MP3

qas: question: What is the common name for MPEG-2 Audio Layer III?
answers: text: MP3

question: What kind of audio is the coding format for?
answers: text: digital

question: Other than storage, what is the common audio format used for?
answers: text: consumer audio streaming

question: What does MP3 use to format it's data?
answers: text: lossy data compression

question: Where will MP3 files most commonly be found?
answers: text: digital audio players
context: MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is an audio coding format for digital audio which uses a form of lossy data compression. It is a common audio format for consumer audio streaming or storage, as well as a de facto standard of digital audio compression for the transfer and playback of music on most digital audio players.

qas: question: What is the main goal aside from reducing the amount of data required to store the audio?
answers: text: sound like a faithful reproduction

question: What kind of compression is used?
answers: text: created

question: If a file is created using 128 kbit/s, what size is the file going to be compared to a CD?
answers: text: 1/11

question: How many total bit/s would a CD have?
answers: text: 1,411,200

question: How many total bit/s would an MP3 compressed at 128 kbit/s have?
answers: text: 128,000
context: The use of lossy compression is designed to greatly reduce the amount of data required to represent the audio recording and still sound like a faithful reproduction of the original uncompressed audio for most listeners. An MP3 file that is created using the setting of 128 kbit/s will result in a file that is about 1/11 the size of the CD file created from the original audio source (44,100 samples per second × 16 bits per sample × 2 channels = 1,411,200 bit/s; MP3 compressed at 128 kbit/s: 128,000 bit/s [1 k = 1,000, not 1024, because it is a bit rate]. Ratio: 1,411,200/128,000 = 11.025). An MP3 file can also be constructed at higher or lower bit rates, with higher or lower resulting quality.

qas: question: What does the compression target in the song?
answers: text: accuracy

question: The targetting focuses on what aspect that is beyond the ability of most people?
answers: text: auditory resolution

question: What is this method commonly referred to as?
answers: text: perceptual coding

question: What kind of model is used in this kind of compression?
answers: text: psychoacoustic

question: These models ensure that the precision is reduced for the components that are what to human hearing?
answers: text: less audible
context: The compression works by reducing the accuracy of certain parts of a sound that are considered to be beyond the auditory resolution ability of most people. This method is commonly referred to as perceptual coding. It uses psychoacoustic models to discard or reduce precision of components less audible to human hearing, and then records the remaining information in an efficient manner.

qas: question: Who designed MP3?
answers: text: Moving Picture Experts Group

question: What was the first standard that this group had?
answers: text: MPEG-1

question: The first standard later developed into which standard?
answers: text: MPEG-2

question: When was the draft passed to have MPEG-1 Audio approved as a standard?
answers: text: 1991

question: When was MPEG-2 Audio finally published?
answers: text: 1995
context: MP3 was designed by the Moving Picture Experts Group (MPEG) as part of its MPEG-1 standard and later extended in the MPEG-2 standard. The first subgroup for audio was formed by several teams of engineers at Fraunhofer IIS, University of Hannover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others. MPEG-1 Audio (MPEG-1 Part 3), which included MPEG-1 Audio Layer I, II and III was approved as a committee draft of ISO/IEC standard in 1991, finalised in 1992 and published in 1993 (ISO/IEC 11172-3:1993). Backwards compatible MPEG-2 Audio (MPEG-2 Part 3) with additional bit rates and sample rates was published in 1995 (ISO/IEC 13818-3:1995).

qas: question: What does the MP3 compression take advantage of?
answers: text: perceptual limitation

question: What is the limitation in human hearing referred to as?
answers: text: auditory masking

question: Who was the physicist to report that a tone could be rendered inaudible.
answers: text: Alfred M. Mayer

question: When were audio curves described by Richard Ehmer?
answers: text: 1959

question: The initial work was aimed at determining critical ratios and what else?
answers: text: critical bandwidths
context: The MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be rendered inaudible by another tone of lower frequency. In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Ernst Terhardt et al. created an algorithm describing auditory masking with high accuracy. This work added to a variety of reports from authors dating back to Fletcher, and to the work that initially determined critical ratios and critical bandwidths.

qas: question: What was first proposed in 1979?
answers: text: The psychoacoustic masking codec

question: Which country were the researchers located in?
answers: text: United States

question: Who was the first to produce hardware for speech?
answers: text: Krasner

question: What does LPC stand for?
answers: text: linear predictive coding

question: What was reported in IEEE's Journal on Selected Areas in Communications?
answers: text: audio compression algorithms
context: The psychoacoustic masking codec was first proposed in 1979, apparently independently, by Manfred R. Schroeder, et al. from Bell Telephone Laboratories, Inc. in Murray Hill, NJ, and M. A. Krasner both in the United States. Krasner was the first to publish and to produce hardware for speech (not usable as music bit compression), but the publication of his results as a relatively obscure Lincoln Laboratory Technical Report did not immediately influence the mainstream of psychoacoustic codec development. Manfred Schroeder was already a well-known and revered figure in the worldwide community of acoustical and electrical engineers, but his paper was not much noticed, since it described negative results due to the particular nature of speech and the linear predictive coding (LPC) gain present in speech. Both Krasner and Schroeder built upon the work performed by Eberhard F. Zwicker in the areas of tuning and masking of critical bands, that in turn built on the fundamental research in the area from Bell Labs of Harvey Fletcher and his collaborators. A wide variety of (mostly perceptual) audio compression algorithms were reported in IEEE's refereed Journal on Selected Areas in Communications. That journal reported in February 1988 on a wide range of established, working audio bit compression technologies, some of them using auditory masking as part of their fundamental design, and several showing real-time hardware implementations.

qas: question: What does OCF stand for?
answers: text: Optimum Coding in the Frequency Domain

question: What does PXFM stand for?
answers: text: Perceptual Transform Coding

question: What was the name of the codec that OCF, PFXM and other contributes merged into?
answers: text: ASPEC

question: Which competition did ASPEC win?
answers: text: quality

question: What was the first practical implementation based on?
answers: text: Motorola 56000 DSP chips
context: The immediate predecessors of MP3 were "Optimum Coding in the Frequency Domain" (OCF), and Perceptual Transform Coding (PXFM). These two codecs, along with block-switching contributions from Thomson-Brandt, were merged into a codec called ASPEC, which was submitted to MPEG, and which won the quality competition, but that was mistakenly rejected as too complex to implement. The first practical implementation of an audio perceptual coder (OCF) in hardware (Krasner's hardware was too cumbersome and slow for practical use), was an implementation of a psychoacoustic transform coder based on Motorola 56000 DSP chips.

