ASR quickstart

ASR quickstart#

This tutorial takes you from a fresh installation to a running transcript. By the end you will have a Python script that streams audio from your microphone and prints the transcribed text to stdout.

Prerequisites#

You need:

  • The ABR SDK: pip install abr-sdk

  • An ASR application package downloaded and extracted from the ABR developer portal. You should have a directory containing a .so shared library file.

  • arecord (from the alsa-utils package, included on most Linux distributions) to capture audio from your microphone.

  • A working microphone connected to your device.

  • An activated license for this device. See License activation.

If you have not downloaded a package yet, follow Installation first.

Write the script#

Now we’ll write a script that streams audio from your microphone and prints the transcribed text to stdout.

Create a file called microphone.py:

import sys
from abr_sdk.asr import Asr, AsrChunk

LIBRARY_PATH = "/path/to/niagara-38m-live.en/libniagara_38m_live.so"
CHUNK_BYTES = 16000 * 2 // 10  # 100 ms of 16 kHz mono S16_LE audio

buf = bytearray()

def on_chunk(chunk: AsrChunk) -> None:
    chunk.update(buf)
    print(f"\r{buf.decode('utf-8')}", end="", flush=True)

with Asr(LIBRARY_PATH) as asr:
    print("Listening... press Ctrl+C to stop.", flush=True)
    try:
        while chunk := sys.stdin.buffer.read(CHUNK_BYTES):
            asr.push(chunk, on_chunk=on_chunk)
    except KeyboardInterrupt:
        pass
    asr.wait_for_completion()

print()

Set LIBRARY_PATH to the absolute path of the .so file inside your extracted package directory. For example, the niagara-38m-live.en package contains libniagara_38m_live.so.

Run it#

arecord -f S16_LE -c 1 -r 16000 -t raw -q | python microphone.py

Speak into your microphone, then press Ctrl+C to stop. The final transcript is printed to stdout.

What just happened#

arecord -f S16_LE -c 1 -r 16000 -t raw -q captures raw 16-bit mono PCM at 16 kHz, the format the ASR model expects, and pipes it to the script’s standard input.

sys.stdin.buffer.read(CHUNK_BYTES) pulls the next 100 ms of audio from the pipe. The loop ends when arecord stops and the pipe closes.

CHUNK_BYTES = 16000 * 2 // 10 is 100 milliseconds of audio per push call (16,000 samples per second × 2 bytes per sample ÷ 10). The model does not require a specific chunk size; smaller chunks reduce latency.

on_chunk / chunk.update(buf) applies each text chunk to buf in place, including the overwrites that ACCURATE and post-processing passes emit, so the transcript refines on the same line as it is reprinted with \r.

asr.push(chunk, on_chunk=on_chunk) hands each audio chunk to the model. push() is non-blocking; it returns as soon as the input bytes are accepted.

asr.wait_for_completion() signals end-of-audio, flushes the model pipeline, and blocks until every pending text chunk has been delivered.

Next steps