Transcribe streaming audio from a microphone in Ruby

1
require 'websocket-client-simple'
2
require 'json'
3
require 'open3'
4
5
API_KEY = "<YOUR_API_KEY>"
6
SAMPLE_RATE = 16000
7
CHANNELS = 1
8
CHUNK_SIZE = 6400 # 200ms of audio at 16kHz = 3200 samples = 6400 bytes (16-bit = 2 bytes per sample)
9
10
$recording = false
11
$sox_process = nil
12
$stdout_thread = nil
13
$exit_requested = false
14
15
ws = WebSocket::Client::Simple.connect(
16
  "wss://api.assemblyai.com/v2/realtime/ws?sample_rate=#{SAMPLE_RATE}",
17
  headers: { 'Authorization' => API_KEY }
18
)
19
20
ws.on :open do
21
  on_open(ws)
22
end
23
24
ws.on :message do |message|
25
  on_message(ws, message.data)
26
end
27
28
ws.on :error do |error|
29
  on_error(ws, error)
30
end
31
32
ws.on :close do |code, reason|
33
  on_close(ws, code, reason)
34
end
35
36
def on_open(ws)
37
  begin
38
    command = "sox -d -t raw -b 16 -c #{CHANNELS} -r #{SAMPLE_RATE} -e signed-integer -L -"
39
    $sox_process, stdout, stderr, wait_thr = Open3.popen3(command)
40
    puts "Started audio recording with SoX"
41
    
42
    $recording = true
43
    
44
    $stdout_thread = Thread.new do
45
      while $recording && ws.open?
46
        begin
47
          audio_data = stdout.read_nonblock(CHUNK_SIZE)
48
          if audio_data && !audio_data.empty?
49
            audio_message = {
50
                "audio_data" => audio_data.bytes
51
            }.to_json
52
            ws.send(audio_message)
53
          end
54
        rescue IO::WaitReadable
55
          sleep 0.01
56
        rescue EOFError
57
          puts "Audio stream ended"
58
          break
59
        end
60
      end
61
    end
62
  rescue => e
63
    puts "Error starting audio recording: #{e}"
64
    puts e.backtrace
65
  end
66
end
67
68
def on_message(ws, message)
69
  begin
70
    msg = JSON.parse(message)
71
    msg_type = msg['message_type']
72
    
73
    if msg_type == 'SessionBegins'
74
      session_id = msg['session_id']
75
      puts "Session ID: #{session_id}"
76
      return
77
    end
78
    
79
    text = msg['text'] || ''
80
    return if text.empty?
81
    
82
    if msg_type == 'PartialTranscript'
83
      puts "Partial: #{text}"
84
    elsif msg_type == 'FinalTranscript'
85
      puts "Final: #{text}"
86
    elsif msg_type == 'error'
87
      puts "Error: #{msg['error'] || 'Unknown error'}"
88
    end
89
  rescue => e
90
    puts "Error handling message: #{e.message}"
91
    puts "Raw message: #{message.inspect}"
92
  end
93
end
94
95
def on_error(ws, error)
96
  puts "Error: #{error}"
97
end
98
99
def on_close(ws, code, reason)
100
  stop_recording
101
  puts 'Disconnected'
102
end
103
104
def stop_recording
105
  if $recording
106
    $recording = false
107
    
108
    if $sox_process
109
      begin
110
        Process.kill('TERM', $sox_process.pid) rescue nil
111
        $sox_process.close
112
        $stdout_thread.join(2) if $stdout_thread
113
        puts "Stopped audio recording"
114
      rescue => e
115
        puts "Error closing audio recording: #{e}"
116
      end
117
    end
118
  end
119
end
120
121
Signal.trap('INT') do
122
  puts
123
  puts 'Stopping recording'
124
  stop_recording
125
  puts 'Closing real-time transcript connection'
126
  $exit_requested = true
127
end
128
129
loop do
130
  if $exit_requested
131
    ws.close if ws.open?
132
    break
133
  end
134
  sleep 1
135
end