avioflow 0.3.0

High-performance audio decoding with FFmpeg and C++

AvioFlow

AvioFlow is a high-performance and easy-to-use streaming audio decoding library.

Features

• Audio format: mp3, opus, flac, ogg, wav, m4a, acc. Anything.
• Flexible Input: Files, URLs, memory buffers, and real-time streams
• Hardware Capture: WASAPI loopback (system audio) and DirectShow (microphones)
• Resampling: Built-in sample rate conversion
• Zero-copy API: Direct buffer access via FrameData for maximum performance
• Cross-platform: Windows, Linux, macOS

Supported language

C++
python	pybind11	pip install avioflow
JavaScript	node-add-api	npm install avioflow
	wasm
	vsix

Installation

Python

pip install avioflow

C++ (CMake)

find_package(avioflow REQUIRED)
target_link_libraries(your_target avioflow::avioflow)

---

C++ API

Core Classes

AudioDecoder

Main class for audio decoding.

#include "avioflow-cxx-api.h"
using namespace avioflow;

// Constructor options
AudioStreamOptions options;
options.output_sample_rate = 16000;    // Target sample rate
options.input_format = "s16le";        // For streaming: source format
options.input_sample_rate = 48000;     // For streaming: source rate
options.input_channels = 2;            // For streaming: source channels

AudioDecoder decoder(options);

Methods

Method	Description
open(source)	Open file path, URL, or device
push(data, size)	Push raw bytes for streaming decode
read()	Decode next frame, returns FrameData. (Formerly decode_next)
get_samples()	Decode all currently available samples. (Formerly get_samples)
get_metadata()	Get audio metadata
is_finished()	Check if EOF reached

FrameData

Zero-copy frame data structure returned by read().

struct FrameData {
    float** data;        // Planar channel pointers: data[channel][sample]
    int num_channels;    // Number of channels
    int num_samples;     // Samples per channel

    operator bool();     // True if valid data
};

⚠️ Warning: FrameData.data points to internal buffer, valid only until next read() call.

Examples

File Decoding (Offline)

AudioDecoder decoder({.output_sample_rate = 16000});
decoder.open("audio.mp3");

auto samples = decoder.get_samples();  // vector<vector<float>>
std::cout << "Channels: " << samples.size() << std::endl;
std::cout << "Samples: " << samples[0].size() << std::endl;

Frame-by-Frame Decoding

AudioDecoder decoder;
decoder.open("audio.mp3");

while (auto frame = decoder.read()) {
    // frame.data[channel][sample]
    for (int c = 0; c < frame.num_channels; c++) {
        process(frame.data[c], frame.num_samples);
    }
}

Streaming Decode (Push-based)

AudioStreamOptions opts;
opts.input_format = "s16le";
opts.input_sample_rate = 48000;
opts.input_channels = 2;

AudioDecoder decoder(opts);
decoder.push(raw_bytes, size);  // Auto-initializes on first call

auto samples = decoder.get_samples(); // Decode all buffered data
// Or frame-by-frame:
while (auto frame = decoder.read()) {
    // Process decoded audio...
}

---

Python API

AudioDecoder

import avioflow

# Constructor with keyword arguments
decoder = avioflow.AudioDecoder(
    output_sample_rate=16000,    # Optional: target sample rate
    input_format="s16le",        # For streaming: source format
    input_sample_rate=48000,     # For streaming: source rate
    input_channels=2             # For streaming: source channels
)

Methods

Method	Returns	Description
load(source)	Metadata	Load file, URL, pathlib.Path, or bytes-like input
decoder(data)	ndarray	Push bytes-like data and decode (streaming)
read()	ndarray	Decode next frame
get_samples()	ndarray	Decode all available samples
is_finished()	bool	Check if EOF

Metadata

# Quick metadata inspection without full decoding
meta = avioflow.info("audio.mp3")
print(f"Duration: {meta.duration}s")
print(f"Sample Rate: {meta.sample_rate}Hz")
print(f"Codec: {meta.codec}")