qas: question: What kind of student was Karlheinz Brandenburg?
answers: text: doctoral

question: When did Karlheinz start working on digitmal music compression?
answers: text: early 1980s

question: Where did Bradenburg become an assistant professor at?
answers: text: Erlangen-Nuremberg

question: Who did Brandenburg work with in music compression?
answers: text: Fraunhofer Society

question: When did Brandenburg join the Fraunhofen Institute?
answers: text: 1993
context: As a doctoral student at Germany's University of Erlangen-Nuremberg, Karlheinz Brandenburg began working on digital music compression in the early 1980s, focusing on how people perceive music. He completed his doctoral work in 1989. MP3 is directly descended from OCF and PXFM, representing the outcome of the collaboration of Brandenburg—working as a postdoc at AT&T-Bell Labs with James D. Johnston ("JJ") of AT&T-Bell Labs—with the Fraunhofer Institut for Integrated Circuits, Erlangen, with relatively minor contributions from the MP2 branch of psychoacoustic sub-band coders. In 1990, Brandenburg became an assistant professor at Erlangen-Nuremberg. While there, he continued to work on music compression with scientists at the Fraunhofer Society (in 1993 he joined the staff of the Fraunhofer Institute).

qas: question: What was the name of the first song used to develop the MP3?
answers: text: Tom's Diner

question: Who was the artist of the first song used?
answers: text: Suzanne Vega

question: Who adjusted the song?
answers: text: Karlheinz Brandenburg

question: The song was listened to multiple times to try and refine what?
answers: text: scheme

question: What particular aspect of the artists voice was he trying to preserve?
answers: text: subtlety
context: The song "Tom's Diner" by Suzanne Vega was the first song used by Karlheinz Brandenburg to develop the MP3. Brandenburg adopted the song for testing purposes, listening to it again and again each time refining the scheme, making sure it did not adversely affect the subtlety of Vega's voice.

qas: question: How many proposals were available in 1991?
answers: text: two

question: Other than ASPEC what was another proposal?
answers: text: Musicam

question: The Musicam format was proposed by Philips, based in which country?
answers: text: Netherlands

question: Which other quality alongside simplicty was key in selecting this proposal?
answers: text: error robustness

question: What was the Musican format based on?
answers: text: sub-band coding
context: In 1991, there were only two proposals available that could be completely assessed for an MPEG audio standard: Musicam (Masking pattern adapted Universal Subband Integrated Coding And Multiplexing) and ASPEC (Adaptive Spectral Perceptual Entropy Coding). The Musicam technique, as proposed by Philips (the Netherlands), CCETT (France) and Institut für Rundfunktechnik (Germany) was chosen due to its simplicity and error robustness, as well as its low computational power associated with the encoding of high quality compressed audio. The Musicam format, based on sub-band coding, was the basis of the MPEG Audio compression format (sampling rates, structure of frames, headers, number of samples per frame).

qas: question: What was only incorporated into Layer III and not Layers I or II?
answers: text: filter bank

question: Who was the chair that oversaw the editing of the standard?
answers: text: Professor Musmann

question: Who's responsibility was it to edit the standard for Layer I?
answers: text: Leon van de Kerkhof

question: Who's responsibility was it to edit the standard for Layer II?
answers: text: Gerhard Stoll
context: Much of its technology and ideas were incorporated into the definition of ISO MPEG Audio Layer I and Layer II and the filter bank alone into Layer III (MP3) format as part of the computationally inefficient hybrid filter bank. Under the chairmanship of Professor Musmann (University of Hannover) the editing of the standard was made under the responsibilities of Leon van de Kerkhof (Layer I) and Gerhard Stoll (Layer II).

qas: question: What was the name given to the proposal?
answers: text: ASPEC

question: What did the joint proposal provide?
answers: text: the highest coding efficiency

question: Other than Thomson Consumer Electronics, Fraunhofer Society and CNET, who else was a part of the joint proposal?
answers: text: AT&T Bell Laboratories
context: ASPEC was the joint proposal of AT&T Bell Laboratories, Thomson Consumer Electronics, Fraunhofer Society and CNET. It provided the highest coding efficiency.

qas: question: What did the working group take ideas from?
answers: text: ASPEC

question: What did the working group integrate their ideas with?
answers: text: filter bank

question: Where was the filter bank taken from?
answers: text: Layer 2

question: What did the working group eventually create?
answers: text: MP3

question: What quality were they hoping to match at 128 kbit/s?
answers: text: MP2 at 192 kbit/s
context: A working group consisting of Leon van de Kerkhof (The Netherlands), Gerhard Stoll (Germany), Leonardo Chiariglione (Italy), Yves-François Dehery (France), Karlheinz Brandenburg (Germany) and James D. Johnston (USA) took ideas from ASPEC, integrated the filter bank from Layer 2, added some of their own ideas and created MP3, which was designed to achieve the same quality at 128 kbit/s as MP2 at 192 kbit/s.

qas: question: When were the algorithms approved?
answers: text: 1991

question: When were the approved algorithms finalized?
answers: text: 1992

question: What was the first started suite by MPEG?
answers: text: MPEG-1

question: What was the official name of the internation standard?
answers: text: ISO/IEC 11172-3

question: When was the international standard published?
answers: text: 1993
context: All algorithms for MPEG-1 Audio Layer I, II and III were approved in 1991 and finalized in 1992 as part of MPEG-1, the first standard suite by MPEG, which resulted in the international standard ISO/IEC 11172-3 (a.k.a. MPEG-1 Audio or MPEG-1 Part 3), published in 1993.

qas: question: Further work on MPEG was finalized as a part of which MPEG standard?
answers: text: second suite

question: What was the official name of ISO/IEC 13818-3 better known as?
answers: text: MPEG-2

question: At what rate were the new sampling rates defined in comparison to MPEG-1 Audio?
answers: text: half

question: Apart from cutting the frequency fidelity in half, what else was cut in half?
answers: text: bitrate

question: Allowing the coding of audio programs with more than two channels was a major aspect of what?
answers: text: MPEG-2 Part 3
context: Further work on MPEG audio was finalized in 1994 as part of the second suite of MPEG standards, MPEG-2, more formally known as international standard ISO/IEC 13818-3 (a.k.a. MPEG-2 Part 3 or backwards compatible MPEG-2 Audio or MPEG-2 Audio BC), originally published in 1995. MPEG-2 Part 3 (ISO/IEC 13818-3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sampling rates are exactly half that of those originally defined in MPEG-1 Audio. This reduction in sampling rate serves to cut the available frequency fidelity in half while likewise cutting the bitrate by 50%. MPEG-2 Part 3 also enhanced MPEG-1's audio by allowing the coding of audio programs with more than two channels, up to 5.1 multichannel.

