon reminding myself how the subprocess module works, and debugging my own madness, I got a working script that I use as a systemd service.

# VBAN Receiver in Python

# Imports
import subprocess

# Executor Function
def execute(cmd):
    popen = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT, universal_newlines=True)
    while True:
        for stdout_line in iter(popen.stdout.readline, ""):
            yield stdout_line, popen
    popen.stdout.close()
    return_code = popen.wait()
    if return_code:
        raise subprocess.CalledProcessError(return_code, cmd)

# Define Attributes
MASTER_PC_IP = "<your-ip-here>"
LOG_FILE = '/var/vban_log.log'

# Define Command and Args
EXECUTABLE = "/usr/local/bin/vban_receptor"
ARGS = ["-i", MASTER_PC_IP, "-p", "6980", "-s", "StereoPi", "-d", "front", "-q", "0"]

CALL = [EXECUTABLE]
CALL.extend(ARGS)

# Call the System
while True:
    with open(LOG_FILE, 'a') as logFile:
        for output, proc_handle in execute(CALL):
            print(output, end='')
            logFile.write(output)
            # Catch Error
            if "Error: alsa_write:" in output:
                print("Failure... Python intervening!")
                proc_handle.kill()
                proc_handle.wait()
                break # Continue While Loop - Call Again
# END

With that magic little Python script, I basically kick VBAN in the butt every time that Alsa decides to be unfriendly (which happens quite regularly) by killing the process, and then starting it right back up. With the magic of computers, this happens very fast, and as I'd briefly mentioned earlier, it only seems to really play into the "mix" in-between songs anyway. So after building the script, giving it a nice little test drive, and scrutinizing my Raspberry Pi; I thought it was time to build it back into my simple little service.

# /etc/systemd/system/vbanstereorx.service
# vbanstereorx.service
# VBAN Receptor Stereo Service

[Unit]
Description= VBAN Stereo Receptor

[Service]
Type=simple
ExecStart=/usr/bin/python3 /home/vbanner.py
Restart=always

[Install]
WantedBy=multi-user.target

I'm sure I'll be back to crack the hood back open on this one at some point, but for now, I'm happy to stream my music back to my cabinet stereo with the power of Linux.