AmpliFIND is an acoustic fingerprinting service and a software development kit developed by the US company MusicIP .
49-490: MusicIP first marketed their fingerprinting algorithm and service as MusicDNS . In 2006, MusicIP reported that the MusicDNS database had more than 22 million fingerprints of digital audio recordings. One of their customers was MetaBrainz Foundation , a non-profit company that used MusicDNS in their MusicBrainz and MusicBrainz Picard software products. Even so, MusicIP dissolved in 2008. The company's CEO, Andrew Stess, bought
98-422: A data compression algorithm. Adaptive DPCM (ADPCM) was introduced by P. Cummiskey, Nikil S. Jayant and James L. Flanagan at Bell Labs in 1973. Perceptual coding was first used for speech coding compression, with linear predictive coding (LPC). Initial concepts for LPC date back to the work of Fumitada Itakura ( Nagoya University ) and Shuzo Saito ( Nippon Telegraph and Telephone ) in 1966. During
147-462: A digital system do not result in error unless they are so large as to result in a symbol being misinterpreted as another symbol or disturbing the sequence of symbols. It is, therefore, generally possible to have an entirely error-free digital audio system in which no noise or distortion is introduced between conversion to digital format and conversion back to analog. A digital audio signal may be encoded for correction of any errors that might occur in
196-489: A DAC. According to the Nyquist–Shannon sampling theorem , with some practical and theoretical restrictions, a band-limited version of the original analog signal can be accurately reconstructed from the digital signal. During conversion, audio data can be embedded with a digital watermark to prevent piracy and unauthorized use. Watermarking is done using a direct-sequence spread-spectrum (DSSS) method. The audio information
245-534: A computer program to retrieve identifying information (such as the song title and recording artist) from the MusicDNS database. The PUID code is a short, alphanumeric string based on the universally unique identifier standard. The source code for LibOFA is distributed under a dual license : the GNU General Public License and the Adaptive Public License . The MusicDNS software that makes
294-537: A different sampling rate to a common sampling rate prior to processing. Audio data compression techniques, such as MP3 , Advanced Audio Coding (AAC), Opus , Ogg Vorbis , or FLAC , are commonly employed to reduce the file size. Digital audio can be carried over digital audio interfaces such as AES3 or MADI . Digital audio can be carried over a network using audio over Ethernet , audio over IP or other streaming media standards and systems. For playback, digital audio must be converted back to an analog signal with
343-480: A digital file gives an exact copy if the equipment is operating properly which eliminates generation loss caused by copying, while reencoding digital files with lossy compression codecs can cause generation loss. This trait of digital technology has given rise to awareness of the risk of unauthorized copying. Before digital technology was widespread, a record label , for example, could be confident knowing that unauthorized copies of their music tracks were never as good as
392-514: A large number of channels at once; in the extreme case, for example with a 48-track recording studio, an entire complex mixdown could be done in a single generation, although this was prohibitively expensive for all but the best-funded projects. The introduction of professional analog noise reduction systems such as Dolby A helped reduce the amount of audible generation loss, but were eventually superseded by digital systems which vastly reduced generation loss. According to ATIS , "Generation loss
441-432: A low-resolution digital image for a web page is better if generated from an uncompressed raw image than from an already-compressed JPEG file of higher quality. In digital systems , several techniques such as lossy compression codecs and algorithms, used because of other advantages, may introduce generation loss and must be used with caution. However, copying a digital file itself incurs no generation loss—the copied file
490-522: A range of digital transmission applications such as the integrated services digital network (ISDN), cordless telephones and cell phones . Digital audio is used in broadcasting of audio. Standard technologies include Digital audio broadcasting (DAB), Digital Radio Mondiale (DRM), HD Radio and In-band on-channel (IBOC). Digital audio in recording applications is stored on audio-specific technologies including CD, DAT, Digital Compact Cassette (DCC) and MiniDisc . Digital audio may be stored in
539-515: A similar function with Hi8 tapes. Formats like ProDigi and DASH were referred to as SDAT (stationary-head digital audio tape) formats, as opposed to formats like the PCM adaptor-based systems and Digital Audio Tape (DAT), which were referred to as RDAT (rotating-head digital audio tape) formats, due to their helical-scan process of recording. Like the DAT cassette, ProDigi and DASH machines also accommodated
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#1732869712616588-442: A specified sampling rate and converts at a known bit resolution. CD audio , for example, has a sampling rate of 44.1 kHz (44,100 samples per second), and has 16-bit resolution for each stereo channel. Analog signals that have not already been bandlimited must be passed through an anti-aliasing filter before conversion, to prevent the aliasing distortion that is caused by audio signals with frequencies higher than
