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| Filename extension | .spx |
|---|---|
| Internet media type | audio/x-speex, audio/speex, audio/ogg |
| Developed by | Xiph.Org Foundation, Jean-Marc Valin |
| Type of format | Audio |
| Contained by | Ogg |
| Standard(s) | RFC 5574 |
| Website | www.speex.org |
| Developer(s) | Xiph.Org Foundation, Jean-Marc Valin[1] |
|---|---|
| Initial release | 1.0 / March 2003 |
| Stable release | 1.1.12[2] / February 19, 2006 |
| Preview release | 1.2rc1 / July 23, 2008 |
| Operating system | Cross-platform |
| Type | Audio codec, reference implementation |
| License | BSD-style license[3][4] |
| Website | Xiph.org downloads |
Speex is a patent-free audio compression format designed for speech and also a free software speech codec that may be used on VoIP applications and podcasts.[5] It is based on the CELP speech coding algorithm.[6] 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.
The Speex designers see their project as complementary to the Vorbis general-purpose audio compression project.
Speex is a lossy format, meaning quality is permanently degraded to reduce file size.
The Speex project was created on February 13, 2002.[7] The first development versions of Speex were released under LGPL license, but as of version 1.0 beta 1, Speex is released under Xiph's version of the (revised) BSD license.[8] Speex 1.0 was announced on March 24, 2003, after a year of development.[9] The last stable version of Speex encoder and decoder is 1.1.12.[2]
Contents |
Description [link]
Unlike many other speech codecs, Speex is not targeted at cellular telephony 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). Since Speex was designed for Voice over IP (VoIP) instead of cell phone use, the codec must be robust to lost packets, but not to corrupted ones. All this led to the choice of Code Excited Linear Prediction (CELP) as the encoding technique to use for Speex.[6] 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:
- 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) (not working from version 1.2).
- Variable complexity.
- Ultra-wideband mode at 32 kHz (up to 48 kHz).
- Intensity stereo encoding option.
Features [link]
- 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 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,[10] though higher settings are often useful when encoding non-speech sounds like DTMF tones, or if encoding is not in real-time.
- 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 three main drawbacks: first, by only specifying quality, there is 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. Third, encryption of VBR-encoded speech may not ensure complete privacy, as phrases can still be identified, at least in a controlled setting with a small dictionary of phrases,[11] by analysing the pattern of variation of the bit rate.
- 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). Last version VAD was working fine is 1.1.12, since v 1.2 it has been replaced with simple Any Activity Detection.
- 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 a file, 5 bits are used for each missing frame (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.
Applications [link]
There is already a large base of applications supporting the Speex codec, from streaming applications like teleconference (e.g. TeamSpeak; many servers prefer Speex due to its good quality), to VoIP systems (e.g. Asterisk), to videogames (e.g. Xbox Live,[12] Civilization 4) and audio processing applications. Most of these are based on the DirectShow filter or OpenACM codec (e.g. Microsoft NetMeeting) on Microsoft Windows, or Xiph.org's reference implementation, libvorbis, on Linux (e.g. Ekiga). There are also plugins for many audio players. See the plugin and software page on the speex.org site for more details.
The media type for Speex is audio/ogg while contained by Ogg, and audio/speex (previously audio/x-speex) when transported through RTP or without container.
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 Ear Bible is a single-ear headphone with a built-in Speex player with 1 GB of flash memory[13], preloaded with a recording of the New American Standard Bible.
ASL Safety & Security's Linux based VIPA OS software[14] which is used in long line public address systems and voice alarm systems at major international air transport hubs and rail networks.
The Rockbox project uses Speex for its voice interface. It can also play Speex files on supported players, such as the Apple iPod or the iRiver H10.
The Vernier LabQuest handheld data acquisition device for science education uses Speex for voice annotations created by students and teachers using either the built-in or an external microphone.
