avioflow 0.5.3

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

AvioFlow is packaged for several runtime and application environments. The native core is shared across bindings, so behavior stays consistent whether you embed it in a C++ service, call it from Python or JavaScript, ship it in a JVM application, or run it in WebAssembly.

Language / Runtime	Integration	Install / Consume	Compatibility
C++	Native CMake package	find_package(avioflow CONFIG REQUIRED)	Shared/static packages for Linux, macOS, and Windows; Linux packages include both libstdc++ ABI 0 and ABI 1 variants
Python	pybind11 binding	pip install avioflow	Wheels for mainstream desktop/server platforms
JavaScript / Node.js	Node-API native addon	npm install avioflow	Platform-specific native packages selected by npm
Java	JNI binding	Gradle / Maven	Runtime classifiers for Linux, macOS, and Windows
WebAssembly	WASM build	npm package / web bundle	Browser and WASM-capable runtime support

Decoder API Flow

AvioFlow uses the same pull-style output functions for offline and streaming decoding. The difference is only how input bytes enter the decoder.

Offline Input

+-----------------------+
| AudioDecoder(options) |
+-----------+-----------+
            |
            v
+-----------------------------+
| load_file(path)             |
| load_buffer(bytes, size)    |
+-----------+-----------------+
            |
            v
+-----------------------------+
| get_frame()                 |  one decoded frame, zero-copy
| get_samples()               |  all currently available samples
+-----------+-----------------+
            |
            v
+-----------------------------+
| is_finished()               |
+-----------------------------+

Streaming Input

+--------------------------------------+
| AudioDecoder(input_format, rate, ch) |
+-----------+--------------------------+
            |
            v
+-----------------------------+
| feed(chunk)                 |  first feed starts stream mode
+-----------+-----------------+
            |
            v
+-----------------------------+
| get_frame()                 |  returns empty if data is incomplete
| get_samples()               |  drains currently available samples
+-----------+-----------------+
            | repeat feed/get_* while streaming
            v
+-----------------------------+
| flush()                     |  no more input; drain decoder delay
+-----------+-----------------+
            |
            v
+-----------------------------+
| get_samples() / get_frame() |  drain until is_finished()
+-----------------------------+

flush() does not discard data. It marks stream input complete so remaining buffered bytes and codec-delayed frames can be drained.

Installation

Python

pip install avioflow

Java

Gradle users need the main Java API jar plus one native classifier for the target platform:

dependencies {
    implementation("io.github.lxp3:avioflow:0.5.3")
    runtimeOnly("io.github.lxp3:avioflow:0.5.3:linux-x86_64")
}

Maven:

<dependency>
  <groupId>io.github.lxp3</groupId>
  <artifactId>avioflow</artifactId>
  <version>0.3.2</version>
</dependency>
<dependency>
  <groupId>io.github.lxp3</groupId>
  <artifactId>avioflow</artifactId>
  <version>0.3.2</version>
  <classifier>linux-x86_64</classifier>
  <scope>runtime</scope>
</dependency>

Native classifiers: linux-x86_64, linux-aarch64, macos-x86_64, macos-aarch64, windows-x86_64, windows-aarch64.

C++ (CMake)

Download the C++ package for your platform and linkage, then point CMake at the extracted package root with CMAKE_PREFIX_PATH.

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

Release packages are split by linkage and platform:

Linux binaries target glibc 2.28 or newer. Select ABI 0 for the legacy libstdc++ string ABI or ABI 1 for the C++11 string ABI; the eight Linux C++ archives use the filenames avioflow-{shared|static}-linux-{x64|arm64}-abi{0|1}.tar.gz.

• avioflow-shared-linux-x64-abi1, avioflow-shared-linux-x64-abi0
• avioflow-static-linux-x64-abi1, avioflow-static-linux-x64-abi0
• avioflow-shared-linux-arm64-abi1, avioflow-shared-linux-arm64-abi0
• avioflow-static-linux-arm64-abi1, avioflow-static-linux-arm64-abi0
• avioflow-shared-macos-x64, avioflow-static-macos-x64
• avioflow-shared-macos-arm64, avioflow-static-macos-arm64
• avioflow-shared-win-x64, avioflow-static-win-x64
• avioflow-shared-win-arm64, avioflow-static-win-arm64

Shared packages include the FFmpeg dynamic libraries needed at runtime. Static packages include FFmpeg static libraries, transitive static dependency metadata, and the bundled FFmpeg CMake package, so consumers do not need to configure FFmpeg separately.

---

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
load_file(source)	Load file path, URL, or device and return metadata
load_buffer(data, size)	Load complete audio bytes from memory
feed(data, size)	Feed stream bytes; first feed starts stream mode
flush()	Mark stream input complete and allow draining
get_frame()	Decode next frame, returns FrameData
get_samples()	Drain currently available samples
get_metadata()	Get audio metadata
is_finished()	Check if EOF reached

FrameData

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

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 get_frame() or get_samples() call.

Examples

File Decoding (Offline)

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

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

Raw PCM Memory Decode

// Raw PCM bytes have no container/header, so provide the input format details.
// Use FFmpeg demuxer format names such as "s16le", not codec names like
// "pcm_s16le".
AudioStreamOptions opts;
opts.input_format = "s16le";       // Signed 16-bit little-endian PCM
opts.input_sample_rate = 8000;     // 8 kHz
opts.input_channels = 1;           // Mono

AudioDecoder decoder(opts);
decoder.load_buffer(pcm_bytes, pcm_size); // Full PCM buffer in memory

while (auto frame = decoder.get_frame()) {
    // Output samples are float planar: frame.data[channel][sample]
    process(frame.data[0], 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.feed(raw_bytes, size);  // First feed starts stream mode

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

---

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_file(source)	Metadata	Load file, URL, or pathlib.Path
load_buffer(data)	Metadata	Load complete bytes-like input
feed(data)	None	Feed streaming bytes
flush()	None	Mark stream input complete
get_frame()	ndarray | None	Decode next frame
get_samples()	ndarray	Drain currently 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_file("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)
    if not data:
        decoder.flush()
        break
    decoder.feed(data)
    samples = decoder.get_samples()
    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
loadFile(source)	Metadata	Load file, URL, or device name. Returns metadata.
loadBuffer(buffer)	Metadata	Load complete encoded bytes from memory.
feed(buffer)	void	Feed streaming bytes.
flush()	void	Mark stream input complete.
getFrame()	Float32Array[] | null	Decode next frame. Returns array of channel data.
getSamples()	Float32Array[]	Drain currently available samples.
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.loadFile("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.feed(chunk);

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

socket.on('end', () => {
    decoder.flush();
    const remaining = decoder.getSamples();
    if (remaining.length > 0) {
        processAudio(remaining);
    }
});

Device Discovery

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

---

Java API

File Decoding

import io.github.lxp3.avioflow.AudioDecoder;
import io.github.lxp3.avioflow.AudioStreamOptions;

try (AudioDecoder decoder = new AudioDecoder(
        new AudioStreamOptions().outputSampleRate(16000))) {
    decoder.loadFile("audio.mp3");
    float[][] samples = decoder.getSamples();
    System.out.println(samples.length + " channels");
}

Encoding

import io.github.lxp3.avioflow.AudioEncoder;
import io.github.lxp3.avioflow.AudioWriteOptions;

AudioEncoder.saveAudio(
    "out.wav",
    samples,
    new AudioWriteOptions()
        .containerFormat("wav")
        .codecName("pcm_s16le")
        .sampleRate(16000)
);

---

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.

Java Build

./build-java.sh linux-x86_64

This builds the JNI library and creates a platform classifier jar.

---

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