41-475: Supermac may refer to: Precursor technology to AES50 Harold Macmillan (1894–1986), nicknamed "Supermac", Prime Minister of the United Kingdom from 1957 to 1963 Supermac (cartoon) , relating to Harold Macmillan the former British Prime Minister Malcolm "Supermac" Macdonald (born 1950), a retired English football player and pundit Super Mac Race ,
82-416: A voltage or current (depending on type) that represents the value presented on their digital inputs. This output would then generally be filtered and amplified for use. To recover the original signal from the sampled data, a demodulator can apply the procedure of modulation in reverse. After each sampling period, the demodulator reads the next value and transitions the output signal to the new value. As
123-593: A 568 mile sailboat race starting in Lake Michigan off Chicago, IL and ending in Lake Huron off Port Huron, MI. Supermac's , an Irish fast food chain covering Northern Ireland and the Republic of Ireland Supermac Ltd, Belfast, Northern Ireland's first out of town supermarket, opened 1964 and since demolished for Forestside Shopping Centre SuperMac , a brand of Macintosh clones made by UMAX SuperMac Technologies,
164-410: A DS0 is either μ-law (mu-law) PCM (North America and Japan) or A-law PCM (Europe and most of the rest of the world). These are logarithmic compression systems where a 12- or 13-bit linear PCM sample number is mapped into an 8-bit value. This system is described by international standard G.711 . Where circuit costs are high and loss of voice quality is acceptable, it sometimes makes sense to compress
205-482: A NRZ system to be synchronized using in-band information, there must not be long sequences of identical symbols, such as ones or zeroes. For binary PCM systems, the density of 1-symbols is called ones-density . Ones-density is often controlled using precoding techniques such as run-length limited encoding, where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into
246-512: A hardware and software company that developed (amongst other things) the Cinepak codec Detective Chief Superintendent Charlie "SuperMac" Mackintosh, a character in Ashes to Ashes , a 2009 BBC television drama Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Supermac . If an internal link led you here, you may wish to change
287-455: A larger aggregate data stream , generally for transmission of multiple streams over a single physical link. One technique is called time-division multiplexing (TDM) and is widely used, notably in the modern public telephone system. The electronics involved in producing an accurate analog signal from the discrete data are similar to those used for generating the digital signal. These devices are digital-to-analog converters (DACs). They produce
328-547: A result of these transitions, the signal retains a significant amount of high-frequency energy due to imaging effects. To remove these undesirable frequencies, the demodulator passes the signal through a reconstruction filter that suppresses energy outside the expected frequency range (greater than the Nyquist frequency f s / 2 {\displaystyle f_{s}/2} ). Common sample depths for LPCM are 8, 16, 20 or 24 bits per sample . LPCM encodes
369-502: A single sound channel. Support for multichannel audio depends on file format and relies on synchronization of multiple LPCM streams. While two channels (stereo) is the most common format, systems can support up to 8 audio channels (7.1 surround) or more. Common sampling frequencies are 48 kHz as used with DVD format videos, or 44.1 kHz as used in CDs. Sampling frequencies of 96 kHz or 192 kHz can be used on some equipment, but
410-462: A single telegraph cable. The American inventor Moses G. Farmer conceived telegraph time-division multiplexing (TDM) as early as 1853. Electrical engineer W. M. Miner, in 1903, used an electro-mechanical commutator for time-division multiplexing multiple telegraph signals; he also applied this technology to telephony . He obtained intelligible speech from channels sampled at a rate above 3500–4300 Hz; lower rates proved unsatisfactory. In 1920,
451-629: A time. Rather than natural binary, the grid of Goodall's later tube was perforated to produce a glitch-free Gray code and produced all bits simultaneously by using a fan beam instead of a scanning beam. In the United States, the National Inventors Hall of Fame has honored Bernard M. Oliver and Claude Shannon as the inventors of PCM, as described in "Communication System Employing Pulse Code Modulation", U.S. patent 2,801,281 filed in 1946 and 1952, granted in 1956. Another patent by
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#1732859466345492-405: 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
533-459: Is 6 samples at 96 kHz and 3 samples at 48 kHz, or 62.50 μs. In practical implementations of the SuperMAC and HyperMAC protocols, only 96 kHz PCM formats are supported. AES50 also supports packet-based auxiliary channel for control data over the same data link. The control channel is allocated a fixed bandwidth of 5 Mbit/s; control data are embedded in the same Ethernet frame as
574-645: Is defined in the AES50-2011 standard for High-resolution multi-channel audio interconnection (HRMAI) . AES50 is based on the SuperMAC protocol created by Sony Pro Audio Lab (now Oxford Digital ). The preliminary standard was assigned the AES-X140 project designation in 2003, and was finally approved in 2005 as a royalty-free open standard . HyperMAC is an improved protocol based on Gigabit Ethernet physical layer, allowing more channels and lower audio latency . It
615-412: Is implemented in digital mixing consoles by Midas and Behringer to transfer digital audio between a console and remote stage boxes . AES50 is a point-to-point interconnect which carries multiple channels of AES3 , PCM or DSD bitstream formats, along with system clock and synchronisation signals, over Cat 5 cable using 100 Mbit/s Fast Ethernet physical layer. AES50 uses the four pairs of
