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Knowledge Structures for Encoding, Formatting, and Packaging
Published in Denise Bedford, Knowledge Architectures, 2020
We must also understand format compression because we are concerned about being able to access the knowledge kernel – whether it is a recorded interview, speech or memorandum, or a cultural performance funded by a community organization. Compression is essential to all kinds of formats, but mainly to audio file formats because it is a way to manage file size. Compression choices are typically made by network and technology architects to conserve storage space. Their decisions, though, can impact the knowledge architect’s ability to provide continuous availability to digital assets well into the future. Knowledge architects should understand the three types of compression, including (1) uncompressed audio (WAV, AIFF, AU or raw header-less PCM); (2) lossless compression files (FLAC, WavPack, TTA, ATRAC, ALAC, PGEG-4, MPEG-4ALS, MPEG-4DST, Windows Media Audio Lossless) and (3) lossy compression (i.e., Opus, MP3, Vorbis, Musepack, AAC, ATRAC, Windows Media Audio Lossy). Uncompressed audio is an audio file with no compression applied to it – the sound remains the same as when it was recorded. Lossless formats use compression algorithms that preserve audio data, so the audio is the same as the source. The lossy audio produces a lower-quality sound and has a smaller file size. Lossy compression produces a smaller file size and has a lower quality sound. It is called lossy because this approach to compression is not reversible – it is impossible to rebuild any elements that were stripped away. The encoding standards you choose will impact what is and is not available in the knowledge asset as you transform or map it for use in new applications.
Speech Coding for Wireless Communications
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
As one reads this chapter, two trends are evident in the new standards receiving attention today. There is a desire for the capability to code narrowband speech to fullband music inputs, and the end result is more complexity and increasing latency. The LTE and the Opus Codec attempt to satisfy the former while avoiding the increased complexity and latency. It will be interesting to track their success.
A SILK Adaptive Steganographic Scheme Based on Minimizing Distortion in Pitch Domain
Published in IETE Technical Review, 2021
Yanzhen Ren, Shan Zhong, Weiping Tu, Hanyi Yang, Lina Wang
Steganography is a technique that hides secret message in digital carriers for covert communication without arousing any suspicion [1]. As a countermeasure of steganography, steganalysis aims to detect the existence of secret message in those carriers [2]. With the popularity of VOIP and instant voice chat in social application, SILK-compressed audio is widely used in Internet voice communication, such as Skype, WeChat, and Steam game platform. SILK speech codec [3] was first developed by Skype Limited and then incorporated into the Internet Engineering Task Force (IETF) as part of Opus codec, which is the standard of a new Internet wideband audio codec. The codec technology is based on Code Excited Linear Prediction (CELP) framework, combined with the coding principle of iLBC and Speex codec. It is an adaptive coding technology with high coding efficiency in low-rate network environment.