qas: question: As MPEG-3 had a different meaning, what was the name given to the extension of MPEG-2?
answers: text: MPEG-2.5 audio

question: Where was this extension developed?
answers: text: Fraunhofer IIS

question: The new sampling rates widened the scope of MP3 to be able to include what?
answers: text: human speech

question: What is not an ISO recognized standard?
answers: text: MPEG-2.5

question: As MPEG-2.5 is unofficial, it is considered what kind of extension to the MP3 format?
answers: text: proprietary
context: An additional extension to MPEG-2 is named MPEG-2.5 audio, as MPEG-3 already had a different meaning. This extension was developed at Fraunhofer IIS, the registered MP3 patent holders. Like MPEG-2, MPEG-2.5 adds new sampling rates exactly half of that previously possible with MPEG-2. It thus widens the scope of MP3 to include human speech and other applications requiring only 25% of the frequency reproduction possible with MPEG-1. While not an ISO recognized standard, MPEG-2.5 is widely supported by both inexpensive and brand name digital audio players as well as computer software based MP3 encoders and decoders. A sample rate comparison between MPEG-1, 2 and 2.5 is given further down. MPEG-2.5 was not developed by MPEG and was never approved as an international standard. MPEG-2.5 is thus an unofficial or proprietary extension to the MP3 format.

qas: question: What defines the compression efficiency of encoders?
answers: text: bit rate

question: Compression ratio depends on the sample rate and bit depth of which signal?
answers: text: input

question: What does CD stand for?
answers: text: Compact Disc

question: What can CD parameters be used as references for?
answers: text: compression ratios

question: Other than CD parameters, what else can be used as parameter references?
answers: text: Digital Audio Tape (DAT) SP
context: Compression efficiency of encoders is typically defined by the bit rate, because compression ratio depends on the bit depth and sampling rate of the input signal. Nevertheless, compression ratios are often published. They may use the Compact Disc (CD) parameters as references (44.1 kHz, 2 channels at 16 bits per channel or 2×16 bit), or sometimes the Digital Audio Tape (DAT) SP parameters (48 kHz, 2×16 bit). Compression ratios with this latter reference are higher, which demonstrates the problem with use of the term compression ratio for lossy encoders.

qas: question: What type of recording did Brandenburg use?
answers: text: CD

question: What did Brandenburg use the recording to refine?
answers: text: the MP3 compression algorithm

question: What word describes the nature of the song used?
answers: text: monophonic

question: As a result of her song being used, Suzanne Vega is sometimes referred to as what?
answers: text: The mother of MP3

question: Excerpts were taken from which reference compact disc to assess the subjective quality of the MPEG audio formats?
answers: text: EBU V3/SQAM
context: Karlheinz Brandenburg used a CD recording of Suzanne Vega's song "Tom's Diner" to assess and refine the MP3 compression algorithm. This song was chosen because of its nearly monophonic nature and wide spectral content, making it easier to hear imperfections in the compression format during playbacks. Some refer to Suzanne Vega as "The mother of MP3". This particular track has an interesting property in that the two channels are almost, but not completely, the same, leading to a case where Binaural Masking Level Depression causes spatial unmasking of noise artifacts unless the encoder properly recognizes the situation and applies corrections similar to those detailed in the MPEG-2 AAC psychoacoustic model. Some more critical audio excerpts (glockenspiel, triangle, accordion, etc.) were taken from the EBU V3/SQAM reference compact disc and have been used by professional sound engineers to assess the subjective quality of the MPEG Audio formats.

qas: question: Which language was the reference simulation software written in?
answers: text: C

question: Who developed the reference simulation software?
answers: text: the ISO MPEG Audio committee

question: When was the reference software approved?
answers: text: March 1994

question: When did the reference software become an international standard?
answers: text: 1998

question: What could the reference software demonstrate?
answers: text: real time hardware decoding
context: A reference simulation software implementation, written in the C language and later known as ISO 11172-5, was developed (in 1991–1996) by the members of the ISO MPEG Audio committee in order to produce bit compliant MPEG Audio files (Layer 1, Layer 2, Layer 3). It was approved as a committee draft of ISO/IEC technical report in March 1994 and printed as document CD 11172-5 in April 1994. It was approved as a draft technical report (DTR/DIS) in November 1994, finalized in 1996 and published as international standard ISO/IEC TR 11172-5:1998 in 1998. The reference software in C language was later published as a freely available ISO standard. 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.

qas: question: When was the first software MP3 encoder released?
answers: text: 7 July 1994

question: What was the name of the first software MP3 encoder?
answers: text: l3enc

question: What was the filename extension?
answers: text: .mp3

question: What was the name of the first real-time software MP3 player?
answers: text: WinPlay3

question: What was the average high end hard drive size?
answers: text: 1000 MB
context: On 7 July 1994, the Fraunhofer Society released the first software MP3 encoder called l3enc. The filename extension .mp3 was chosen by the Fraunhofer team on 14 July 1995 (previously, the files had been named .bit). With the first real-time software MP3 player WinPlay3 (released 9 September 1995) many people were able to encode and play back MP3 files on their PCs. Because of the relatively small hard drives back in that time (~ 500–1000 MB) lossy compression was essential to store non-instrument based (see tracker and MIDI) music for playback on computer.

qas: question: What was Jonathan Sterne's profession?
answers: text: sound scholar

question: Which nationality was the hacker who acquired I3enc?
answers: text: Australian

question: What did the hacker use to acquire the software?
answers: text: stolen credit card

question: The hacker re-wrote which element of the program?
answers: text: user interface

question: How much did the new released program by the hacker cost?
answers: text: free
context: As sound scholar Jonathan Sterne notes, "An Australian hacker acquired l3enc using a stolen credit card. The hacker then reverse-engineered the software, wrote a new user interface, and redistributed it for free, naming it "thank you Fraunhofer"".

