Detects the built-in play/pause button on wired earbuds/headsets by monitoring the microphone.

headset_buttons.py

#!/usr/bin/env python3
#
# Detects the built-in play/pause button on wired earbuds/headsets by
# monitoring the microphone.
#
# The script outputs a line containing either "press" or "release" whenever
# a press or release is detected.
#
# This script works by detecting a period of high (near maximum) sample values
# followed quickly by a period of low (near minimum) sample values, or vice
# versa. Low -> high corresponds to a press, high -> low corresponds to a
# release. At least according to my testing, YMMV.


CHUNK = 1024
HIST_SIZE = 64

import pyaudio;

audio = pyaudio.PyAudio();
info = audio.get_default_input_device_info()
stream = audio.open(
        input=True,
        rate=int(info['defaultSampleRate']),
        channels=1,
        format=pyaudio.paInt16)

hi_lo_history = [0] * HIST_SIZE # -1 = low, 1 = high
hist_idx = 0

try:
    while True:

        frames = stream.read(CHUNK);

        all_high = True # All samples exceed 32000
        all_low = True # All samples exceed -32000
        for frame_idx in range(CHUNK):
            sample = 0
            if frames[2*frame_idx + 1]>>7 == 1:
                sample = -1 ^ 65535

            sample |= frames[2*frame_idx] | (frames[2*frame_idx + 1] << 8)

            if sample < 32000:
                all_high = False
            if sample > -32000:
                all_low = False

        if -1 in hi_lo_history and all_high:
            print("press", flush=True)
            hi_lo_history = [0] * HIST_SIZE

        if 1 in hi_lo_history and all_low:
            print("release", flush=True)
            hi_lo_history = [0] * HIST_SIZE

        if all_high:
            hilo = 1
        elif all_low:
            hilo = -1
        else:
            hilo = 0

        hi_lo_history[hist_idx] = hilo
        hist_idx = (hist_idx + 1) % HIST_SIZE;

except KeyboardInterrupt:
    pass