Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Digital media audio The music industry has long been defined by its recording media from the earliest days of recorded sound the emphasis has been on the medium used to store the sound, from cylinders and paper tape up to digital versatile discs (DVDs). it is entirely feasible that music fans own multiple copies of their favorite recording, on different media — eight-track tape, cassette tape, 33 1/3 rpm album, maybe a 45 rpm single, compact disc, and now on DVD. The remarkable improvement in the processing power of computers, and the vast increase in computer storage capacity, combined with innovations in software that allowed digital recording and signal processing, these factors together began to have an impact on the music industry. The result was that high-quality digital recording could be done in a basement, on affordable equipment, at a standard that approached or equaled commercial quality recordings. the music could be distributed in the same media formats, even on compact discs, pressed at home, “on demand”. New artists could begin to record and market their own music. The historical control that labels held over recording deals had been weakened, but the barriers to reaching a wider audience remained. Getting airplay on the radio and shelf space in the stores remained as obstacles to getting music into the hands of fans. the Internet provides an opportunity for artists to reach out directly to the consumers, and to do so in a way that integrated the numerous segmented markets around the country, indeed, around the world. The potential and problems of digital audio file distribution have been known for years. Researchers have developed interesting mechanisms that actually do impose controls on the distribution of files and the means by which they can be played; AT&T developed a system during the dot com boom called A2B Music that embodied the concept, but it fared poorly in the market and ultimately faded away. Strategies such as the A2B Music approach work well at a prototype level, but have never been successful in the commercial market. Two obstacles in particular have hindered success. The first is that the music companies have been reluctant to license their materials; even Napster approached companies early in their history in an attempt to license content, but were rebuffed. The second obstacle has been the reluctance of web users to “buy into” a proprietary system that effectively closes down all the advantages that they have come to associate with peer-topeer file sharing—it is a difficult marketing challenge to convince users to pay to use a very restricted system when they have had the experience of swapping for free. How would a controlled distribution system work? The concept utilizes a proprietary media player, with a specific embedded ID number. When the user chooses to download a music file, the file contains a digital license that is unique to that copy of the song, and specific to the individual user’s media player. The digital license determines the level of rights the user has purchased. For example, the license would allow a song to be played once, or ten times, or indefinitely, or it could be without restriction and thus eligible for free swapping. In this way, the music company could control marketing and promotions—giving away a swappable single, for example, to gain market awareness, or allowing any song to be downloaded and played one time, to see if the user likes it, then requiring a better license to be able to play it subsequently. If a user swapped a digitally licensed song on to a friend, the friend’s player would read the digital license embedded in the song file, and determine whether it was allowed to play the song or not. The combination of digital licenses and uniquely identified media players would effectively end the unauthorized swapping of controlled media files--at least until a hacker found a way to break the coding! One strategy to popularize the approach would be to allow free downloads of the player, and provide a steady stream of free content to help popularize the player. New releases from big artists might get an advance release through the proprietary system, thus encouraging avid fans to hear the song first through the system. In this way, a critical mass of installed players could then help launch a commercial system. Users could choose a song from the catalogue or a playlist, and if their license needed upgrading, they could “click to play” and agree to pay a small fee (charged to their accounts) to acquire the right level of digital license. If designed properly, it is conceivable that everyone would be happy. Copyright would be protected. Creative marketing would be possible. Artists could see auditable figures and get their fair share of proceeds. . Users would get enormous content and, given the volume, likely at a very small fee per play, especially since the high costs associated with the manufacturing, distributing, and warehousing of the physical media would disappear. Such a scheme is technically feasible, and commercially viable, and something along these lines will emerge in the marketplace. Thus, the web could become the world’s largest jukebox, but at a penny or a nickel per play! How are digital music files created in the first place? How does the sound that comes from an instrument, which is really an analog wave form moving through the air, get saved as a digital file that we can play on a stereo, computer or a portable player? The analog wave form must be converted into an (arguably) equivalent digital form through the use of “sampling”. The original analog wave signal is measured or “sampled” at regular intervals and the measurement is stored as a 16-bit number. The sampling rate is a big part of what determines the audio quality, as more frequent sampling generates more data points, and more data points translate into better quality of the stored signal. The usual reference point for the quality of a digital audio recording is that used on a compact disc. On a CD, the music is sampled at a rate of 44,100 times per second (44.1 kHz), or roughly twice the audio bandwidth. This means that with 16 bits used for each sample, recording two channels (for stereo) of music for one second requires more than 1.4 megabits of storage. the very high sampling rate allows the sound on a CD to be essentially indistinguishable from the original live version for most people. the sound file can get pretty big: an average three-and-a-half-minute song will take up 294 megabits, or 