The Google Mobile App for iPhone currently incorporates Speex.[15] It has also been suggested that the new Google voice search iPhone app is using Speex to transmit voice to Google servers for interpretation.[16]
Adobe Flash Player supports Speex starting with Flash Player 10.0.12.36, released in October 2008.[17] Because of some bugs in Flash Player, the first recommended version for Speex support is 10.0.22.87 and later. Speex in Flash Player can be used for both kind of communication, through Flash Media Server or P2P. Speex can be decoded or converted to any format unlike Nellymoser audio, which was the only speech format in previous versions of Flash Player.[18][19] Speex can be also used in the Flash Video container format (.flv), starting with version 10 of Video File Format Specification (published in November 2008).[20]
The JavaSonics ListenUp voice recorder uses Speex to compress voice messages that are recorded in a browser and then uploaded to a web server. Primary applications are language training, transcription and social networking.
Speex is used as the voice compression algorithm in the Siri voice assistance on the iPhone 4S.[21] Since text-to-speech occurs on Apple's servers, the Speex codec is used to minimize network bandwidth.
See also [link]
References [link]
- ^ "people.xiph.org - personal webspace of the xiphs - Jean-Marc Valin". Xiph.Org. 2009. https://people.xiph.org/~jm/. Retrieved 2009-09-11.
- ^ a b "Speex News". Xiph.Org Foundation. https://www.speex.org/news/. Retrieved 2009-09-01.
- ^ "The Speex Codec Manual - Speex License". Xiph.Org Foundation. https://www.speex.org/docs/manual/speex-manual/node15.html. Retrieved 2009-09-01.
- ^ "Sample Xiph.Org Variant of the BSD License". Xiph.Org Foundation. https://www.xiph.org/licenses/bsd/. Retrieved 2009-08-29.
- ^ Xiph.Org Speex: A Free Codec For Free Speech, Retrieved 2009-09-01
- ^ a b Xiph.Org Introduction to CELP Coding, Retrieved 2009-09-01
- ^ Xiph.org Speex releases - pre-1.0 - NEWS and ChangeLog in speex-0.0.1.tar.gz, Retrieved 2009-09-01
- ^ Xiph.Org Speex FAQ - Under what license is Speex released?, Retrieved 2009-09-01
- ^ Xiph.Org (2003-03-24) Speex reaches 1.0; Xiph.Org now a 501(c)(3) Non-Profit Organization, Retrieved 2009-09-01
- ^ Codec Description
- ^ https://www.cs.jhu.edu/~fabian/papers/oakland08.pdf Spot me if you can: Uncovering Spoken Phrases in Encrypted VoIP Conversations (Charles V. Wright Lucas Ballard Scott E. Coull Fabian Monrose Gerald M. Masson)
- ^ As announced by Ralph Giles, the Theora codec maintainer, on LugRadio episode 29
- ^ [1]
- ^ IPAM 400: IP Based Intelligent Public Address Amplifier - User Manual
- ^ https://m.google.com/static/legalnotices.html
- ^ Deconstructing Google Mobile's Voice Search on the iPhone
- ^ Adobe (2008) Flash Player 10 Datasheet, Retrieved 2009-09-01
- ^ AskMeFlash.com (2009-05-10) Speex for Flash, Retrieved on 2009-08-12
- ^ AskMeFlash.com (2009-05-10) Speex vs Nellymoser, Retrieved on 2009-08-12
- ^ Adobe Systems Incorporated (November 2008) (PDF). Video File Format Specification, Version 10. Adobe Systems Incorporated. https://www.adobe.com/devnet/flv/pdf/video_file_format_spec_v10.pdf. Retrieved 2009-09-01.[dead link]
- ^ [2]
External links [link]
- RFC 5574 - RTP Payload Format for the Speex Codec
- Official Speex homepage
- Plugin & software page
- JSpeex is a port of Speex to the Java platform
- NSpeex is a port of Speex to the .NET platform and Silverlight based on JSpeex
- CSpeex is a port of Speex to the .NET platform based on JSpeex
- Speex for flash
- RFC 5334 - Ogg Media Types
This article uses material from the Speex Codec Manual which is copyright © Jean-Marc Valin and licensed under the terms of the GFDL.