qas: question: Where did MP3s begin to spread?
answers: text: the Internet

question: Which audio player was released in 1997?
answers: text: Winamp

question: Who released the audio player?
answers: text: Nullsoft

question: What was the name of the first portable solid state digital audio player?
answers: text: MPMan

question: In which country was the first portable audio player developed?
answers: text: South Korea
context: In the second half of '90s, MP3 files began to spread on the Internet. The popularity of MP3s began to rise rapidly with the advent of Nullsoft's audio player Winamp, released in 1997. In 1998, the first portable solid state digital audio player MPMan, developed by SaeHan Information Systems which is headquartered in Seoul, South Korea, was released and the Rio PMP300 was sold afterwards in 1998, despite legal suppression efforts by the RIAA.

qas: question: Which website offered MP3s for free?
answers: text: mp3.com

question: How many MP3s were offered for free by the website?
answers: text: thousands

question: What kind of file sharing became popular due to the file sizes of MP3s?
answers: text: peer-to-peer

question: How did people come into possession of MP3s?
answers: text: ripped from CDs

question: Which network was the first large peer to peer file sharing network?
answers: text: Napster
context: In November 1997, the website mp3.com was offering thousands of MP3s created by independent artists for free. The small size of MP3 files enabled widespread peer-to-peer file sharing of music ripped from CDs, which would have previously been nearly impossible. The first large peer-to-peer filesharing network, Napster, was launched in 1999.

qas: question: What kind of infringement resulted from sharing MP3s?
answers: text: copyright

question: What name did the record companies associate with MP3 file sharing?
answers: text: music piracy

question: Who was the target of the record companies?
answers: text: Napster

question: What happened to Napster?
answers: text: shut down and later sold
context: The ease of creating and sharing MP3s resulted in widespread copyright infringement. Major record companies argued that this free sharing of music reduced sales, and called it "music piracy". They reacted by pursuing lawsuits against Napster (which was eventually shut down and later sold) and against individual users who engaged in file sharing.

qas: question: What kind of MP3 file sharing continues on?
answers: text: Unauthorized

question: Beatport, Bleep and Juno records are examples of what kind of service?
answers: text: authorized

question: What kind of music is sold by these companies?
answers: text: unrestricted

question: Which format is used by the companies that sell the music legally?
answers: text: MP3
context: Unauthorized MP3 file sharing continues on next-generation peer-to-peer networks. Some authorized services, such as Beatport, Bleep, Juno Records, eMusic, Zune Marketplace, Walmart.com, Rhapsody, the recording industry approved re-incarnation of Napster, and Amazon.com sell unrestricted music in the MP3 format.

qas: question: A header and data block together make up what?
answers: text: MP3 frames

question: What is a sequence of MP3 frames called?
answers: text: elementary stream

question: What is used to identify the begining of a valid frame of an MP3 header?
answers: text: dard

question: How many bits are needed to indicate that layer 3 is used?
answers: text: two

question: MP3 files today contain what kind of metadeta?
answers: text: ID3
context: An MP3 file is made up of MP3 frames, which consist of a header and a data block. This sequence of frames is called an elementary stream. Due to the "byte reservoir", frames are not independent items and cannot usually be extracted on arbitrary frame boundaries. The MP3 Data blocks contain the (compressed) audio information in terms of frequencies and amplitudes. The diagram shows that the MP3 Header consists of a sync word, which is used to identify the beginning of a valid frame. This is followed by a bit indicating that this is the MPEG standard and two bits that indicate that layer 3 is used; hence MPEG-1 Audio Layer 3 or MP3. After this, the values will differ, depending on the MP3 file. ISO/IEC 11172-3 defines the range of values for each section of the header along with the specification of the header. Most MP3 files today contain ID3 metadata, which precedes or follows the MP3 frames, as noted in the diagram.

qas: question: Which standard does not include a specification for an MP3 encoder?
answers: text: MPEG-1

question: Example psychoacoustic models and rate loops can be foundin which part of the original standard?
answers: text: non-normative

question: What were implementers of the standard supposed to devise?
answers: text: their own algorithms

question: It is easy for a prospective user of an encoder to research the best choice because of what factor?
answers: text: Comparisons are widely available

question: An encoder that is proficient at encoding at higher bit rates might be worse at what?
answers: text: lower bit rates
context: The MPEG-1 standard does not include a precise specification for an MP3 encoder, but does provide example psychoacoustic models, rate loop, and the like in the non-normative part of the original standard. At present, these suggested implementations are quite dated. Implementers of the standard were supposed to devise their own algorithms suitable for removing parts of the information from the audio input. As a result, there are many different MP3 encoders available, each producing files of differing quality. Comparisons are widely available, so it is easy for a prospective user of an encoder to research the best choice. An encoder that is proficient at encoding at higher bit rates (such as LAME) is not necessarily as good at lower bit rates.

qas: question: How many domain samples are taken during encoding?
answers: text: 576

question: Domain samples are transformed into what?
answers: text: frequency-domain samples

question: When are 192 samples taken instead of 576?
answers: text: there is a transient

question: When 192 samples are taken instead of 576, it is done in an effort to limit what?
answers: text: temporal spread

question: What accompanies a transient?
answers: text: quantization noise
context: During encoding, 576 time-domain samples are taken and are transformed to 576 frequency-domain samples.[clarification needed] If there is a transient, 192 samples are taken instead of 576. This is done to limit the temporal spread of quantization noise accompanying the transient. (See psychoacoustics.)