637-442: A standard audio file formats and stored on a Hard disk recorder , Blu-ray or DVD-Audio . Files may be played back on smartphones, computers or MP3 player . Digital audio resolution is measured in audio bit depth . Most digital audio formats use either 16-bit, 24-bit, and 32-bit resolution. Generation loss Generation loss is the loss of quality between subsequent copies or transcodes of data. Anything that reduces
686-405: Is by using uncompressed or losslessly compressed files; which may be expensive from a storage standpoint as they require larger amounts of storage space in flash memory or hard drives per second of runtime. Uncompressed video requires a high data rate; for example, a 1080p video at 60 frames per second require approximately 370 megabytes per second. Lossy codecs make Blu-rays and streaming video over
735-458: Is identical to the original, provided a perfect copying channel is used. Some digital transforms are reversible, while some are not. Lossless compression is, by definition, fully reversible, while lossy compression throws away some data which cannot be restored. Similarly, many DSP processes are not reversible. Thus careful planning of an audio or video signal chain from beginning to end and rearranging to minimize multiple conversions
784-404: Is important to avoid generation loss when using lossy compression codecs. Often, arbitrary choices of numbers of pixels and sampling rates for source, destination, and intermediates can seriously degrade digital signals in spite of the potential of digital technology for eliminating generation loss completely. Similarly, when using lossy compression, it will ideally only be done once, at the end of
833-428: Is limited to analog recording because digital recording and reproduction may be performed in a manner that is essentially free from generation loss." Used correctly, digital technology can eliminate generation loss. This implies the exclusive use of lossless compression codecs or uncompressed data from recording or creation until the final lossy encode for distribution through internet streaming or optical discs. Copying
882-465: Is then modulated by a pseudo-noise (PN) sequence, then shaped within the frequency domain and put back in the original signal. The strength of the embedding determines the strength of the watermark on the audio data. Pulse-code modulation (PCM) was invented by British scientist Alec Reeves in 1937. In 1950, C. Chapin Cutler of Bell Labs filed the patent on differential pulse-code modulation (DPCM),
931-577: Is then sent through an audio power amplifier and ultimately to a loudspeaker . Digital audio systems may include compression , storage , processing , and transmission components. Conversion to a digital format allows convenient manipulation, storage, transmission, and retrieval of an audio signal. Unlike analog audio, in which making copies of a recording results in generation loss and degradation of signal quality, digital audio allows an infinite number of copies to be made without any degradation of signal quality. Digital audio technologies are used in
980-547: The Nyquist frequency (half the sampling rate). A digital audio signal may be stored or transmitted. Digital audio can be stored on a CD, a digital audio player , a hard drive , a USB flash drive , or any other digital data storage device . The digital signal may be altered through digital signal processing , where it may be filtered or have effects applied. Sample-rate conversion including upsampling and downsampling may be used to change signals that have been encoded with
1029-700: The United States was made by Thomas Stockham at the Santa Fe Opera in 1976, on a Soundstream recorder. An improved version of the Soundstream system was used to produce several classical recordings by Telarc in 1978. The 3M digital multitrack recorder in development at the time was based on BBC technology. The first all-digital album recorded on this machine was Ry Cooder 's Bop till You Drop in 1979. British record label Decca began development of its own 2-track digital audio recorders in 1978 and released
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#17328697126161078-434: The 1970s, Bishnu S. Atal and Manfred R. Schroeder at Bell Labs developed a form of LPC called adaptive predictive coding (APC), a perceptual coding algorithm that exploited the masking properties of the human ear, followed in the early 1980s with the code-excited linear prediction (CELP) algorithm. Discrete cosine transform (DCT) coding, a lossy compression method first proposed by Nasir Ahmed in 1972, provided
1127-632: The Open Fingerprint Architecture, a specification developed during 2000–05 by MusicIP's previous incarnation, Predixis Corporation. Through LibOFA, a program can fingerprint a recording, and submit the fingerprint to MusicDNS via the Internet. MusicDNS attempts to match the submission to fingerprints in its database. If the MusicDNS service finds an approximate match, it returns a code called a PUID (Portable Unique Identifier). This code does not contain any acoustic information; rather, it enables
1176-487: The audio data being recorded to the tape using a multi-track stationary tape head. PCM adaptors allowed for stereo digital audio recording on a conventional NTSC or PAL video tape recorder . The 1982 introduction of the CD by Philips and Sony popularized digital audio with consumers. ADAT became available in the early 1990s, which allowed eight-track 44.1 or 48 kHz recording on S-VHS cassettes, and DTRS performed
