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QCP
The QCP file format is used by many cellular telephone manufacturers to provide ring tones and record voice. It is based on RIFF, a generic format for storing chunks of data identified by tags. The QCP format does not specify how voice data in the file is encoded. Rather, it is a container format. QCP files are typically encoded QCELP or EVRC. Qualcomm, which originated the format, has removed an internal web page link from the page that formerly discussed QCP. "Out of an abundance of caution, due to the December 31st, 2007 injunction ordered against certain Qualcomm products, Qualcomm has temporarily removed certain web content until it can be reviewed and modified if necessary to ensure compliance with the injunction. It may be several more days or weeks before these pages are accessible again. Thank you for your patience." QCP files have the same signature A signature (; from la, signare, "to sign") is a Handwriting, handwritten (and often Stylization, stylized) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ring Tones
A ringtone, ring tone or ring is the sound made by a telephone to indicate an incoming call. Originally referring to and made by the electromechanical striking of bells, the term now refers to any sound on any device alerting of a new incoming call—up to and including recordings of original telephone bells. Electronic telephones, especially smartphones, are manufactured with a preloaded selection of ringtones. Customers can buy or generate custom ringtones for installation on the device. Background and history A telephone rings when the telephone network indicates an incoming call, so that the recipient is alerted of the call attempt. Landline telephones typically receive an electric alternating current signal, called ''power ringing'' or ''ringing signal'', generated by the telephone exchange to which the telephone is connected. The ringing current originally operated an electric bell. For mobile phones, the network sends a message to the recipient's device, which may activa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet Engineering Task Force
The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and all its participants are volunteers. Their work is usually funded by employers or other sponsors. The IETF was initially supported by the federal government of the United States but since 1993 has operated under the auspices of the Internet Society, an international non-profit organization. Organization The IETF is organized into a large number of working groups and birds of a feather informal discussion groups, each dealing with a specific topic. The IETF operates in a bottom-up task creation mode, largely driven by these working groups. Each working group has an appointed chairperson (or sometimes several co-chairs); a charter that describes its focus; and what it is expected to produce, and when. It is open to all who want to pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Qualcomm
Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, 4G, CDMA2000, TD-SCDMA and WCDMA mobile communications standards. Qualcomm was established in 1985 by Irwin M. Jacobs and six other co-founders. Its early research into CDMA wireless cell phone technology was funded by selling a two-way mobile digital satellite communications system known as Omnitracs. After a heated debate in the wireless industry, the 2G standard was adopted with Qualcomm's CDMA patents incorporated. Afterwards there was a series of legal disputes about pricing for licensing patents required by the standard. Over the years, Qualcomm has expanded into selling semiconductor products in a predominantly fabless manufacturing model. It also developed semiconductor components or software for vehicles, watches, laptops, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio File Format
An audio file format is a file format for storing digital audio data on a computer system. The bit layout of the audio data (excluding metadata) is called the audio coding format and can be uncompressed, or compressed to reduce the file size, often using lossy compression. The data can be a raw bitstream in an audio coding format, but it is usually embedded in a container format or an audio data format with defined storage layer. Format types It is important to distinguish between the audio coding format, the container containing the raw audio data, and an audio codec. A codec performs the encoding and decoding of the raw audio data while this encoded data is (usually) stored in a container file. Although most audio file formats support only one type of audio coding data (created with an audio coder), a multimedia container format (as Matroska or AVI) may support multiple types of audio and video data. There are three major groups of audio file formats: * Uncompressed audio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
QCELP
Qualcomm code-excited linear prediction (QCELP), also known as Qualcomm PureVoice, is a speech codec developed in 1994 by Qualcomm to increase the speech quality of the IS-96A codec earlier used in CDMA networks. It was later replaced with EVRC since it provides better speech quality with fewer bits. The two versions, ''QCELP8'' and ''QCELP13'', operate at 8 and 13 kilobits per second (Kbit/s) respectively. In CDMA systems, a QCELP vocoder A vocoder (, a portmanteau of ''voice'' and ''encoder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder ... converts a sound signal into a signal transmissible within a circuit. In wired systems, voice signals are generally sampled at 8 kHz (that is, 8,000 sample values per second) and then encoded by 8-bit quantization for each sample value. Such a system transmits at 64 kbit/s, an expensive ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enhanced Variable Rate Codec