656-439: Is increased to 200 Mbit/s and control data is transmitted with separate control frames. PCM 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
697-648: 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 number of times per second that samples are taken; and the bit depth , which determines the number of possible digital values that can be used to represent each sample. Early electrical communications started to sample signals in order to multiplex samples from multiple telegraphy sources and to convey them over
738-506: The Bartlane cable picture transmission system used telegraph signaling of characters punched in paper tape to send samples of images quantized to 5 levels. In 1926, Paul M. Rainey of Western Electric patented a facsimile machine that transmitted its signal using 5-bit PCM, encoded by an opto-mechanical analog-to-digital converter . The machine did not go into production. British engineer Alec Reeves , unaware of previous work, conceived
779-630: The SIGSALY encryption equipment, conveyed high-level Allied communications during World War II . In 1943 the Bell Labs researchers who designed the SIGSALY system became aware of the use of PCM binary coding as already proposed by Reeves. In 1949, for the Canadian Navy's DATAR system, Ferranti Canada built a working PCM radio system that was able to transmit digitized radar data over long distances. PCM in
820-474: The public switched telephone network (PSTN) had been largely digitized with very-large-scale integration (VLSI) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges , user-end modems and a wide range of digital transmission applications such as the integrated services digital network (ISDN), cordless telephones and cell phones . PCM is the method of encoding typically used for uncompressed digital audio. In
861-534: The Cat 5 cable in the 8P8C connector: Audio data is transmitted in bidirectional full-duplex mode over two differential pairs used by the 100BASE-TX standard, and word clock sync signal is transmitted over the remaining differential pairs not used by the Fast Ethernet layer. Using separate copper pairs for clock signal simplifies connection setup and allows phase-accurate low- jitter clock sync. AES50 only employs
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#1732859466345902-482: The Ethernet protocol's physical layer (layer 1), relying on Ethernet frames to continuously stream audio data. A proprietary link layer (layer 2) implements a point-to-point audio transmission protocol. It uses a cyclic redundancy check (CRC) for each Ethernet frame and a Hamming code scheme can recover from individual bit errors. The audio data is interleaved so that neighbouring bits belong to different samples, allowing
943-476: The audio data. The HyperMAC protocol is based on the Gigabit Ethernet physical layer for Cat 5e cable (up to 100 m) or OM2 multi-mode fibre (up to 500 m) with embedded clocking . It allows up to 192 bidirectional channels at 96 kHz and 384 channels at 48 kHz; the latency is 4 samples at 96 kHz or 2 samples at 48 kHz, or 41.66 μs. The bandwidth of the auxiliary data link
984-439: The benefits have been debated. The Nyquist–Shannon sampling theorem shows PCM devices can operate without introducing distortions within their designed frequency bands if they provide a sampling frequency at least twice that of the highest frequency contained in the input signal. For example, in telephony , the usable voice frequency band ranges from approximately 300 Hz to 3400 Hz. For effective reconstruction of
1025-445: The channel. In other cases, extra framing bits are added into the stream, which guarantees at least occasional symbol transitions. Another technique used to control ones-density is the use of a scrambler on the data, which will tend to turn the data stream into a stream that looks pseudo-random , but where the data can be recovered exactly by a complementary descrambler. In this case, long runs of zeroes or ones are still possible on
1066-539: The diagram, a sine wave (red curve) is sampled and quantized for PCM. The sine wave is sampled at regular intervals, shown as vertical lines. For each sample, one of the available values (on the y-axis) is chosen. The PCM process is commonly implemented on a single integrated circuit called an analog-to-digital converter (ADC). This produces a fully discrete representation of the input signal (blue points) that can be easily encoded as digital data for storage or manipulation. Several PCM streams could also be multiplexed into
1107-419: The digital domain. These simple techniques have been largely rendered obsolete by modern transform-based audio compression techniques, such as modified discrete cosine transform (MDCT) coding. In telephony, a standard audio signal for a single phone call is encoded as 8,000 samples per second , of 8 bits each, giving a 64 kbit/s digital signal known as DS0 . The default signal compression encoding on
1148-546: The first commercial digital recordings. In 1972, Denon unveiled the first 8-channel digital recorder, the DN-023R, which used a 4-head open reel broadcast video tape recorder to record in 47.25 kHz, 13-bit PCM audio. In 1977, Denon developed the portable PCM recording system, the DN-034R. Like the DN-023R, it recorded 8 channels at 47.25 kHz, but it used 14-bits "with emphasis , making it equivalent to 15.5 bits." In 1979,
1189-437: The first digital pop album, Bop till You Drop , was recorded. It was recorded in 50 kHz, 16-bit linear PCM using a 3M digital tape recorder. The compact disc (CD) brought PCM to consumer audio applications with its introduction in 1982. The CD uses a 44,100 Hz sampling frequency and 16-bit resolution and stores up to 80 minutes of stereo audio per disc. The rapid development and wide adoption of PCM digital telephony