1225-466: The basis for the modified discrete cosine transform (MDCT), which was developed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987. The MDCT is the basis for most audio coding standards , such as Dolby Digital (AC-3), MP3 ( MPEG Layer III), AAC, Windows Media Audio (WMA), Opus and Vorbis ( Ogg ). PCM was used in telecommunications applications long before its first use in commercial broadcast and recording. Commercial digital recording
1274-482: The computer can effectively run at a single time. Avid Audio and Steinberg released the first digital audio workstation software programs in 1989. Digital audio workstations make multitrack recording and mixing much easier for large projects which would otherwise be difficult with analog equipment. The rapid development and wide adoption of PCM digital telephony was enabled by metal–oxide–semiconductor (MOS) switched capacitor (SC) circuit technology, developed in
1323-407: The copy over an analog connection), generation loss is mostly due to noise and bandwidth issues in cables , amplifiers , mixers , recording equipment and anything else between the source and the destination. Poorly adjusted distribution amplifiers and mismatched impedances can make these problems even worse. Repeated conversion between analog and digital can also cause loss. Generation loss
1372-570: 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 the public switched telephone network (PSTN) had been largely digitized with VLSI (very large-scale integration ) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges , user-end modems and
1421-409: The electrical audio signal is amplified and then converted back into physical waveforms via a loudspeaker . Analog audio retains its fundamental wave-like characteristics throughout its storage, transformation, duplication, and amplification. Analog audio signals are susceptible to noise and distortion, due to the innate characteristics of electronic circuits and associated devices. Disturbances in
1470-451: The end. Often, particular implementations fall short of theoretical ideals. Successive generations of photocopies result in image distortion and degradation. Repeatedly downloading and then reposting / reuploading content to platforms such as Instagram or YouTube can result to noticeable quality degradation. Similar effects have been documented in copying of VHS tapes. This is because both services use lossy codecs on all data that
1519-450: The fingerprints is proprietary . 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 resolution . Digital audio is also
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1568-399: The first European digital recording in 1979. Popular professional digital multitrack recorders produced by Sony/Studer ( DASH ) and Mitsubishi ( ProDigi ) in the early 1980s helped to bring about digital recording's acceptance by the major record companies. Machines for these formats had their own transports built-in as well, using reel-to-reel tape in either 1/4", 1/2", or 1" widths, with
1617-422: The internet feasible since neither can deliver the amounts of data needed for uncompressed or losslessly compressed video at acceptable frame rates and resolutions. Images can suffer from generation loss in the same way video and audio can. Processing a lossily compressed file rather than an original usually results in more loss of quality than generating the same output from an uncompressed original. For example,
1666-399: The most common form of music consumption. An analog audio system converts physical waveforms of sound into electrical representations of those waveforms by use of a transducer , such as a microphone . The sounds are then stored on an analog medium such as magnetic tape , or transmitted through an analog medium such as a telephone line or radio . The process is reversed for reproduction:
1715-415: The music industry distributed and sold music by selling physical copies in the form of records and cassette tapes . With digital audio and online distribution systems such as iTunes , companies sell digital sound files to consumers, which the consumer receives over the Internet. Popular streaming services such as Apple Music , Spotify , or YouTube , offer temporary access to the digital file, and are now
1764-446: 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
1813-578: The obligatory 44.1 kHz sampling rate, but also 48 kHz on all machines, and eventually a 96 kHz sampling rate. They overcame the problems that made typical analog recorders unable to meet the bandwidth (frequency range) demands of digital recording by a combination of higher tape speeds, narrower head gaps used in combination with metal-formulation tapes, and the spreading of data across multiple parallel tracks. Unlike analog systems, modern digital audio workstations and audio interfaces allow as many channels in as many different sampling rates as
1862-484: The originals. Generation loss can still occur when using lossy video or audio compression codecs as these introduce artifacts into the source material with each encode or reencode. Lossy compression codecs such as Apple ProRes , Advanced Video Coding and mp3 are very widely used as they allow for dramatic reductions on file size while being indistinguishable from the uncompressed or losslessly compressed original for viewing purposes. The only way to avoid generation loss
