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LPCM
Pulse-code modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Alec Reeves, Claude Shannon, Barney Oliver and John R. Pierce are credited with its invention. Linear pulse-code modulation (LPCM) is a specific type of PCM in which the quantization levels are linearly uniform. This is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm). Though ''PCM'' is a more general term, it is often used to describe data encoded as LPCM. A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the sampling rate, which is the numb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Book (audio CD Standard)
Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standard format for audio compact discs. The standard is defined in the '' Red Book'' technical specifications, which is why the format is also dubbed ''"Redbook audio"'' in some contexts. CDDA utilizes pulse-code modulation (PCM) and uses a 44,100 Hz sampling frequency and 16-bit resolution, and was originally specified to store up to 74 minutes of stereo audio per disc. The first commercially available audio CD player, the Sony CDP-101, was released in October 1982 in Japan. The format gained worldwide acceptance in 1983–84, selling more than a million CD players in its first two years, to play 22.5 million discs, before overtaking records and cassette tapes to become the dominant standard for commercial music. Peaking around year 2000, the audio CD contracted over the next decade due to rising popularity and revenue from digital downloading, and duri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Bit Depth
In digital audio using pulse-code modulation (PCM), bit depth is the number of bits of information in each sample, and it directly corresponds to the resolution of each sample. Examples of bit depth include Compact Disc Digital Audio, which uses 16 bits per sample, and DVD-Audio and Blu-ray Disc, which can support up to 24 bits per sample. In basic implementations, variations in bit depth primarily affect the noise level from quantization error—thus the signal-to-noise ratio (SNR) and dynamic range. However, techniques such as dithering, noise shaping, and oversampling can mitigate these effects without changing the bit depth. Bit depth also affects bit rate and file size. Bit depth is useful for describing PCM digital signals. Non-PCM formats, such as those using lossy compression, do not have associated bit depths. Binary representation A PCM signal is a sequence of digital audio samples containing the data providing the necessary information to reconst ... [...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 audio compression (data), 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 format (digital), container containing the Raw audio format, 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 codec, audio coder), a multimedia container format (as Matroska or Audio Video Interleave, AVI) may support multiple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sampling Rate
In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or space; this definition differs from the term's usage in statistics, which refers to a set of such values. A sampler is a subsystem or operation that extracts samples from a continuous signal. A theoretical ideal sampler produces samples equivalent to the instantaneous value of the continuous signal at the desired points. The original signal can be reconstructed from a sequence of samples, up to the Nyquist limit, by passing the sequence of samples through a reconstruction filter. Theory Functions of space, time, or any other dimension can be sampled, and similarly in two or more dimensions. For functions that vary with time, let s(t) be a continuous function (or "signal") to be sampled, and let sampling be performed by measuring t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sampling (signal Processing)
In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or space; this definition differs from the term's usage in statistics, which refers to a set of such values. A sampler is a subsystem or operation that extracts samples from a continuous signal. A theoretical ideal sampler produces samples equivalent to the instantaneous value of the continuous signal at the desired points. The original signal can be reconstructed from a sequence of samples, up to the Nyquist limit, by passing the sequence of samples through a reconstruction filter. Theory Functions of space, time, or any other dimension can be sampled, and similarly in two or more dimensions. For functions that vary with time, let s(t) be a continuous function (or "signal") to be sampled, and let sampling be performed by measuring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
M2TS
.m2ts is a filename extension used for the Blu-ray disc Audio-Video (BDAV) MPEG-2 Transport Stream (M2TS) container file format. It is used for multiplexing audio, video and other streams, such as subtitles. It is based on the MPEG-2 transport stream container.Blu-ray Disc Association (March 2005BD ROM – Audio Visual Application Format Specifications(PDF) Page 15, Retrieved on 2009-07-26Archived2009-07-29.AfterDawn.coGlossary – BD-MV (Blu-ray Disc Movie) and BDAV container Retrieved on 2009-07-26Archived2009-07-29.AfterDawn.coGlossary – BDAV container Retrieved on 2009-07-26 This container format is commonly used for high-definition video on Blu-ray Disc and AVCHD. Overview The BDAV container format is a modification of the MPEG-2 transport stream (ITU-T H.222.0 , ISO/ IEC 13818-1) specification for random-access media, such as Blu-ray discs, DVDs, hard drives or solid-state memory cards. The format is informally called ''M2TS''. In order to optimize the storage size ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commutator (electric)
A commutator is a rotary switch, electrical switch in certain types of electric motors and electrical generators that periodically reverses the Current (electricity), current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature (electrical engineering), armature of the machine. Two or more electrical contacts called "brush (electric), brushes" made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the armature (electrical engineering), armature are connected to the commutator segments. Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors. In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating windings each half turn, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moses G
In Abrahamic religions, Moses was the Hebrew prophet who led the Israelites out of slavery in the Exodus from Egypt. He is considered the most important prophet in Judaism and Samaritanism, and one of the most important prophets in Christianity, Islam, the Baháʼí Faith, and Table of prophets of Abrahamic religions, other Abrahamic religions. According to both the Bible and the Quran, God in Abrahamic religions, God dictated the Mosaic Law to Moses, which he Mosaic authorship, wrote down in the five books of the Torah. According to the Book of Exodus, Moses was born in a period when his people, the Israelites, who were an slavery, enslaved minority, were increasing in population; consequently, the Pharaohs in the Bible#In the Book of Exodus, Egyptian Pharaoh was worried that they might ally themselves with New Kingdom of Egypt, Egypt's enemies. When Pharaoh ordered all newborn Hebrew boys to be killed in order to reduce the population of the Israelites, Moses' Hebrew mother ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telegraphy
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pigeon post is not. Ancient signalling systems, although sometimes quite extensive and sophisticated as in China, were generally not capable of transmitting arbitrary text messages. Possible messages were fixed and predetermined, so such systems are thus not true telegraphs. The earliest true telegraph put into widespread use was the Chappe telegraph, an optical telegraph invented by Claude Chappe in the late 18th century. The system was used extensively in France, and European nations occupied by France, during the Napoleonic era. The electric telegraph started to replace the optical telegraph in the mid-19th century. It was first taken up in Britain in the form of the Cooke and Wheatstone telegraph, initially used mostly as an aid to railw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barney Oliver
Bernard More Oliver (May 17, 1916 – November 23, 1995) also known as Barney Oliver, was an American engineer who made contributions in many fields, including radar, television, and computers. He was the founder and director of Hewlett-Packard (HP) laboratories until his retirement in 1981. He is also a recognized pioneer in the search for extraterrestrial intelligence (SETI). Oliver was president of the Institute of Electrical and Electronics Engineers in 1965. In 1973, Oliver was elected to the National Academy of Sciences. In 1986, Oliver received the National Medal of Science for Engineering Science. In 2004, Oliver was inducted into the National Inventors Hall of Fame. The asteroid, 2177 Oliver, is named after him. Early life and education Bernard (Barney) More Oliver, born to Margaret (née More) and William Oliver, was a native of Santa Cruz, California, grew up on a ranch in the Soquel Valley, and at age 19, received an undergraduate degree from Stanford in 1935. He t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephony
Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is intimately linked to the invention and development of the telephone. Telephony is commonly referred to as the construction or operation of telephones and telephonic systems and as a system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires. The term is also used frequently to refer to computer hardware, software, and computer network systems, that perform functions traditionally performed by telephone equipment. In this context the technology is specifically referred to as Internet telephony, or voice over Internet Protocol (VoIP). Overview The first telephones were connected directly in pairs: each user had a separate telephone wire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