# Encoded audio bytes also work
with open("audio.mp3", "rb") as f:
    meta = avioflow.info(f.read())

Examples

File Decoding

decoder = avioflow.AudioDecoder(output_sample_rate=16000)
meta = decoder.load("speech.wav")
samples = decoder.get_samples()      # numpy array (channels, samples)
print(f"Shape: {samples.shape}")     # e.g., (1, 160000)

Streaming Decode

decoder = avioflow.AudioDecoder(
    input_format="s16le",
    input_sample_rate=48000,
    input_channels=2
)

while True:
    data = socket.recv(4096)
    samples = decoder(data)  # Push & get samples in one call
    if samples.size > 0:
        process_audio(samples)

Device Discovery

devices = avioflow.DeviceManager.list_audio_devices()
for dev in devices:
    print(f"{dev.name}: {dev.description}")

Logging

avioflow.set_log_level("debug")  # quiet, error, warning, info, debug, trace

---

Node.js API

Compatibility

Runtime	Version	Support
Node.js	16, 18, 20, 22+	✅ Native (N-API)
Electron	All versions	✅ Supported (requires rebuild)
Architectures	x64	✅ Linux, Windows

Installation

npm install avioflow

ESM Import

import avioflow from 'avioflow';

Module-level Functions

Function	Returns	Description
load(path, options?)	{metadata, samples}	Convenience: Opens, decodes all samples, and returns both in one call.
listAudioDevices()	DeviceInfo[]	List available system audio devices.
setLogLevel(level)	void	Set FFmpeg log level ("quiet", "info", "debug", etc.).

AudioDecoder

// Constructor with options object
const decoder = new avioflow.AudioDecoder({
    outputSampleRate: 16000,    // Optional: target sample rate
    outputNumChannels: 1,       // Optional: target channels
    inputFormat: 's16le',       // For streaming: source format
    inputSampleRate: 48000,     // For streaming: source rate
    inputChannels: 2            // For streaming: source channels
});

Methods

Method	Returns	Description
load(source)	Metadata	Load file, URL, or device name. Returns metadata.
push(buffer)	void	Push raw encoded bytes for streaming.
read()	Float32Array[] | null	Decode next frame. Returns array of channel data.
getSamples()	Float32Array[]	Decode all available samples at once.
isFinished()	boolean	Check if end of stream reached.

Examples

Quick File Loading (Recommended)

// Opens file, resamples to 16kHz mono, and decodes everything
const { metadata, samples } = avioflow.load("audio.mp3", {
    outputSampleRate: 16000,
    outputNumChannels: 1
});

console.log(`Duration: ${metadata.duration}s`);
console.log(`Channels: ${samples.length}, Samples: ${samples[0].length}`);

Batch Decoding with Decoder Instance

const decoder = new avioflow.AudioDecoder({ outputSampleRate: 44100 });
const meta = decoder.load("audio.wav");

// Decodes the entire file into memory
const allSamples = decoder.getSamples();
process(allSamples);

Streaming Decode (Real-time)

const decoder = new avioflow.AudioDecoder({
    inputFormat: 's16le',
    inputSampleRate: 48000,
    inputChannels: 2
});

socket.on('data', (chunk) => {
    decoder.push(chunk);

    // Get all samples decoded from this chunk
    const samples = decoder.getSamples();
    if (samples.length > 0) {
        processAudio(samples);
    }
});

Device Discovery

const devices = avioflow.listAudioDevices();
devices.forEach(dev => {
    console.log(`${dev.isOutput ? 'Output' : 'Input'}: ${dev.name} (${dev.description})`);
});

---

Build from Source

Prerequisites

• CMake 3.20+
• Visual Studio 2022+ (Windows) or GCC 11+ (Linux)
• Python 3.8+ with pybind11 (for Python bindings)
• Node.js 16+ (for Node.js bindings)

C++ & Python Build

./build.sh

This will configure and build the C++ library and Python bindings.

Node.js Build

./build-nodejs.sh

This will build the Node.js bindings using cmake-js and run compatibility tests.

---

Supported Formats

AvioFlow supports a wide range of audio formats, codecs, and devices through FFmpeg.

For a complete and detailed list of supported decoders, encoders, and input formats, please refer to the Supported Formats Reference.

---

License

MIT License