qas: question: What kind of structure does a filter bank have?
answers: text: tree

question: Due to a specific kind of structure, what kind of problems are made worse?
answers: text: pre-echo problems

question: What kind of resolution are the filter banks unable to provide an optimal solution for?
answers: text: time/frequency

question: Combining two filter banks' outputs creates what kind of problem?
answers: text: aliasing

question: The need to code excess energy in the frequency domain decreases what kind of efficiency?
answers: text: coding
context: Due to the tree structure of the filter bank, pre-echo problems are made worse, as the combined impulse response of the two filter banks does not, and cannot, provide an optimum solution in time/frequency resolution. Additionally, the combining of the two filter banks' outputs creates aliasing problems that must be handled partially by the "aliasing compensation" stage; however, that creates excess energy to be coded in the frequency domain, thereby decreasing coding efficiency.[citation needed]

qas: question: What is carefully defined in the standard?
answers: text: Decoding

question: What are most decoders?
answers: text: bitstream compliant

question: The ISO/IEC high standard document states that the decompressed output produced from a given MP3 file will be the same within what standards?
answers: text: specified degree of rounding tolerance

question: Decoders are usually compared by examining which factor?
answers: text: computationally efficient

question: The efficiency of decoders is examined by seeing how much memory and what other process they use in the decoding process?
answers: text: CPU time
context: Decoding, on the other hand, is carefully defined in the standard. Most decoders are "bitstream compliant", which means that the decompressed output that they produce from a given MP3 file will be the same, within a specified degree of rounding tolerance, as the output specified mathematically in the ISO/IEC high standard document (ISO/IEC 11172-3). Therefore, comparison of decoders is usually based on how computationally efficient they are (i.e., how much memory or CPU time they use in the decoding process).

qas: question: What is there no official provision for?
answers: text: gapless playback

question: What is an example of an encoder that can attach additional metadeta?
answers: text: LAME

question: Adding additional metadata allows players to handle gapless playback and deliver what?
answers: text: seamless playback

question: For encoders and decoders, what is not defined?
answers: text: overall delay
context: Encoder / decoder overall delay is not defined, which means there is no official provision for gapless playback. However, some encoders such as LAME can attach additional metadata that will allow players that can handle it to deliver seamless playback.

qas: question: A typical trade off when creating an MP3 file is between the amount of space used and what other factor?
answers: text: sound quality of the result

question: What would an example of lossy audio encoding be?
answers: text: creating an MP3 file

question: Who gets to set the bit rate for an MP3 file?
answers: text: the creator

question: What does the bit rate of the file actually mean?
answers: text: how many kilobits the file may use per second of audio

question: If the bit rate is higher, the size of the compressed file will be what?
answers: text: larger
context: When performing lossy audio encoding, such as 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 is allowed to set a bit rate, which specifies how many kilobits the file may use per second of audio. The higher the bit rate, the larger the compressed file will be, and, generally, the closer it will sound to the original file.

qas: question: If the bit rate is too low, what might be audible in the reproduction?
answers: text: compression artifacts

question: Sounds that were not in the original recording are referred to as what?
answers: text: compression artifacts

question: Randomness and sharp attacks are two reasons that may make it harder to to do what to an audio file?
answers: text: compress

question: Other than pre - echo, what is another example of what can happen when audio is compressed?
answers: text: ringing

question: What kind of sample can display a good example of compression artifacts?
answers: text: A sample of applause
context: 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 low bit rate provides a good example of compression artifacts.

qas: question: Other than the bit rate and the difficulty of the signal, what can also affect the quality of an MP3 file?
answers: text: quality of the encoder

question: The MP3 standard allows encoders to have a lot of freedom with which aspect of encoding?
answers: text: encoding algorithms

question: As a result of the freedom, different encoders can result in different quality even if which aspect of the file is the same?
answers: text: bit rates

question: An example shown has a low range quality score of what value?
answers: text: 2.22

question: To compare qualities, sound files are evaluated on a scale that ranges from 1 to what?
answers: text: 5
context: 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 with identical bit rates. As an example, in a public listening test featuring two different MP3 encoders at about 128 kbit/s, one scored 3.66 on a 1–5 scale, while the other scored only 2.22.

qas: question: How many bit rates does the simplest type of MP3 file use?
answers: text: one

question: What does CBR stand for?
answers: text: Constant Bit Rate

question: What does VBR stand for?
answers: text: Variable Bit Rate

question: Aside from silence, which sections of music highlight parts that are easier to compress?
answers: text: music containing only a few instruments

question: What value do users need to know when encoding their music to help avoid them having to do tests on each piece of music?
answers: text: quality setting
context: The simplest type of MP3 file uses one bit rate for the entire file: this is known as Constant Bit Rate (CBR) encoding. Using a constant bit rate makes encoding simpler and faster. However, it is also possible to create files where the bit rate changes throughout the file. These are known as Variable Bit Rate (VBR) files. The idea behind this is that, in any piece of audio, some parts will be much easier to compress, such as silence or music containing only a few instruments, while others will be more difficult to compress. So, the overall quality of the file may be increased by using a lower bit rate for the less complex passages and a higher one for the more complex parts. With some encoders, it is possible to specify a given quality, and the encoder will vary the bit rate accordingly. Users who know a particular "quality setting" that is transparent to their ears can use this value when encoding all of their music, and generally speaking not need to worry about performing personal listening tests on each piece of music to determine the correct bit rate.

qas: question: A listening environment is also know by which term?
answers: text: ambient noise

question: Other than speakers and headphones, what other piece of equipment affects the listener's perceived quality?
answers: text: sound cards

question: Listening environment, listener attention, listener training and listener audio equipment can all affect what kind of quality?
answers: text: Perceived quality
context: Perceived quality can be influenced by listening environment (ambient noise), listener attention, and listener training and in most cases by listener audio equipment (such as sound cards, speakers and headphones).

qas: question: Who gave students a test to determine their preferences?
answers: text: Music Professor Jonathan Berger

question: Where was a test performed to collect data on student preference for MP3 quality?
answers: text: Stanford University

question: Data showed that students' preference for MP3 quality music followed which trend?
answers: text: risen each year

question: What kind of sound did students seem to prefer?
answers: text: sizzle
context: A test given to new students by Stanford University Music Professor Jonathan Berger showed that student preference for MP3-quality music has risen each year. Berger said the students seem to prefer the 'sizzle' sounds that MP3s bring to music.

qas: question: What is the name of the study done by composer Ryan Maguire?
answers: text: The Ghost in the MP3

question: What did the study aim to isolate?
answers: text: sounds lost during MP3 compression

question: What is the track "moDernisT" an anagram of?
answers: text: Tom's Diner

question: Where was an account of the study published?
answers: text: International Computer Music Conference

question: Which year was the study published?
answers: text: 2014
context: An in-depth study of MP3 audio quality, sound artist and composer Ryan Maguire's project "The Ghost in the MP3" isolates the sounds lost during MP3 compression. In 2015, he released the track "moDernisT" (an anagram of "Tom's Diner"), composed exclusively from the sounds deleted during MP3 compression of the song "Tom's Diner", the track originally used in the formulation of the MP3 standard. A detailed account of the techniques used to isolate the sounds deleted during MP3 compression, along with the conceptual motivation for the project, was published in the 2014 Proceedings of the International Computer Music Conference.

