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Selectable Mode Vocoder (SMV) is variable bitrate speech coding standard used in CDMA2000 networks[1]. SMV provides multiple modes of operation that are selected based on input speech characteristics.
The SMV for Wideband CDMA is based on 4 codecs: full rate at 8.5 kbit/s, half rate at 4 kbit/s, quarter rate at 2 kbit/s, and eighth rate at 800 bit/s.[1] The full rate and half rate are based on the CELP algorithm[1] that is based on a combined closed-loop-open-loop-analysis (COLA). In SMV the signal frames are first classified as:
- Silence/Background noise
- Non-stationary unvoiced
- Stationary unvoiced
- Onset
- Non-stationary voiced
- Stationary voiced
The algorithm includes voice activity detection (VAD) followed by an elaborate frame classification scheme. Silence/background noise and stationary unvoiced frames are represented by spectrum-modulated noise and coded at 1/4 or 1/8 rate. The SMV uses 4 subframes for full rate and two/three subframes for half rate. The stochastic (fixed) codebook structure is also elaborate and uses sub-codebooks each tuned for a particular type of speech. The sub-codebooks have different degrees of pulse sparseness (more sparse for noise like excitation). SMV scores a high of 3.6 MOS[2] at full rate with clean speech.
The coder works on a frame of 160 speech samples (20 ms) and requires a look ahead of 80 samples (10 ms) if noise-suppression option B is used. An additional 24 samples of look ahead is required if noise-suppression option A is used. So the algorithmic delay for the coder is 30 ms with noise-suppression option B and 33 ms with noise-suppression option A.
The next evolution of CDMA speech codecs is VMR-WB which provides much higher speech quality with wideband while fitting to the same networks.
SMV can be also used in 3GPP2 container file format - 3G2.
References [link]
- ^ a b c "3GPP2 C.S0030-0 Selectable Mode Vocoder (SMV) Service Option for Wideband Spread Spectrum Communication Systems" (PDF). 3rd Generation Partnership Project 2. 2004. https://www.3gpp2.org/public_html/specs/C.S0030-0_v3.0_040325.pdf. Retrieved 2009-05-26.
- ^ J. Makinen, P. Ojala, H. Toukomaa. "Performance Comparison of Source Controlled GSM AMR and SMV Vocoders" (PDF). Nokia Research Center, Multimedia Technologies Laboratory. https://europe.nokia.com/library/files/docs/Makinen2.pdf. Retrieved 2009-05-26.
External links [link]
- RFC 3558 - RTP Payload Format for Enhanced Variable Rate Codecs (EVRC) and Selectable Mode Vocoders (SMV)
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https://wn.com/Selectable_Mode_Vocoder
Thunder
Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave, similar to a sonic boom, which produces the sound of thunder, often referred to as a clap, crack, or peal of thunder.
Cause
The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the fourth century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories were proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum.
In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. The temperature inside the lightning channel, measured by spectral analysis, varies during its 50 μs existence, rising sharply from an initial temperature of about 20,000 K to about 30,000 K, then dropping away gradually to about 10,000 K. The average is about 20,400 K (20,100 °C; 36,300 °F). This heating causes a rapid outward expansion, impacting the surrounding cooler air at a speed faster than sound would otherwise travel. The resultant outward-moving pulse is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft.
Thunder (Andy Taylor album)
Thunder is the first solo album by British guitarist Andy Taylor, released in 1987. It features former Sex Pistols guitarist Steve Jones on guitar. Jones also co-wrote most of the songs on the album.
The album went out of print in 1990, but would reemerge in a newly expanded version on online music services like iTunes when Taylor made his entire catalog available in 2010. In addition to the original version of Thunder, Taylor's previous solo singles such as "Take It Easy" were included as well.
Track listing
Personnel
Thunder (ship)
FV Thunder was an outlaw fishing vessel sunk in 2015. The ship was built in 1969 in Norway and has gone by many names, including: Vesturvón, Arctic Ranger, Rubin, Typhoon I, Kuko, and Wuhan N4. The ship was last registered in Lagos, Nigeria; however, the ship was officially de-listed by Nigeria a week before it sank.
At the time of its sinking, the crew consisted of 30 Indonesians and 10 officers from Spain, Chile, and Portugal, who were turned over to the authorities in São Tomé and Príncipe. The officers of the crew were later tried and convicted of several illegal fishing offences. The captain, Luis Alfonso Rubio Cataldo of Chile, was given a three year sentence. The ship's chief engineer, Agustín Dosil Rey of Spain, was given a two year and nine month sentence. The ship's second mechanic, Luis Miguel Pérez Fernández of Spain, was given a two year and eight month sentence. Together, they were fined a total of over $17 million.Interpol believes that the vessel was part of a fleet of six operating through shell corporations under Vidal Armadores, a company based in Spain.