Enhanced Variable Rate CODEC (EVRC) is a speech codec used in CDMA networks. It was developed in 1995 to replace the QCELP vocoder which used more bandwidth on the carrier's network, thus EVRC's primary goal was to offer the mobile carriers more capacity on their networks while not increasing the amount of bandwidth or wireless spectrum needed. EVRC uses RCELP technology. EVRC compresses each 20 milliseconds of 8000 Hz, 16-bit sampled speech input into output frames of one of three different sizes: full rate – 171 bits (8.55 kbit/s), half rate – 80 bits (4.0 kbit/s), eighth rate – 16 bits (0.8 kbit/s). A quarter rate was not included in the original EVRC specification and eventually became part of EVRC-B. EVRC was replaced by SMV. Recently, however, SMV itself has been replaced by the new CDMA2000 4GV codecs. 4GV is the next generation 3GPP2 standards-based EVRC-B codec. 4GV is designed to allow service providers to dynamically prioritize voice capacity on their ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selectable Mode Vocoder
Selectable Mode Vocoder (SMV) is variable bitrate speech coding standard used in CDMA2000 networks. 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. The full rate and half rate are based on the CELP algorithm 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. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Interchange File Format
The Resource Interchange File Format (RIFF) is a generic file container format for storing data in tagged chunks. It is primarily used to store multimedia such as sound and video, though it may also be used to store any arbitrary data. The Microsoft implementation is mostly known through container formats like AVI, ANI and WAV, which use RIFF as their basis. History RIFF was introduced in 1991 by Microsoft and IBM, and was presented by Microsoft as the default format for Windows 3.1 multimedia files. It is based on Electronic Arts' Interchange File Format, introduced in 1985 on the Commodore Amiga, the only difference being that multi-byte integers are in little-endian format, native to the 80x86 processor series used in IBM PCs, rather than the big-endian format native to the 68k processor series used in Amiga and Apple Macintosh computers, where IFF files were heavily used. A RIFX format, which is big-endian, was also introduced. In 2010 Google introduced the WebP pic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Container Format (digital)
A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Notable examples of container formats include archive files (such as the ZIP format) and formats used for multimedia playback (such as Matroska, MP4, and AVI). Among the earliest cross-platform container formats were Distinguished Encoding Rules and the 1985 Interchange File Format. Design Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate codec to decode its contents. If the program doesn't have the required algorithm, it can't use the contained data. In these cases, programs usually emit an error message that complains of a missing codec, which users may be able to acquire. Conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Qualcomm Code-excited Linear Prediction
Qualcomm code-excited linear prediction (QCELP), also known as Qualcomm PureVoice, is a speech codec developed in 1994 by Qualcomm to increase the speech quality of the IS-96A codec earlier used in CDMA networks. It was later replaced with EVRC since it provides better speech quality with fewer bits. The two versions, ''QCELP8'' and ''QCELP13'', operate at 8 and 13 kilobits per second (Kbit/s) respectively. In CDMA systems, a QCELP vocoder A vocoder (, a portmanteau of ''voice'' and ''encoder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder ... converts a sound signal into a signal transmissible within a circuit. In wired systems, voice signals are generally sampled at 8 kHz (that is, 8,000 sample values per second) and then encoded by 8-bit quantization for each sample value. Such a system transmits at 64 kbit/s, an expensive ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magic Number (programming)
In computer programming, a magic number is any of the following: * A unique value with unexplained meaning or multiple occurrences which could (preferably) be replaced with a named constant * A constant numerical or text value used to identify a file format or protocol; for files, see List of file signatures * A distinctive unique value that is unlikely to be mistaken for other meanings (e.g., Globally Unique Identifiers) Unnamed numerical constants The term ''magic number'' or ''magic constant'' refers to the anti-pattern of using numbers directly in source code. This has been referred to as breaking one of the oldest rules of programming, dating back to the COBOL, FORTRAN and PL/1 manuals of the 1960s. The use of unnamed magic numbers in code obscures the developers' intent in choosing that number, increases opportunities for subtle errors (e.g. is every digit correct in 3.14159265358979323846 and is this equal to 3.14159?) and makes it more difficult for the program to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Audio
Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samples are taken 44,100 times per second, each with 16-bit sample depth. Digital audio is also the name for the entire technology of sound recording and reproduction using audio signals that have been encoded in digital form. Following significant advances in digital audio technology during the 1970s and 1980s, it gradually replaced analog audio technology in many areas of audio engineering, record production and telecommunications in the 1990s and 2000s In a digital audio system, an analog electrical signal representing the sound is converted with an analog-to-digital converter (ADC) into a digital signal, typically using pulse-code modulation (PCM). This digital signal can then be recorded, edited, modified, and copied using computers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
