Speex is a free software speech codec that may be used on VoIP applications and podcasts. Speex claims to be free of any patent restrictions and is licensed under the revised (3-clause) BSD license. It may be used with the Ogg container format or directly transmitted over UDP/RTP. A filename extension is a suffix to the name of a computer file applied to show its format. ... An audio codec is a computer program that compresses/decompresses digital audio data according to a given audio file format or streaming audio format. ... Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ... Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ... Clockwise from top: The logo of the GNU Project (the GNU head), the Linux kernel mascot Tux the Penguin, and the FreeBSD daemon Free software is a term coined by Richard Stallman and the Free Software Foundation[1] to refer to software that can be used, studied, and modified without... Speech coding is the compression of speech (into a code) for transmission with speech codecs that use audio signal processing and speech processing techniques. ... An overview of how VoIP works A typical analog telephone adapter for connecting an ordinary phone to a VoIP network Ciscos implementation of VoIP - IP Phone Voice over Internet Protocol, also called VoIP, IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the routing of... An orange square with waves indicates that an RSS feed is present on a web page. ... Software patent does not have a universally accepted definition. ... The BSD license is a permissive license and is one of the most widely used free software licenses. ... Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ... A container format is a computer file format that can contain various types of data, compressed by means of standardized codecs. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... The Real-time Transport Protocol (or RTP) defines a standardized packet format for delivering audio and video over the Internet. ...

The Speex designers see their project as complementary to the Vorbis general-purpose audio compression project. Vorbis is an open source, lossy audio codec project headed by the Xiph. ... Audio compression can mean two things: Audio data compression - in which the amount of data in a recorded waveform is reduced for transmission. ...

Speex is a lossy format, meaning quality is permanently degraded to reduce file size. A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. ...

Description

Unlike many other speech codecs, Speex is not targeted at cell phones but rather at Voice over IP (VoIP) and file-based compression. The design goals have been to make a codec that would be optimized for high quality speech and low bit rate. To achieve this the codec uses multiple bit rates, and supports ultra-wideband (32 kHz sampling rate), wideband (16 kHz sampling rate) and narrowband (telephone quality, 8 kHz sampling rate). Designing for Voice over IP (VoIP) instead of cell phone use means that Speex must be robust to lost packets, but not to corrupted ones since the User Datagram Protocol (UDP) ensures that packets either arrive unaltered or don't arrive. All this led to the choice of Code Excited Linear Prediction (CELP) as the encoding technique to use for Speex. One of the main reasons is that CELP has long proven that it could do the job and scale well to both low bit rates (as evidenced by DoD CELP @ 4.8 kbit/s) and high bit rates (as with G.728 @ 16 kbit/s). The main characteristics can be summarized as follows: An overview of how VoIP works A typical analog telephone adapter for connecting an ordinary phone to a VoIP network Ciscos implementation of VoIP - IP Phone Voice over Internet Protocol, also called VoIP, IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the routing of... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ... Wideband is a relative term used to describe a wide range of frequencies in a spectrum. ... IP Telephony, also called Internet telephony, is the technology that makes it possible to have a telephone conversation over the Internet or a dedicated Internet Protocol (IP) network instead of dedicated voice transmission lines. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... CELP stands for Code Excited Linear Prediction and is a speech coding algorithm originally proposed by M.R. Schroeder and B.S. Atal in 1984. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... G.728 is a ITU-T standard for speech coding operating at 16 kbit/s. ...

• Free software/open-source, patent and royalty-free
• Integration of narrowband and wideband in the same bit-stream
• Wide range of bit rates available (from 2 kbit/s to 44 kbit/s)
• Dynamic bit rate switching and Variable bit-rate (VBR)
• Voice Activity Detection (VAD, integrated with VBR)
• Variable complexity
• Ultra-wideband mode at 32 kHz (up to 48 kHz)
• Intensity stereo encoding option

Clockwise from top: The logo of the GNU Project (the GNU head), the Linux kernel mascot Tux the Penguin, and the FreeBSD daemon Free software is a term coined by Richard Stallman and the Free Software Foundation[1] to refer to software that can be used, studied, and modified without... For other uses, see Patent (disambiguation). ... This article or section does not adequately cite its references or sources. ... Variable bit rate (VBR) is a term used in telecommunications, relating to the quality of service. ... Intensity stereo is a term that refers to a stereo sound image that is produced only by the difference in volume of something in the loudspeakers, as opposed to time arrival differences - see Haas Effect. ...