36.75 megabytes, of storage space. A typical CD can store about 74 minutes of music, with a total storage capacity of roughly 784 megabytes. Most files on the web are measured in kilobytes, so a single CD-quality song is substantially bigger than an average web page, and will take considerably longer to download, on the scale of hours over a 56 kb modem. In order to make downloading music on-line even remotely feasible for the average person on the web, something had to be done to make those CD files smaller, but without completely losing the original quality of the CD recording. That something, as it turns out, was the MP3 file format. So where does the name MP3 come from? The specification for digital audio files is called MPEG, from the Moving Picture Experts Group (the guys that created the standard). The MPEG group established a family of standards designed to efficiently store moving pictures and audio in a highly compressed digital format. The MPEG-2 specification[1] includes three audio layers, with varying levels of audio compression. [1] “Generic Coding of Moving Pictures and Associated Audio”, International Standard IS13818 Layer 1 provides compression by a factor of 4, Layer 2 by a factor of about 6, while Layer 3 enables compression by a factor of about 10. The MPEG specifications are fairly technical but quite interesting; those curious are encouraged to investigate the details via the further reading section below. Thus, using MPEG-2, Audio Layer 3, or MP3 for short, a song can be compressed substantially and still retain the original CD quality sound. How is this possible? The short answer is that sounds outside of human hearing range are removed, and the remaining sound is compressed in a manner similar to typical file compression techniques. The MP3 specification is an “open standard”, which means that no one company or individual owns the standard. Therefore, support for MP3 is easy to incorporate into media environments as there are no licensing fees required. … napster! … The premise behind the creation of Napster was simple: create an easy way for people to swap MP3 format music files via the Internet. Shawn Fanning devised a strategy to do just that, and in spring of 1999 left college at Northeastern University to create the company that became known as Napster. The strategy was fairly simple: use the concept of peer-to-peer computing to allow users to share files with each other. In this way, the files are never actually stored on the Napster file servers, just the list of users and the files that they are willing to share. Napster quickly became one of the most accessed sites on the web, as an entire generation of young people (with highbandwidth university students leading the way) tuned in to the phenomenon. Napster effectively bypassed the established patterns of the music industry, which proved to be its strength and, ultimately, its weakness The traditional titans of the music industry soon focused on Napster as the very embodiment of the threats posed by the Internet to the music business, or, at least, their control of the industry. Napster did not include any sort of mechanisms for copyright protection or digital rights management, and this oversight became a rather troublesome problem, as the Recording Industry Association of America sued the service for copyright infringement … … and the band Metallica famously sued, and some recording artists also began to recognize the threat of unfettered copying of files. The legal entanglements brought an end to Napster in its original form. There are plans for the reemergence of the service, with a scheme for royalty payments for copyrighted materials, but the prospects do not seem promising. Meanwhile, there are tens of millions of former Napster users hungry for similar file-sharing and music-swapping services. The demand was met quickly by a new generation of peerto-peer file sharing systems, such as Gnutella and Kazaa. File swapping is still ongoing, and growing. It is interesting to note that the original design of Napster, wherein a list of users and their songlists was maintained in a central site, made it relatively easy to shut down. This design weakness was duly noted by other peer-to-peer systems, whose design now is more truly distributed with no central point of control, such that it would be quite difficult to shut the new services down. What Napster accomplished was to effectively create the world’s biggest jukebox, and provide a vivid demonstration that a new way of doing business was not only possible but, from the user’s point of view, far preferable. The technical capacity to swap files provided the “killer application” that developers have been seeking for years, one that took full advantage of the Internet paradigm and completely transformed the old way of doing business. an increasingly popular marketing tactic is to for web sites to promote artists and products by giving away selected audio tracks in the MP3 format as a way to draw customers to the site and (ideally) purchase the full compact disc and related products. Recall that in the case of downloading an MP3 file, the file is selected and then completely transferred and stored locally on the user’s machine before it can be played. There is a non-trivial delay between the request for the song and the first time that it can be played, as the file must be completely downloaded before play begins. The file remains locally stored, and thus does not require a return trip to the original web site to get another copy. Users effectively possess the copy, and can play it independently of the original server, or swap it with their friends. In the case of streaming media, the song is requested from the server and the transfer begins. The first portion of the song is buffered locally, in Random Access Memory, and starts playing before the entire transfer is complete The song is stored only in the buffer, temporarily, and is not saved onto the local disk. The significance is that streaming media files must be played from the source, every time, and can’t be saved or swapped by the user. If the users want to hear the song again, they must return to the original site and request it. A timeline of major events in the history of recorded music can be found at http://history.acusd.edu/gen/recording/notes.ht ml. A good starting point for MPEG facts and references can be found at http://www.mpeg.org. The music file sharing services mentioned can be found at: - Napster http://www.napster.com - Gnutella http://www.gnutella.com - Kazaa http://www.kazaa.com