Audio compression with EnCodec and OpenVINO

This tutorial is also available as a Jupyter notebook that can be cloned directly from GitHub. See the installation guide for instructions to run this tutorial locally on Windows, Linux or macOS.

Github

Compression is an important part of the Internet today because it enables people to easily share high-quality photos, listen to audio messages, stream their favorite shows, and so much more. Even when using today’s state-of-the-art techniques, enjoying these rich multimedia experiences requires a high speed Internet connection and plenty of storage space. AI helps to overcome these limitations: “Imagine listening to a friend’s audio message in an area with low connectivity and not having it stall or glitch.”

This tutorial considers ways to use OpenVINO and EnCodec algorithm for hyper compression of audio. EnCodec is a real-time, high-fidelity audio codec that uses AI to compress audio files without losing quality. It was introduced in High Fidelity Neural Audio Compression paper by Meta AI. The researchers claimed they achieved an approximate 10x compression rate without loss of quality and made it work for CD-quality audio. More details about this approach can be found in Meta AI blog and original repo.

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Prerequisites

Install required dependencies:

!python -W ignore -m pip install -q -r requirements.txt

Instantiate audio compression pipeline

Codecs, which act as encoders and decoders for streams of data, help empower most of the audio compression people currently use online. Some examples of commonly used codecs include MP3, Opus, and EVS. Classic codecs like these decompose the signal between different frequencies and encode as efficiently as possible. Most classic codecs leverage human hearing knowledge (psychoacoustics) but have a finite or given set of handcrafted ways to efficiently encode and decode the file. EnCodec, a neural network that is trained from end to end to reconstruct the input signal, was introduced as an attempt to overcome this limitation. It consists of three parts:

  • The encoder, which takes the uncompressed data in and transforms it into a higher dimensional and lower frame rate representation.

  • The quantizer, which compresses this representation to the target size. This compressed representation is what is stored on disk or will be sent through the network.

  • The decoder is the final step. It turns the compressed signal back into a waveform that is as similar as possible to the original. The key to lossless compression is to identify changes that will not be perceivable by humans, as perfect reconstruction is impossible at low bit rates.

encodec_compression

encodec_compression

The authors provide two multi-bandwidth models: * encodec_model_24khz - a causal model operating at 24 kHz on monophonic audio trained on a variety of audio data. * encodec_model_48khz - a non-causal model operating at 48 kHz on stereophonic audio trained on music-only data.

In this tutorial, we will use encodec_model_24khz as an example, but the same actions are also applicable to encodec_model_48khz model as well. To start working with this model, we need to instantiate model class using EncodecModel.encodec_model_24khz() and select required compression bandwidth among available: 1.5, 3, 6, 12 or 24 kbps for 24 kHz model and 3, 6, 12 and 24 kbps for 48 kHz model. We will use 6 kbs bandwidth.

from encodec import EncodecModel
from encodec.utils import convert_audio
import torchaudio
import torch

# Instantiate a pretrained EnCodec model
model = EncodecModel.encodec_model_24khz()
model.set_target_bandwidth(6.0)

Explore EnCodec pipeline

Let us explore model capabilities on example audio:

import sys
import librosa
import matplotlib.pyplot as plt
import librosa.display
import IPython.display as ipd

sys.path.append("../utils")

from notebook_utils import download_file

test_data_url = "https://github.com/facebookresearch/encodec/raw/main/test_24k.wav"

sample_file = 'test_24k.wav'
download_file(test_data_url, sample_file)
audio, sr = librosa.load(sample_file)
plt.figure(figsize=(14, 5))
librosa.display.waveshow(audio, sr=sr)

ipd.Audio(sample_file)

test_24k.wav:   0%|          | 0.00/938k [00:00<?, ?B/s]