qas: question: What is the name of the sampling theorem?
answers: text: Nyquist–Shannon

question: In relation to the sampling frequency, the frequency reproduction is strictly how much less?
answers: text: less than half

question: What kind of filter requires a larger margin for error?
answers: text: imperfect filters

question: Having an 8 kHz sampling rate would limit the maximum frequency to how much?
answers: text: 4 kHz

question: A sound reproduction of 24 kHz would represent which value of a maximum sampling rate?
answers: text: 48
context: Several bit rates are specified in the MPEG-1 Audio Layer III standard: 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/s, with available sampling frequencies of 32, 44.1 and 48 kHz. MPEG-2 Audio Layer III allows bit rates of 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 kbit/s with sampling frequencies of 16, 22.05 and 24 kHz. MPEG-2.5 Audio Layer III is restricted to bit rates of 8, 16, 24, 32, 40, 48, 56 and 64 kbit/s with sampling frequencies of 8, 11.025, and 12 kHz.[citation needed] Because of the Nyquist–Shannon sampling theorem, frequency reproduction is always strictly less than half of the sampling frequency, and imperfect filters requires a larger margin for error (noise level versus sharpness of filter), so 8 kHz sampling rate limits the maximum frequency to 4 kHz, while 48 kHz maximum sampling rate limits an MP3 to 24 kHz sound reproduction.

qas: question: What sampling rate is used for CD audio?
answers: text: 44.1 kHz

question: What is the main source used for creating MP3 files?
answers: text: CD audio

question: Where can one find a greater variety of bit rates?
answers: text: the Internet

question: The common bit rate on the internet is 128 kbit/s using which compression ratio?
answers: text: 11:1

question: As technology advances, what is another higher bit rate that is beginning to spread?
answers: text: 320 kbit/s
context: A sample rate of 44.1 kHz is almost always used, because this is also used for CD audio, the main source used for creating MP3 files. A greater variety of bit rates are used on the Internet. The rate of 128 kbit/s is commonly used, at a compression ratio of 11:1, offering adequate audio quality in a relatively small space. As Internet bandwidth availability and hard drive sizes have increased, higher bit rates up to 320 kbit/s are widespread.

qas: question: What is stored on an audio-CD that has a bit rate of 1,411.2 kbit/s?
answers: text: Uncompressed audio

question: What does a bit rate of 128 represent in terms of compression ratio?
answers: text: 11:1

question: What would a bit rate of 160 correspond to in terms of compression ratio?
answers: text: 9:1

question: What would a bit rate of 192 kbit/s have for a compression ratio?
answers: text: 7:1
context: Uncompressed audio as stored on an audio-CD has a bit rate of 1,411.2 kbit/s, (16 bit/sample × 44100 samples/second × 2 channels / 1000 bits/kilobit), so the bitrates 128, 160 and 192 kbit/s represent compression ratios of approximately 11:1, 9:1 and 7:1 respectively.

qas: question: What is the highest bit rate the LAME encoder allows?
answers: text: 640 kbit/s

question: The LAME encoder allows bit rates that are what?
answers: text: Non-standard

question: Even though few MP3 players can play it, LAME also offers which option?
answers: text: freeformat

question: The ISO standard dictates that decoders only need to be able to decode streams that have how high of a bit rate?
answers: text: 320
context: Non-standard bit rates up to 640 kbit/s can be achieved with the LAME encoder and the freeformat option, although few MP3 players can play those files. According to the ISO standard, decoders are only required to be able to decode streams up to 320 kbit/s.

qas: question: What does the term CBR mean?
answers: text: Constant Bit Rate

question: Which early MPEG layer used CBR?
answers: text: Layer III

question: The early software was restricted to which kind of bitrate?
answers: text: uniform

question: What did more sophisticated MP3 encoders use to target an average bit rate?
answers: text: bit reservoir

question: What did encoders base the encoding rate for each frame on?
answers: text: the complexity of the sound
context: Early MPEG Layer III encoders used what is now called Constant Bit Rate (CBR). The software was only able to use a uniform bitrate on all frames in an MP3 file. Later more sophisticated MP3 encoders were able to use the bit reservoir to target an average bit rate selecting the encoding rate for each frame based on the complexity of the sound in that portion of the recording.

qas: question: What kind of audio can a sophisticated MP3 encoder produce?
answers: text: variable bitrate audio

question: Which type of decoder must support bitrate switching on a per-frame basis?
answers: text: layer III

question: What do encoders use when the goal is to achieve a fixed level of quality?
answers: text: VBR

question: Using VBR instead of a constant bit rate encoding makes which part of encoding less predictable?
answers: text: final file size

question: An average bit rate is used when who choses an average value for the encoder to use?
answers: text: the user
context: A more sophisticated MP3 encoder can produce variable bitrate audio. MPEG audio may use bitrate switching on a per-frame basis, but only layer III decoders must support it. VBR is used when the goal is to achieve a fixed level of quality. The final file size of a VBR encoding is less predictable than with constant bitrate. Average bitrate is VBR implemented as a compromise between the two: the bitrate is allowed to vary for more consistent quality, but is controlled to remain near an average value chosen by the user, for predictable file sizes. Although an MP3 decoder must support VBR to be standards compliant, historically some decoders have bugs with VBR decoding, particularly before VBR encoders became widespread.

qas: question: A partially full frame's ability to have part of the next frame's audio data is referred to as what?
answers: text: bit reservoir

question: What kind of audio is required to use a bit reservoir?
answers: text: Layer III

question: A bit reservoir allows for what kind of changes in effective bit rate?
answers: text: temporary

question: What is a possible result of handling the bit reservoir?
answers: text: encoding delay

question: A large benefit of a bit reservoir is that you can use it even while encoding what kind of stream?
answers: text: constant bitrate
context: Layer III audio can also use a "bit reservoir", a partially full frame's ability to hold part of the next frame's audio data, allowing temporary changes in effective bitrate, even in a constant bitrate stream. Internal handling of the bit reservoir increases encoding delay.[citation needed]

qas: question: What can scale factor band 21 be shortened to?
answers: text: sfb21

question: What is the maximum frequency that scale factor band 21 can go up to?
answers: text: 16 kHz

question: The encoder has to choose between less acurate representation in band 21 or which factor in all bands below band 21?
answers: text: less efficient storage

question: What does less efficient storage result in for VBR encoding?
answers: text: wasted bitrate
context: There is no scale factor band 21 (sfb21) for frequencies above approx 16 kHz, forcing the encoder to choose between less accurate representation in band 21 or less efficient storage in all bands below band 21, the latter resulting in wasted bitrate in VBR encoding.