1911-412: The quality of the representation when copying, and would cause further reduction in quality on making a copy of the copy, can be considered a form of generation loss. File size increases are a common result of generation loss, as the introduction of artifacts may actually increase the entropy of the data through each generation. In analog systems (including systems that use digital recording but make
1960-701: The quality setting will cause different quantization constants to be used, causing additional loss. Further, as JPEG is divided into 16×16 blocks (or 16×8, or 8×8, depending on chroma subsampling ), cropping that does not fall on an 8×8 boundary shifts the encoding blocks, causing substantial degradation – similar problems happen on rotation. This can be avoided by the use of jpegtran or similar tools for cropping. Similar degradation occurs if video keyframes do not line up from generation to generation. Digital resampling such as image scaling , and other DSP techniques can also introduce artifacts or degrade signal-to-noise ratio (S/N ratio) each time they are used, even if
2009-453: The recording, manipulation, mass-production, and distribution of sound, including recordings of songs , instrumental pieces, podcasts , sound effects, and other sounds. Modern online music distribution depends on digital recording and data compression . The availability of music as data files, rather than as physical objects, has significantly reduced the costs of distribution as well as making it easier to share copies. Before digital audio,
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2058-507: The rights to MusicDNS, renamed the software to AmpliFIND , and started a new company called AmpliFIND Music Services. In 2011, Stess sold AmpliFIND to Sony , who incorporated it into the digital music service offerings of their Gracenote division. Tribune Media subsequently purchased Gracenote, including the MusicDNS software. To use the MusicDNS service, software developers write a computer program that incorporates an open-source software library called LibOFA. This library implements
2107-882: The signal is decoded and then re-encoded with identical settings, there is no loss, and scalable, meaning that if it is re-encoded with lower quality settings, the result will be the same as if it had been encoded from the original signal – see Scalable Video Coding . More generally, transcoding between different parameters of a particular encoding will ideally yield the greatest common shared quality – for instance, converting from an image with 4 bits of red and 8 bits of green to one with 8 bits of red and 4 bits of green would ideally yield simply an image with 4 bits of red color depth and 4 bits of green color depth without further degradation. Some lossy compression algorithms are much worse than others in this regard, being neither idempotent nor scalable, and introducing further degradation if parameters are changed. For example, with JPEG , changing
2156-420: 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 , audio playback machines, and other digital tools. For playback, a digital-to-analog converter (DAC) performs the reverse process, converting a digital signal back into an analog signal, which
2205-400: The storage or transmission of the signal. This technique, known as channel coding , is essential for broadcast or recorded digital systems to maintain bit accuracy. Eight-to-fourteen modulation is the channel code used for the audio compact disc (CD). If an audio signal is analog, a digital audio system starts with an ADC that converts an analog signal to a digital signal. The ADC runs at
2254-540: The underlying storage is lossless. Resampling causes aliasing , both blurring low-frequency components and adding high-frequency noise, causing jaggies , while rounding off computations to fit in finite precision introduces quantization , causing banding ; if fixed by dither , this instead becomes noise. In both cases, these at best degrade the signal's S/N ratio, and may cause artifacts. Quantization can be reduced by using high precision while editing (notably floating point numbers), only reducing back to fixed precision at
2303-514: The workflow involving the file, after all required changes have been made. Converting between lossy formats – be it decoding and re-encoding to the same format, between different formats, or between different bitrates or parameters of the same format – causes generation loss. Repeated applications of lossy compression and decompression can cause generation loss, particularly if the parameters used are not consistent across generations. Ideally an algorithm will be both idempotent , meaning that if
2352-428: Was a major consideration in complex analog audio and video editing , where multi-layered edits were often created by making intermediate mixes which were then "bounced down" back onto tape. Careful planning was required to minimize generation loss, and the resulting noise and poor frequency response. One way of minimizing the number of generations needed was to use an audio mixing or video editing suite capable of mixing
2401-495: Was pioneered in Japan by NHK and Nippon Columbia and their Denon brand, in the 1960s. The first commercial digital recordings were released in 1971. The BBC also began to experiment with digital audio in the 1960s. By the early 1970s, it had developed a 2-channel recorder, and in 1972 it deployed a digital audio transmission system that linked their broadcast center to their remote transmitters. The first 16-bit PCM recording in
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