Portable player for playing MP3 music (now compatible with wma, wav and other formats). Portable MP3 player was originally made by Korean Huang Guangzhu and Moon &; Hwang) was invented in 1997 and applied for related patents.
Detailed explanation of MP3 format technology development.
2.MP3 as a music format
MPEG- 1 Audio Layer 3, commonly called MP3, is a popular digital audio coding and lossy compression format. It aims to greatly reduce the amount of audio data, but for most users, the sound quality of playback has not decreased significantly compared with the original uncompressed audio. It was invented and standardized in 199 1 by a group of engineers from Fraunhofer-Gesellschaft in Hellem.
MPEG- 1 Audio Layer 3, commonly called MP3, is a popular digital audio coding and lossy compression format. It aims to greatly reduce the amount of audio data, but for most users, the sound quality of playback has not decreased significantly compared with the original uncompressed audio. It was invented and standardized in 199 1 by a group of engineers from Fraunhofer-Gesellschaft in Hellem.
General inspection
MP3 is a data compression format. It discards the data that is not important to human hearing in PCM audio data (similar to JPEG, which is a lossy image compression), thus achieving a smaller file size.
Many techniques are used in MP3, including psychoacoustics, to determine which part of audio can be discarded. MP3 audio can be compressed at different bit rates, which provides a series of compromises between data size and sound quality.
MP3 format uses hybrid conversion mechanism to convert time domain signal into frequency domain signal;
* 32-band polyphase integral filter (PQF)
* 36 or 12 tap modified discrete cosine filter (MDCT); The size of each subband can be 0... 1 and 2...3 1.
* Post-processing of aliasing attenuation
According to the MPEG specification, AAC (Advanced Audio Coding) in MPEG-4 will be the next generation MP3 format, although there are many important efforts to create and popularize other formats. However, due to the unprecedented popularity of MP3, the success of any other format is unlikely at present. MP3 has not only extensive client software support, but also many hardware support, such as portable media player (MP3 player) DVD and CD player.
develop
MPEG- 1 Audio Layer 2 coding was originally a digital audio broadcasting (DAB) project, which was managed by Egon Meier-Engelen of Deutsche Fors Chungs-und verschuanstalt fü r Luft-und Raum Fahrt (later called Deutsche Zentrum fü r Luft-und Raum Fahrt, German Aerospace Center). This project is a Eureka research project funded by the European Union, and its name is usually called EU- 147. The study period of EU- 147 is 1987 to 1994.
By 199 1 year, two proposals appeared: Musicam (called Layer 2) and ASPEC (Adaptive Spectrum Sensing Entropy Coding). Musicam method proposed by Philips in the Netherlands, CCETT in France and Institut für Rundfunktechnik in Germany is chosen because of its simplicity, robustness when errors occur and less computation when high-quality compression is performed. Musicam format based on subband coding is the key factor to determine MPEG audio compression format (sampling rate, frame structure, data header, sampling point per frame). This technology and its design idea are fully integrated into the definition of ISO MPEG audio Layer I, II and later Layer III(MP3) format. Under the auspices of Professor Musmann (Hanover University), the formulation of standards was completed by Leon van de Kerkhof (first floor) and Gerhard Stoll (second floor).
Leon van der Kerkhof of the Netherlands, Gerhard Stoll of Germany, Yves Fran of France? The working group composed of German ois Dehery and Karlheinz Brandenburg absorbed the design ideas of Musicam and ASPEC, and added their own design ideas to develop MP3, which can reach the sound quality of MP2 192kbit/s at128kbit/s. ..
All these algorithms eventually became part of the first standard group of 1992 MPEG- 1, and the international standard ISO/IEC1172-3 published in 1993 was produced. Further work on MPEG audio eventually became a part of the second MPEG standard group MPEG-2, which was formulated in 1994. The official name of this standard is ISO/IEC 138 18-3, which was first published in 0995.
The compression efficiency of an encoder is usually defined by the bit rate, because the compression rate depends on the number of bits (:en: bit depth) and the sampling rate of the input signal. However, some products often use CD parameters (44. 1kHz, two channels, each channel with 16 bit or 2x 16 bit) as the compression ratio reference, and the compression ratio using this reference is usually high, which also explains the compression ratio problem of lossy compression.
Karlheinz Brandenburg used Suzanne Vega's song Tom's Dinner on CD media to evaluate MP3 compression algorithm. This song is used because its soft and simple melody makes it easier for people to hear the defects of compressed format when playing back. Some people call Suzanne Vega "the mother of MP3". More serious and critical audio excerpts (Zhong Qin, grand piano, accordion, ...) are used by professional audio engineers to evaluate the subjective quality of MPEG audio formats.
MP3 goes to the public.
In order to generate bit-compatible MPEG audio files (1 layer, 2-layer and 3-layer), members of ISO MPEG Audio Committee developed a reference simulation software named ISO 1 172-5 in C language. On some non-real-time operating systems, the first real-time hardware decoding of compressed audio based on DSP can be demonstrated. Some other MPEG audio is developed in real time for digital broadcasting (radio DAB and television DVB) of consumer receivers and set-top boxes.
Later, on July 7th, 1994,/kloc-0, Fraunhofer-Gesellschaft released the first MP3 encoder named l3enc.
The Fraunhofer development team chose the extension .mp3 (formerly. Bit) July 1995. Many people can encode and play back MP3 files on personal computers with the first real-time software WinPlay 3 (65438+ released on September 9th, 0995). Because the hard disk at that time was relatively small (for example, 500MB), this technology was very important for storing entertainment music on the computer.
MP2, MP3 and Internet
1June 1993, (MPEG- 1 audio layer 2) files appeared on the internet, which were often played by MPEG audio players. Later, MAPlay developed by Tobias Bading for Unix appeared. MAPlay was first released in/kloc-0 on February 22nd, 1999, and now it has been ported to Microsoft Windows platform.
At first, the only MP2 encoder products were Xing Encoder and CDDA2WAV, which are CD grabbers that convert CD tracks into WAV format.
The Internet Underground Music Archives (IUMA) is generally regarded as the originator of the online music revolution. IUMA is the first hi-fi music website on the Internet. Before the popularity of MP3 and Internet, it had thousands of MP2 licensed records.
From the first half of 1995 to the end of 1990s, MP3 began to flourish on the Internet. The popularity of MP3 is mainly due to the success of Winamp released by Nullsoft in 1997 and Napster released by Napster in 1999, which promote each other's development. These programs make it easy for ordinary users to play, make, enjoy and collect MP3 files.
In recent years, the debate about file sharing of MP3 file peer-to-peer technology has spread rapidly-mainly because compression makes file sharing possible, while uncompressed files are too large to share. Because MP3 files are widely spread through the Internet, some major record manufacturers have sued Napster to protect their copyright (see Intellectual Property).
Commercial online music distribution services such as iTunes Music Store usually choose other or proprietary music file formats that support digital rights management (DRM) to control and restrict the use of digital music. DRM-supported formats are used to prevent copyright materials from being infringed, but most protection mechanisms can be cracked by some methods. Computer experts can use these methods to generate unlocked files that can be copied freely. A notable exception is Microsoft's Windows Media Audio 10 format, which has not been cracked yet. If you want to get a compressed audio file, the recorded audio stream must be compressed and the sound quality will be reduced.