1230-449: The late 1940s and early 1950s used a cathode-ray coding tube with a plate electrode having encoding perforations. As in an oscilloscope , the beam was swept horizontally at the sample rate while the vertical deflection was controlled by the input analog signal, causing the beam to pass through higher or lower portions of the perforated plate. The plate collected or passed the beam, producing current variations in binary code, one bit at
1271-437: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Supermac&oldid=1130556649 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages AES50 AES50 is an Audio over Ethernet protocol for multichannel digital audio . It
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1312-518: The output but are considered unlikely enough to allow reliable synchronization. In other cases, the long term DC value of the modulated signal is important, as building up a DC bias will tend to move communications circuits out of their operating range. In this case, special measures are taken to keep a count of the cumulative DC bias and to modify the codes if necessary to make the DC bias always tend back to zero. Many of these codes are bipolar codes , where
1353-540: The pulses can be positive, negative or absent. In the typical alternate mark inversion code, non-zero pulses alternate between being positive and negative. These rules may be violated to generate special symbols used for framing or other special purposes. The word pulse in the term pulse-code modulation refers to the pulses to be found in the transmission line. This perhaps is a natural consequence of this technique having evolved alongside two analog methods, pulse-width modulation and pulse-position modulation , in which
1394-466: The receiving end to correct burst errors. Specialised cross-point routers can convert multiple point-to-point AES50 links to a centralised star topology . The AES50 protocol supports 24-bit PCM audio and delta-sigma bistream formats ( Direct Stream Digital ), with sample rates that are a multiple of 44.1 or 48 kHz. The bandwidth of 100 Mbit/s allows 48 channels at 48 kHz sample rate, or 24 channels at 96 kHz sample rate. The latency
1435-514: The same title was filed by John R. Pierce in 1945, and issued in 1948: U.S. patent 2,437,707 . The three of them published "The Philosophy of PCM" in 1948. The T-carrier system, introduced in 1961, uses two twisted-pair transmission lines to carry 24 PCM telephone calls sampled at 8 kHz and 8-bit resolution. This development improved capacity and call quality compared to the previous frequency-division multiplexing schemes. In 1973, adaptive differential pulse-code modulation (ADPCM)
1476-565: The use of PCM for voice communication in 1937 while working for International Telephone and Telegraph in France. He described the theory and its advantages, but no practical application resulted. Reeves filed for a French patent in 1938, and his US patent was granted in 1943. By this time Reeves had started working at the Telecommunications Research Establishment . The first transmission of speech by digital techniques,
1517-692: The voice signal even further. An ADPCM algorithm is used to map a series of 8-bit μ-law or A-law PCM samples into a series of 4-bit ADPCM samples. In this way, the capacity of the line is doubled. The technique is detailed in the G.726 standard. Audio coding formats and audio codecs have been developed to achieve further compression. Some of these techniques have been standardized and patented. Advanced compression techniques, such as modified discrete cosine transform (MDCT) and linear predictive coding (LPC), are now widely used in mobile phones , voice over IP (VoIP) and streaming media . PCM can be either return-to-zero (RZ) or non-return-to-zero (NRZ). For
1558-452: The voice signal, telephony applications therefore typically use an 8000 Hz sampling frequency which is more than twice the highest usable voice frequency. Regardless, there are potential sources of impairment implicit in any PCM system: Some forms of PCM combine signal processing with coding. Older versions of these systems applied the processing in the analog domain as part of the analog-to-digital process; newer implementations do so in
1599-447: Was considered for an alternate physical layer in a future revision of AES50, but standardisation did not move forward. Sony licensed its proprietary software implementations of SuperMAC and HyperMAC to Midas Consoles for their Midas XL8 digital mixer. Midas parent Klark Teknik took over the SuperMAC and HyperMAC patents in 2007, then in 2009 Midas and Klark Teknik were acquired by Uli Behringer 's Music Group . The AES50 protocol
1640-560: Was developed, by P. Cummiskey, Nikil Jayant and James L. Flanagan . In 1967, the first PCM recorder was developed by NHK 's research facilities in Japan. The 30 kHz 12-bit device used a compander (similar to DBX Noise Reduction ) to extend the dynamic range, and stored the signals on a video tape recorder . In 1969, NHK expanded the system's capabilities to 2-channel stereo and 32 kHz 13-bit resolution. In January 1971, using NHK's PCM recording system, engineers at Denon recorded
1681-438: Was enabled by metal–oxide–semiconductor (MOS) switched capacitor (SC) circuit technology, developed in the early 1970s. This led to the development of PCM codec-filter chips in the late 1970s. The silicon-gate CMOS (complementary MOS) PCM codec-filter chip, developed by David A. Hodges and W.C. Black in 1980, has since been the industry standard for digital telephony. By the 1990s, telecommunication networks such as