apt-X Lossless

White Paper








apt-X Lossless
a technical white paper
by Dr. David Trainor, APTX
www.aptx.com










1 | © APT Licensing Ltd., 2009 White Paper
INTRODUCTION
There exist numerous schemes - the results of development activity over many years in both the
academic and commercial fields, and within the wider open source community - for the so-called
lossless compression of digital audio. These schemes, which include, for example, Apple Lossless
[1], Free Lossless Audio Codec (aka FLAC) [2], and recently, mp3HD [3], are typically applied to gain
useful economies through the data reduction ("compression") in the bulk size of archived audio
files (mainly music, but also speech) held in storage on, usually, a computer hard-disk drive (HDD),
dedicated file server, or on solid-state memory device (e.g., Flash memory) and other portable
mass-storage systems, including read/writeable optical media (CD-ROM, DVD, DVD-HD, Blue-ray,
etc). These various formats are described and compared elsewhere [4].

This technology white paper introduces the reader to an entirely new scheme for lossless audio
compression called apt-X Lossless. This scheme has been conceived, designed and developed by
APTX, a pioneering audio processing technology company, the commercial originator of the apt-X
low-latency audio codec, and a venture-funded, private company with a long and profitable
association with both the broadcast industry and the studio post production business [5]. Briefly
and simply, by employing dynamic adaptation techniques to a greater and more intelligent extent
than conventional schemes, apt-X Lossless, offers significant benefits over existing lossless audio
codecs, and attains better coding scalability and run-time trade-offs as a result. These benefits are
of considerable importance to strongly emerging applications for high-definition forms of digital
entertainment, especially those deployed in the wirelessly networked, broadband home, and those
portable systems being developed for consumers on the move.

The applications of apt-X Lossless are not limited to broadcast digital TV and radio, but encompass
multi-channel/multi-program audio for high-def video-on-demand, and new forms of immersive,
multimedia entertainments, such as massively multi-player on-line games. APTX positions the apt-
X Lossless solutions as the organic continuation of a series of low-latency, predictive audio codecs
sharing the apt-X branding, starting with Standard apt-X, Enhanced apt-X and apt-X Live.

apt-X Lossless will be joined by another compression scheme - apt-X Scalable - a versatile
architecture with universal application across different processor platforms, variegated data
bandwidth conditions, energy budget, sonic fidelity and time-latency.
2 | © APT Licensing Ltd., 2009 White Paper
TECHNOLOGY OVERVIEW AND FEATURES
apt-X Lossless is an audio codec developed by APTX (APT Licensing Ltd.) for the lossless
compression of digital audio (including music, natural and synthetic speech, etc). A 16-bit, 48 kHz
stereo audio stream processed using apt-X Lossless typically compresses to about 55% of its
original average bit-rate, even for real-time audio streaming where low coding latency, low
computational complexity and high tolerance to communication errors is important. Short-term
compressed data rates for this type of stream typically fluctuate in the range of 500-900 kbps.

Note: the degree of compression achievable with purely lossless coding is heavily dependent on the
nature of the audio material, hence average compression rates are quoted with respect to a large
test suite of varied audio tracks, including music of various genres and speech in various languages.

apt-X Lossless supports high-definition audio up to 96 kHz sampling rates and sample resolutions
up to 24 bits. The codec optionally permits a "hybrid" coding scheme for applications where
average and/or peak com... [download for more]