Features

Sampling rate

Speex is mainly designed for three different sampling rates: 8 kHz (the same sampling rate to transmit telephone calls), 16 kHz, and 32 kHz. These are respectively referred to as narrowband, wideband and ultra-wideband.

Quality

Speex encoding is controlled most of the time by a quality parameter that ranges from 0 to 10. In constant bit-rate (CBR) operation, the quality parameter is an integer, while for variable bit-rate (VBR), the parameter is a real (floating point) number.

Complexity (variable)

With Speex, it is possible to vary the complexity allowed for the encoder. This is done by controlling how the search is performed with an integer ranging from 1 to 10 in a way that's similar to the -1 to -9 options to gzip compression utilities. For normal use, the noise level at complexity 1 is between 1 and 2 dB higher than at complexity 10, but the CPU requirements for complexity 10 is about five times higher than for complexity 1. In practice, the best trade-off is between complexity 2 and 4^{[citation needed]}, though higher settings are often useful when encoding non-speech sounds like DTMF tones.

Variable Bit-Rate (VBR)

Variable bit-rate (VBR) allows a codec to change its bit rate dynamically to adapt to the "difficulty" of the audio being encoded. In the example of Speex, sounds like vowels and high-energy transients require a higher bit rate to achieve good quality, while fricatives (e.g. s and f sounds) can be coded adequately with fewer bits. For this reason, VBR can achieve lower bit rate for the same quality, or a better quality for a certain bit rate. Despite its advantages, VBR has two main drawbacks: first, by only specifying quality, there's no guarantee about the final average bit-rate. Second, for some real-time applications like voice over IP (VoIP), what counts is the maximum bit-rate, which must be low enough for the communication channel.

Average Bit-Rate (ABR)

Average bit-rate solves one of the problems of VBR, as it dynamically adjusts VBR quality in order to meet a specific target bit-rate. Because the quality/bit-rate is adjusted in real-time (open-loop), the global quality will be slightly lower than that obtained by encoding in VBR with exactly the right quality setting to meet the target average bitrate.

Voice Activity Detection (VAD)

When enabled, voice activity detection detects whether the audio being encoded is speech or silence/background noise. VAD is always implicitly activated when encoding in VBR, so the option is only useful in non-VBR operation. In this case, Speex detects non-speech periods and encodes them with just enough bits to reproduce the background noise. This is called "comfort noise generation" (CNG).

Discontinuous Transmission (DTX)

Discontinuous transmission is an addition to VAD/VBR operation, that allows to stop transmitting completely when the background noise is stationary. In file-based operation, since we cannot just stop writing to the file, only 5 bits are used for such frames (corresponding to 250 bit/s).

Perceptual enhancement

Perceptual enhancement is a part of the decoder which, when turned on, tries to reduce (the perception of) the noise produced by the coding/decoding process. In most cases, perceptual enhancement makes the sound further from the original objectively (signal-to-noise ratio), but in the end it still sounds better (subjective improvement).

Algorithmic delay

Every codec introduces a delay in the transmission. For Speex, this delay is equal to the frame size, plus some amount of "look-ahead" required to process each frame. In narrowband operation (8 kHz), the delay is 30 ms, while for wideband (16 kHz), the delay is 34 ms. These values don't account for the CPU time it takes to encode or decode the frames.

For other uses, see Telephone (disambiguation). ... The integers are commonly denoted by the above symbol. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... The correct title of this article is . ... In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... Dual-tone multi-frequency (DTMF), also known as Touch Tone® is used for telephone signaling over the line in the voice frequency band to the call switching center. ... Note: This page contains IPA phonetic symbols in Unicode. ... Transient means passing with time. ... Note: This page contains phonetic information presented in the International Phonetic Alphabet (IPA) using Unicode. ... An overview of how VoIP works A typical analog telephone adapter for connecting an ordinary phone to a VoIP network Ciscos implementation of VoIP - IP Phone Voice over Internet Protocol, also called VoIP, IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the routing of... Comfort noise is artifical background noise used in radio and wireless communications to fill the silent time in a transmission resulting from voice activity detection. ...