qas: question: What is a section of a file that contains metadeta referred to as?
answers: text: tag

question: What else can metadeta contain other than the title, artist or track  number?
answers: text: album

question: What do MP3 standards not define?
answers: text: tag formats for MP3 files

question: What would be needed to support metadata and obviate the need for tags?
answers: text: a standard container format
context: A "tag" in an audio file is a section of the file that contains metadata such as the title, artist, album, track number or other information about the file's contents. The MP3 standards do not define tag formats for MP3 files, nor is there a standard container format that would support metadata and obviate the need for tags.

qas: question: Other than the ID3v1, which similar standard format for tag exists?
answers: text: ID3v2

question: What is the most recently introduced standard for tag formatting?
answers: text: APEv2

question: What is the second place in a file that tags are normally stored, with the first being at the beginning?
answers: text: end

question: What is important to note about where the tags are stored?
answers: text: separate from the actual MP3 frame data

question: If the MP3 decoders do not extract information from the tags, what do they do to them?
answers: text: treat them as ignorable, non-MP3 junk data
context: However, several de facto standards for tag formats exist. As of 2010, the most widespread are ID3v1 and ID3v2, and the more recently introduced APEv2. These tags are normally embedded at the beginning or end of MP3 files, separate from the actual MP3 frame data. MP3 decoders either extract information from the tags, or just treat them as ignorable, non-MP3 junk data.

qas: question: What is the name given to the standard for measure and storing the loudness of an MP3 file?
answers: text: ReplayGain

question: What is measuring and storing loudness of an MP3 file also known as?
answers: text: audio normalization

question: What does the standard ReplayGain allow a player to automatically adjust?
answers: text: the overall playback volume

question: What program can be used to modify files based on ReplayGain measurements?
answers: text: MP3Gain

question: MP3Gain is important because it allows players without what capability to have adjusted playback?
answers: text: ReplayGain capability
context: ReplayGain is a standard for measuring and storing the loudness of an MP3 file (audio normalization) in its metadata tag, enabling a ReplayGain-compliant player to automatically adjust the overall playback volume for each file. MP3Gain may be used to reversibly modify files based on ReplayGain measurements so that adjusted playback can be achieved on players without ReplayGain capability.

qas: question: Where is the basic MP3 decoding and technology patent free?
answers: text: European Union

question: What happened to the patents that caused them to be patent-free?
answers: text: expired

question: When will the technology be patent - free in the United States?
answers: text: 31 December 2017

question: Between which years did most of the MP3 patents in the US expire?
answers: text: 2007 and 2015
context: The basic MP3 decoding and encoding technology is patent-free in the European Union, all patents having expired there. In the United States, the technology will be substantially patent-free on 31 December 2017 (see below). The majority of MP3 patents expired in the US between 2007 and 2015.

qas: question: What has many organizations claiming ownership of patents related to aspects of MP3 led to?
answers: text: legal threats

question: Legal threats and confusion made it difficult to ensure what about patents regarding MP3 products?
answers: text: which patents must be licensed

question: What was the danger of not correctly patenting products?
answers: text: patent infringement

question: At what stage of the technology were these problems prevalent?
answers: text: early stages
context: In the past, many organizations have claimed ownership of patents related to MP3 decoding or encoding. These claims led to a number of legal threats and actions from a variety of sources. As a result, uncertainty about which patents must be licensed in order to create MP3 products without committing patent infringement in countries that allow software patents was a common feature of the early stages of adoption of the technology.

qas: question: What became publicly available on 6 December 1991?
answers: text: MPEG-1 standard

question: When can patents not be filed in most countries?
answers: text: after prior art has been made public

question: How long does it take for patents to expire after being filed?
answers: text: 20 years

question: How long can it take for patents to be approved after initially being filed?
answers: text: 12 months

question: When did patents required to implement MP3 expire in most countries?
answers: text: December 2012
context: The initial near-complete MPEG-1 standard (parts 1, 2 and 3) was publicly available on 6 December 1991 as ISO CD 11172. In most countries, patents cannot be filed after prior art has been made public, and patents expire 20 years after the initial filing date, which can be up to 12 months later for filings in other countries. As a result, patents required to implement MP3 expired in most countries by December 2012, 21 years after the publication of ISO CD 11172.

qas: question: How long does it take for patents to expire in the United States?
answers: text: 17 years after the publication date

question: A patent issue much later than normally expected can be referred to as what?
answers: text: submarine patents

question: What year is the latest that MP3 related patents will expire on in the United States?
answers: text: 2017

question: Who holds the longest running MP3 patent in the United States?
answers: text: Fraunhofer-Gesellschaft

question: Who administered the longest running MP3 patent in the United States?
answers: text: Technicolor
context: An exception is the United States, where patents filed prior to 8 June 1995 expire 17 years after the publication date of the patent, but application extensions make it possible for a patent to issue much later than normally expected (see submarine patents). The various MP3-related patents expire on dates ranging from 2007 to 2017 in the U.S. Patents filed for anything disclosed in ISO CD 11172 a year or more after its publication are questionable. If only the known MP3 patents filed by December 1992 are considered, then MP3 decoding has been patent-free in the US since 22 September 2015 when U.S. Patent 5,812,672 expired which had a PCT filing in October 1992. If the longest-running patent mentioned in the aforementioned references is taken as a measure, then the MP3 technology will be patent-free in the United States on 30 December 2017 when U.S. Patent 5,703,999, held by the Fraunhofer-Gesellschaft and administered by Technicolor, expires.

qas: question: What was Technicolor's previous name?
answers: text: Thomson Consumer Electronics

question: What patent does Technicolor claim to control?
answers: text: Layer 3

question: What are Technicolor constantly in the process of doing?
answers: text: actively enforcing these patents
context: Technicolor (formerly called Thomson Consumer Electronics) claims to control MP3 licensing of the Layer 3 patents in many countries, including the United States, Japan, Canada and EU countries. Technicolor has been actively enforcing these patents.