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https://wn.com/Speex
SPX
SPX can refer to:
SpaceX CRS-6
SpaceX CRS-6, also known as SpX-6, was a cargo resupply mission to the International Space Station, contracted to NASA. It was the eighth flight for SpaceX's uncrewed Dragon cargo spacecraft and the sixth SpaceX operational mission contracted to NASA under a Commercial Resupply Services contract. It was docked to the International Space Station from 17 April to 21 May 2015.
Launch history
As of July 2014, the launch was tentatively scheduled by NASA for February 2015, with berthing to the station occurring two days later. However, as a result of delays in the launch of the previous SpaceX CRS-5 mission, CRS-6 launched on April 14, 2015. In late March 2015, the launch was tentatively scheduled for April 13, 2015, but was later postponed to April 14, 2015 due to weather conditions.
A Federal Communications Commission application submitted for temporary communication frequency authority notes the launch planning date as no earlier than April 8, 2015. The application also confirms communication uplinks for use with the first stage of this mission as it conducts another attempt at a first-ever propulsive landing on the Autonomous spaceport drone ship after staging.
Therapy
Therapy (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a diagnosis. In the medical field, it is usually synonymous with treatment (also abbreviated tx or Tx), which is used more commonly than "therapy". Among psychologists and other mental health professionals, including psychiatrists, psychiatric nurse practitioners, and clinical social workers, the term may refer specifically to psychotherapy (sometimes dubbed 'talking therapy'). The English word therapy comes via Latin therapīa from Greek: θεραπεία and literally means "curing" or "healing".
As a rule, each therapy has indications and contraindications.
Semantic field
Therapy?
Therapy? is an alternative metal band from Northern Ireland. The band was formed in 1989 by guitarist–vocalist Andy Cairns from Ballyclare and drummer-vocalist Fyfe Ewing from Larne, Northern Ireland. The band initially recorded their first demo with Cairns filling in on bass guitar. To complete the lineup, the band recruited Larne bassist Michael McKeegan.
With keen pop sensibilities, a skewed sense of humour and a willingness to draw inspiration from diverse sources (notably punk rock), Therapy? came to attention in the early 1990s rise of alternative rock, but have endured for two decades since; critic Johnny Loftus writes:
"after a ten-plus year career that has seen them outlast competitors and outwit industry attempts at categorization... Therapy are still headbangers with their thinking caps screwed on tight."
Following the addition of Neil Cooper on drums, the band has enjoyed a stable lineup since 2004. Therapy? are currently signed to new UK independent label Amazing Record Co.. The band has sold over two million albums worldwide.
Therapy (Lodge novel)
Therapy (1995) is a novel by British author David Lodge.
The story concerns a successful sitcom writer, Laurence Passmore, plagued by middle-age neuroses and a failed marriage. His only problem seems to be an "internal derangement of the knee" but a mid-life crisis has struck and he is discovering angst. His familiar doses of cognitive therapy, aromatherapy, and acupuncture all offer no help, and he becomes obsessed with the philosophy of Kierkegaard. Moreover, Tubby, as Passmore is nicknamed, and referred to by several characters in the novel, undertakes a pilgrimage to Santiago de Compostela in order to find his first love.
Structure of the novel
The novel is divided into four parts. The first part is written as a journal, the second part is written in dramatic monologues, the third part consists of journal entries and a memoir and the fourth part is a narrative written after the events happened and Tubby has returned to London.
In the first part, Tubby starts writing a journal triggered by a description he had to write for his cognitive behavior therapist. Before that Tubby wrote only screenplays but no narrative texts. During the writing Tubby reflects upon his problems and depression.