Large application base

There is already a large base of applications supporting the Speex codec, from streaming applications like teleconference to videogames and audio processing applications. Most of these are based on the DirectShow filter, OpenACM codec—Netmeeting on Microsoft Windows, or OpenH323 on Linux (Ekiga), for example. There are also plugins for the Winamp and XMMS players. Also KSP Sound Player from version 2006.0.0.2 and foobar2000 support Speex. Streaming media is multimedia that is continuously received by, and normally displayed to, the end-user while it is being delivered by the provider. ... // Bold textBold textBold textBold textIn telecommunication, teleconference is the live exchange and mass articulation of information among persons and machines remote from one another but linked by a telecommunications system, usually over the phone line. ... Logo of the DirectX Media SDK - the first time DirectShow was distributed under its current name. ... This article or section should be merged with Video teleconference A videoconference is a live connection between people in separate locations for the purpose of communication, usually involving audio and often text as well as video. ... Windows redirects here. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system. ... Ekiga (formerly known as GnomeMeeting) is an open source VoIP and video conferencing application for GNOME. Ekiga uses both the H.323 and SIP protocols. ... A plugin (plug-in, addin, add-in, addon or add-on) is a computer program that interacts with a main (or host) application (a web browser or an email program, for example) to provide a certain, usually very specific, function on demand. ... Winamp is a proprietary media player written by Nullsoft, a subsidiary of Time Warner. ... XMMSs default appearance The X Multimedia System (XMMS) is a free audio player very similar to Winamp, that runs on many Unix-like operating systems. ... KSP (KSP Sound Player or Kalliope Sound Player) is a free audio player for Windows which is developed and distributed by Kalliope s. ... foobar2000 is a freeware audio player for Windows developed by Peter Pawlowski, a former freelance contractor for Nullsoft. ...

The MIME type for Speex is audio/x-speex. The type audio/speex will be applied for in the near future. Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support: text in character sets other than US-ASCII; non-text attachments; multi-part message bodies; and header information in non-ASCII character sets. ...

See the plugin and software page on speex.org site for more details.

Microsoft's Xbox Live uses Speex for the headsets, as announced by Ralph Giles, the Theora codec maintainer, on LugRadio. Xbox Live is a subscription-based online gaming service for Microsofts Xbox and Xbox 360 video game consoles. ... Theora is a video codec being developed by the Xiph. ... LugRadio is a UK-based podcast aimed at fans of Linux and open source software. ...

The latest Half-Life 1 engine and mods use the voice_speex.dll codec as its ingame VoIP function. Though it is not enabled by default, server administrators must enable it by typing in the console of their server either through rcon or at the physical server computer "sv_voicecodec voice_speex". Speex provides much better quality than the default Miles voice codec. Half-Life is a science fiction first-person shooter computer game developed by Valve Software and published by Sierra On-Line in 1998, based on a heavily-modified Quake game engine. ...

The United States Army's Land Warrior system, designed by General Dynamics, also uses Speex for VoIP on an EPLRS radio designed by Raytheon. The United States Army is the largest and oldest branch of the armed forces of the United States. ... Land Warrior is a United States Army program that uses a combination of commercial, off-the-shelf technology (COTS) and current-issue military gear and equipment designed to: Integrate small arms with high-tech equipment Provide communications and command and control at the infantry soldier level Look at the individual... General Dynamics (NYSE: GD) is a defense conglomerate formed by mergers and divestitures, and as of 2005 it is the sixth largest defense contractor in the world[1]. The company has changed markedly in the post-Cold War era of defense consolidation. ... The Enhanced Position Location Reporting System (ELPRS) or AN/TSQ-158 is a secure, jam resistant, computer controlled communications network that distributes near real-time tactical information, generally integrated into radio sets, and coordinated by a Network Control Station. ... Raytheon Company (NYSE: RTN) is a major United States military contractor based in Waltham, Massachusetts. ...

In Sid Meier's Civilization 4, Speex is used to encode the descriptions of the technologies as read by Leonard Nimoy. Civilization IV is a turn-based strategy computer game currently being developed by Sid Meier and his studio Firaxis Games. ... Leonard Simon Nimoy (born March 26, 1931) is an American actor, film director, poet, musician and photographer. ...

The VoIP Program Teamspeak Uses Speex codecs as one of the 3 codecs available. the range of quality starts from 3.4Kbit to 25.9Kbit. Many servers prefer the Speex codec due to its good quality with little or many people in a room. TeamSpeak is proprietary Voice over IP software that allows users to speak on a chat channel with other users, much like a telephone conference call. ...

The Rockbox project can also play of Speex files on support players such as the Apple iPod or the iRiver H10. Rockbox is a free software replacement for the firmware held on various forms of digital audio players (DAPs). ...

See also

Free software Portal

• Comparison of audio codecs

Image File history File links Portal. ... The following tables compare general and technical information for a variety of audio codecs. ...

External links

• Official Speex homepage
• Plugin & software page
• JSpeex is a port of Speex to the Java platform

This article uses material from the Speex Codec Manual which is copyright © Jean-Marc Valin and licensed under the terms of the GFDL