EasyAACEncoder

EasyAACEncoder is a small C/C++ audio transcoding library that converts G.711 A-law, G.711 u-law, G.726, and raw PCM16 audio into AAC.

The project preserves the original EasyDarwin C API while using a modern C++23 implementation internally. FAAC is bundled for AAC encoding, and Kiss FFT is bundled through the FAAC source tree.

Features

• AAC output with ADTS headers.
• Input support for:
  • G.711 A-law
  • G.711 u-law
  • G.726 at 16, 24, 32, and 40 kbit/s
  • Raw 16-bit PCM
• Public C API suitable for C and C++ callers.
• Static and shared library builds.
• CMake-based build system.

Requirements

• CMake 3.20 or newer.
• A C++23 compiler for EasyAACEncoder and the bundled FAAC/Kiss FFT sources.
• Linux or another POSIX-like environment with pthread and libm.

Build

Configure and build:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

Generated artifacts are written to dist/:

• dist/libEasyAACEncoder.a
• dist/libEasyAACEncoder.so
• dist/easy_aac_encoder_sample

Useful targets:

cmake --build build --target static
cmake --build build --target shared
cmake --build build --target sample
cmake --build build --target warnings
cmake --build build --target fmt
cmake --build build --target clean-generated

The warnings target compiles project-owned C++23 sources with -Wall -Wextra -Werror. Bundled FAAC and Kiss FFT sources are also compiled as C++23 during normal builds, but are not forced through the project -Werror policy.

Sample Program

The sample executable is built as:

cmake --build build --target sample

Run it from the sample-data directory so relative input paths resolve:

cd examples/basic_transcoder
../../dist/easy_aac_encoder_sample

By default, the sample encodes playback.pcm to playback.aac. The same sample source also includes G.711 and G.726 examples.

Public API

include the public header:

#include "EasyAACEncoderAPI.h"

Basic flow:

InitParam init = {0};
init.ucAudioCodec = Law_PCM16;
init.ucAudioChannel = 1;
init.u32AudioSamplerate = 8000;
init.u32PCMBitSize = 16;

Easy_Handle encoder = Easy_AACEncoder_Init(init);
if (encoder == NULL) {
    /* handle init failure */
}

unsigned int out_len = 0;
int rc = Easy_AACEncoder_EncodeEx(
    encoder,
    input_data,
    input_size,
    output_data,
    output_capacity,
    &out_len
);

Easy_AACEncoder_Release(encoder);

Prefer Easy_AACEncoder_EncodeEx for new code because it receives the output buffer capacity and can detect undersized buffers.

Easy_AACEncoder_Encode is still available for compatibility with existing callers, but it cannot verify the output buffer capacity.

Supported Codec Values

enum Law
{
    Law_ULaw = 0,
    Law_ALaw = 1,
    Law_PCM16 = 2,
    Law_G726 = 3
};

For G.726 input, set init.g726param.ucRateBits to one of:

enum Rate
{
    Rate16kBits = 2,
    Rate24kBits = 3,
    Rate32kBits = 4,
    Rate40kBits = 5
};

Repository Layout

• include/ - public API header.
• src/ - EasyAACEncoder implementation and codec wrappers.
• src/libfaac/ - bundled FAAC encoder sources.
• src/include/ - bundled FAAC public headers.
• src/libfaac/kiss_fft/ - bundled Kiss FFT sources used by FAAC.
• examples/basic_transcoder/ - sample program and sample input data.

Acknowledgements

EasyAACEncoder builds on work from:

• EasyDarwin, which organized and developed the original EasyAACEncoder library and API.
• FAAC, the Freeware Advanced Audio Coder used for AAC encoding.
• Kiss FFT, used by the bundled FAAC implementation.
• ITU-T G.711 and G.726 audio codec specifications.

Review the license notices in the bundled source files before redistributing modified builds.

More Information

Email: support@easydarwin.org

Website: www.EasyDarwin.org

Copyright (c) EasyDarwin.org 2012-2019 Copyright (c) 2026 Yehor Smoliakov