Phonograph Record
The original author of the word phonograph was F.B. Fenby an inventor in Worcester, Massachusetts; he was granted a patent in 1863 for an unsuccessful device called the "Electro-Magnetic Phonograph". His concept detailed a system that would record a sequence of keyboard strokes onto paper tape. Although no model or workable device was ever made, it is often seen as a link to the concept of punched paper for player piano rolls. Arguably, any device used to record sound or reproduce recorded sound could be called a type of "phonograph", but in common practice it has come to mean historic technologies of sound recording. In the late 19th and early 20th century, the alternative term talking machine was sometimes used. The phonograph, or gramophone, was the most common device for playing recorded sound from the 1870s through the 1980s. Usage of these terms is not uniform across the English-speaking world. In more modern usage, this device is often called a turntable, record player, or record changer. The phonograph was the first device for recording and replaying sound.
A gramophone record (also phonograph record, or simply record) is an analogue sound recording medium consisting of a flat disc with an inscribed modulated spiral groove starting near the periphery and ending near the center of the disc. Gramophone records were the primary medium used for commercial music reproduction for most of the 20th century. They replaced the phonograph cylinder as the most popular recording medium in the 1900s, and although they were supplanted in popularity in the late 1980s by digital media, they continue to be manufactured and sold as of 2007.
The terms LP record (LP, 33, or 33-1/3 rpm record), EP, 16-2/3 rpm record (16), 45 rpm record (45), and 78 rpm record (78) each refer to specific types of gramophone records. Except for the LP and EP (which are acronyms of Long Play and Extended Play respectively), these type designations refer to their rotational speeds in revolutions per minute (RPM). LPs, 45s, and 16s are usually made of polyvinyl chloride (PVC), and hence may be referred to as vinyl records or simply vinyl.
Tapes
The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. Although it was originally intended as a medium for dictation, improvements in fidelity led the Compact Cassette to supplant reel-to-reel tape recording in most non-professional applications. Its uses ranged from portable audio to home recording to data storage for early microcomputers. Between the 1960s and early 2000s, the cassette was one of the three most common formats for prerecorded music, alongside the LP and later the Compact Disc. The word cassette is a French word meaning "little box."
Compact Cassettes consist of two miniature spools, between which a magnetic tape is passed and wound. These spools and their attendant parts are held inside a protective plastic shell. Two stereo pairs of tracks (four total) or two monaural audio tracks are available on the tape; one stereo pair or one monophonic track is played or recorded when the tape is moving in one direction and the second pair when moving in the other direction. This reversal is achieved either by manually flipping the cassette or by having the machine itself change the direction of tape movement ("auto-reverse").
Stereo 8, commonly known as the 8-track cartridge, is a magnetic tape technology for audio storage, popular from the mid-1960s to the early 1980s. Stereo 8 was created by a consortium led by Bill Lear in 1964 of the Lear Jet Corporation, along with Ampex, Ford, Motorola, and RCA Records. It followed the similar Stereo-Pak 4-track cartridge. A later quadraphonic version of the format was known as Quad 8 or Q8.
The original format for magnetic tape sound reproduction was reel-to-reel audio tape recording, first made widely available after World War II in the late 1940s. However, threading tape into the recorders was more difficult than simply putting a disc record onto a phonograph player. Manufacturers introduced a succession of cartridges which held the tape inside a metal or plastic housing to eliminate handling. The first was RCA Victor, which in 1958 introduced a cartridge system, but until the introduction of the Compact Cassette in 1963 and Stereo 8 in 1964, none was very successful.
Compact Disc
A Compact Disc or CD is an optical disc used to store digital data, originally developed for storing digital audio. The CD, available on the market in late 1982, remains the standard physical medium for commercial audio recordings as of 2007. An audio CD consists of one or more stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. Standard CDs have a diameter of 120 mm and can hold approximately 80 minutes of audio. There are also 80 mm discs, sometimes used for CD singles, which hold approximately 20 minutes of audio. Compact Disc technology was later adapted for use as a data storage device, known as a CD-ROM, and to include record-once and re-writable media (CD-R and CD-RW respectively). CD-ROMs and CD-Rs remain widely used technologies in the Computer industry as of 2007. The CD and its extensions have been extremely successful: in 2004, the annual worldwide sales of CD-Audio, CD-ROM, and CD-R reached about 30 billion discs.
The Compact Disc reached the market in late 1982 in Asia, and early the following year in the United States and other markets. The first CDs available were 16 Japanese-made titles from CBS/Sony. This event is often seen as the "Big Bang" of the digital audio revolution. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities and its handling quality received particular praise. As the price of players sank rapidly, the CD began to gain popularity in the larger popular and rock music markets.
The CD was originally thought of as an evolution of the gramophone record, rather than primarily as a data storage medium. Only later did the concept of an 'audio file' arise, and the generalizing of this to any data file. From its origins as a music format, Compact Disc has grown to encompass other applications. In June 1985, the CD-ROM (read-only memory) and, in 1990, CD-Recordable was introduced, also developed by Sony and Philips. While CDs are significantly more durable than earlier audio formats, they are susceptible to damage from daily usage and environmental factors.
MP3
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular audio encoding format. It uses a loosy compression algorithm that is designed to greatly reduce the amount of data required to represent the audio recording, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. It was invented by a team of European engineers.