qas: question: When did the Fraunhofer institute send out a letter?
answers: text: September 1998

question: What did the letter claim would be required to distribute and/or sell decoders and/or encoders?
answers: text: a license

question: What does selling unlicensed products mean that the seller is doing?
answers: text: infringe the patent rights of Fraunhofer and Thomson

question: What can products not use if they want to avoid infringing on patent rights?
answers: text: the [MPEG Layer-3] standard
context: In September 1998, the Fraunhofer Institute sent a letter to several developers of MP3 software stating that a license was required to "distribute and/or sell decoders and/or encoders". The letter claimed that unlicensed products "infringe the patent rights of Fraunhofer and Thomson. To make, sell and/or distribute products using the [MPEG Layer-3] standard and thus our patents, you need to obtain a license under these patents from us."

qas: question: Who was sued for patent infringement on MP3 technology?
answers: text: Thomson

question: Who initially sued to protect their patent rights?
answers: text: Sisvel S.p.A.

question: What did Sisvel grant Thomson to end the lawsuit?
answers: text: a license to their patents

question: When did the majority of the patents held by Sisvel expire?
answers: text: 2015

question: When does the last patent held by Sisvel expire?
answers: text: 9. April 2017
context: Sisvel S.p.A. and its U.S. subsidiary Audio MPEG, Inc. previously sued Thomson for patent infringement on MP3 technology, but those disputes were resolved in November 2005 with Sisvel granting Thomson a license to their patents. Motorola followed soon after, and signed with Sisvel to license MP3-related patents in December 2005. Except for three patents, the US patents administered by Sisvel had all expired in 2015, however (the exceptions are: U.S. Patent 5,878,080, expires February 2017, U.S. Patent 5,850,456, expires February 2017 and U.S. Patent 5,960,037, expires 9. April 2017.

qas: question: What did German officials seize from SanDisk on September 2006?
answers: text: MP3 players

question: At which show did SanDisk have their assets seized?
answers: text: IFA

question: Which company was the Italian patents firm representing?
answers: text: Sisvel

question: What happened after the injunction was successful?
answers: text: The injunction was later reversed

question: The continuous back and forth regarding the decisions on patents was referred to as what?
answers: text: bringing the Patent Wild West to Germany
context: In September 2006, German officials seized MP3 players from SanDisk's booth at the IFA show in Berlin after an Italian patents firm won an injunction on behalf of Sisvel against SanDisk in a dispute over licensing rights. The injunction was later reversed by a Berlin judge, but that reversal was in turn blocked the same day by another judge from the same court, "bringing the Patent Wild West to Germany" in the words of one commentator.

qas: question: Who sued Apple, Samsung Electronics and Sandisk in 2007?
answers: text: Texas MP3 Technologies

question: Which court did the lawsuit take place in?
answers: text: eastern Texas federal court

question: What was the claim that the lawsuit was based on?
answers: text: infringement of a portable MP3 player patent

question: What action did the three companies being sued take?
answers: text: all settled the claims against them

question: What year did the lawsuits end?
answers: text: 2009
context: In February 2007, Texas MP3 Technologies sued Apple, Samsung Electronics and Sandisk in eastern Texas federal court, claiming infringement of a portable MP3 player patent that Texas MP3 said it had been assigned. Apple, Samsung, and Sandisk all settled the claims against them in January 2009.

qas: question: Which company allegedly inherited MP3 patents from AT&T-Bell LAbs?
answers: text: Alcatel-Lucent

question: What kind of patents were allegedly inherited?
answers: text: MP3 coding and compression

question: How many patents did Alcatel claim Microsoft infringed on?
answers: text: seven

question: How much money was awarded to Alcatel by a San Diego jury?
answers: text: US $1.52 billion

question: What subsequently happened after Alcatel was awarded damages?
answers: text: The court subsequently tossed the award
context: Alcatel-Lucent has asserted several MP3 coding and compression patents, allegedly inherited from AT&T-Bell Labs, in litigation of its own. In November 2006, before the companies' merger, Alcatel sued Microsoft for allegedly infringing seven patents. On 23 February 2007, a San Diego jury awarded Alcatel-Lucent US $1.52 billion in damages for infringement of two of them. The court subsequently tossed the award, however, finding that one patent had not been infringed and that the other was not even owned by Alcatel-Lucent; it was co-owned by AT&T and Fraunhofer, who had licensed it to Microsoft, the judge ruled. That defense judgment was upheld on appeal in 2008. See Alcatel-Lucent v. Microsoft for more information.

qas: question: AAC, mp3PRO and MP2 are all members of the same technological family as which other lossy format?
answers: text: MP3

question: What model type do all of the lossy formats roughly depend on?
answers: text: psychoacoustic

question: Which company owns many of the patents that cover the other formats?
answers: text: Fraunhofer Gesellschaft
context: Other lossy formats exist. Among these, mp3PRO, AAC, and MP2 are all members of the same technological family as MP3 and depend on roughly similar psychoacoustic models. The Fraunhofer Gesellschaft owns many of the basic patents underlying these formats as well, with others held by Dolby Labs, Sony, Thomson Consumer Electronics, and AT&T.

qas: question: Opus and Vorbis are two explans of what kind of compression format?
answers: text: open

question: Being open formats means that Opus and Vorbis can be used without what?
answers: text: any known patent restrictions

question: What are some benefits to some of the newer audio compression formats when compared to MP3?
answers: text: free of some limitations inherent to the MP3 format

question: How can one obtain an open compression format such as Opus or Vorbis?
answers: text: available free of charge
context: There are also open compression formats like Opus and Vorbis that are available free of charge and without any known patent restrictions. Some of the newer audio compression formats, such as AAC, WMA Pro and Vorbis, are free of some limitations inherent to the MP3 format that cannot be overcome by any MP3 encoder.

qas: question: What is a significant alternative to MP3?
answers: text: lossless formats

question: What can lossless formats provide?
answers: text: unaltered audio content

question: What is the downside of using a lossless format?
answers: text: increased file size

question: What is another example of a lossless format other than Apple Lossless?
answers: text: FLAC

question: What does FLAC stand for?
answers: text: Free Lossless Audio Codec
context: Besides lossy compression methods, lossless formats are a significant alternative to MP3 because they provide unaltered audio content, though with an increased file size compared to lossy compression. Lossless formats include FLAC (Free Lossless Audio Codec), Apple Lossless and many others.