Skype Technologies S.A. Skype Technologies S.A. Skype Technologies S.A. This document describes SILK, a speech codec for real-time, packet- based voice communications. Targeting a diverse range of operating environments, SILK provides scalability in several dimensions. Four different sampling frequencies are supported for encoding the audio input signal. Adaptation to network characteristics is provided through control of bitrate, packet rate, packet loss resilience and use of discontinuous transmission (DTX). And several different complexity levels let SILK take advantage of available processing power without relying on it. Each of these properties can be adjusted during operation of the codec on a frame-by-frame basis.