MP3 is an audio-specific format. The compression takes off certain sounds that cannot be heard by the listener, i.e. outside the normal human hearing range. It provides a representation of pulse-code modulation encoded audio in much less space than straightforward methods, by using psychoacoustic models to discard components less audible to human hearing, and recording the remaining information in an efficient manner. Similar principles are used by JPEG, an image compression format.
Modern lossy bit compression technologies, including MPEG, MP3, etc, are based on the early work of Prof Oscar Bonello of the University of Buenos Aires, Argentina. He was involved in Studio equipment design for Broadcast radio automation. At the same time he taught Acoustics at the University, Psychoacoustics being his main field of research. In 1983 he started researching the idea of using the Critical Band Masking principle (a property of the ear) in order to reduce the bit stream needed to encode an audio signal. The masking principle was discovered in 1924 and further developed by in 1959. Bonello's work created, in 1987, the world's first bit compression system, named ECAM, working in real time and implemented by hardware on an IBM PC computer. This plug in card and the associated control software was demonstrated for the first time in 1988 as a fully working product named Audicom and introduced to the world at the international NAB Radio Exhibition in Atlanta, USA on 1990. The basic Bonello implementation is now used in MP3 and other systems. Bonello refuses to apply for any patents around this technology.
A reference simulation software implementation, written in the C language and known as ISO 11172-5, was developed by the members of the ISO MPEG Audio committee in order to produce bit compliant MPEG Audio files (Layer 1, Layer 2, Layer 3). Working in non-real time on a number of operating systems, it was able to demonstrate the first real time hardware decoding (DSP based) of compressed audio. Some other real time implementation of MPEG Audio encoders were available for the purpose of digital broadcasting (radio DAB, television DVB) towards consumer receivers and set top boxes.
Later, on July 7, 1994 the Fraunhofer Society released the first software MP3 encoder called l3enc. The filename extension .mp3 was chosen by the Fraunhofer team on July 14, 1995 (previously, the files had been named .bit). With the first real-time software MP3 player Winplay3 (released September 9, 1995) many people were able to encode and playback MP3 files on their PCs. Because of the relatively small hard drives back in that time (500 MB) the technology was essential to store non-instrument based music for listening on a computer.
In October 1993, MP2 (MPEG-1 Audio Layer 2) files appeared on the Internet and were often played back using the Xing MPEG Audio Player, and later in a program for Unix by Tobias Bading called MAPlay, which was initially released on February 22, 1994 (MAPlay was also ported to Microsoft Windows).
Initially the only encoder available for MP2 production was the Xing Encoder, accompanied by the program cdda2wav, a CD ripper used for extracting CD audio tracks to Waveform Audio Files.The Internet Underground Music Archive (IUMA) is generally recognized as the start of the on-line music revolution. IUMA was the Internet's first high-fidelity music web site, hosting thousands of authorized MP2 recordings before MP3 or the web was popularized.
In the first half of 1995 through the late 1990s, MP3 files began to spread on the Internet. MP3's popularity began to rise rapidly with the advent of Nullsoft's audio player Winamp (released in 1997), the UNIX audio player mpg123 and the peer-to-peer file sharing network Napster (released in 1999). These programs made it simple for average users to play back, create, share and collect MP3s.
The small size of MP3 files has enabled widespread peer-to-peer file sharing of music, which would previously have been near impossible. The major record companies, who argue that such free sharing of music reduces sales, reacted to this by pursuing law-suits against Napster, which was eventually closed down, and eventually against individual users who engaged in file sharing.
Despite the popularity of MP3, online music retailers often use other proprietary formats that are encrypted (known as Digital Rights Management) to prevent users from using purchased music in ways not specifically authorized by the record companies. The record companies argue that this is necessary to prevent the files from being made available on peer-to-peer file sharing networks. However, this has other side effects such as preventing users from playing back their purchased music on different types of devices. Some services, such as eMusic, continue to offer the MP3 format, which allows users to playback their music on virtually any device.
When creating an MP3 file, there is a trade-off between the amount of space used and the sound quality of the result. Typically, the creator of the MP3 file is allowed to set a bit rate, which specifies how many kilobits the file may use per second of audio, for example, when ripping a compact disc to this format. The lower the bit rate used, the lower the audio quality will be, but the smaller the file size. Likewise, the higher the bit rate used, the higher quality, and therefore, larger the file size the resulting MP3 will be.
As described, MP3 files encoded with a lower bit rate will generally play back at a lower quality. With too low a bit rate, "compression artifacts" (i.e., sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to compress because of its randomness and sharp attacks. When this type of audio is compressed, artifacts such as ringing or pre-echo are usually heard. A sample of applause compressed with a relatively nominal bit rate provides a good example of compression artifacts.
Besides the bit rate of an encoded piece of audio, the quality of MP3 files also depends on the quality of the encoder itself, and the difficulty of the signal being encoded. As the MP3 standard allows quite a bit of freedom with encoding algorithms, different encoders may feature quite different quality, even when targeting similar bit rates.
Quality is heavily dependent on the choice of encoder and encoding parameters. While quality around 128kbps was somewhere between annoying and acceptable with older encoders, modern MP3 encoders can provide very good quality at those bit rates.
The advances in this technology is exploding as is the quality of the devices, will our grandchildren be as shocked at our current media as we are with our grandparents?
No comments:
Post a Comment