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Ivan MikhaylukTheme of master's work:Analys and methods of protection of audio filesScientific supervisor: Gubenko Natlia Evgenievna |
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Presently the fight passes against the illegal reproducing of pieces of music. Thus at the use of mp3 of files the law is broken on copyrights on the piece of music. One of methods of decision this problem is the use of thread-marks confirmative authorship of work.
At introduction of aquatic mark it is necessary to take into account a file structure. The short structure of files of format of mp3 and WAV is presented below. Heading has length 32 beaten (4 bytes) and schematically represented on a picture 1. Every cage is 1 beaten.
 Picture 1. Structure of file mp3 Heading is begun with a certain element, urgent sync. He is used for synchronization and also for distinction of files of MP3 from other files. In obedience to the standard of MPEG sync consists of 12 set in succession bits. Some modifications of standard, created later use 11 set bats and one downfaulted.
Right after sync there is the bit of ID, which allows to distinguish MPEG-1 from MPEG-2. If 0 that, MPEG-2, if 1 that, MPEG-1 Following two bat determine the parameter of layer, that level into the standard of MPEG. Table 1
List of standards of file mp3. Field of bitrate jointly with certain before by the fields of ID and layer allows to define the stream of audiodata in kbt/sec
Frequency of discretization concernes from the field of frequency. Its value depends on what from the versions of standard of MPEG is used. In тегах ID3v1 and ID3v2 is kept references data about the name, performer, album, year of issue, comments to songs and genre. The name, performer, album and comment, is kept certificates in this теге as ASCII of code long a 30 byte, year - in long 4 bytes. A genre gets out from the array of genres long 0x00 . 147, at what numbers 148 - 254 reserved, and number 255 - is absent. The so-called are the main morphon of WAV-files element of chunks ("segment"). Chunk is begun with a three-plus-onecharacter identifier (for example 'RIFF', 'fmt ' or 'data'), a three-plus-onebyte number which it is writtenin in follows by him, how many bytes occupy this segment (eliminating the first eight bytes of heading), and his content is further disposed. On a picture 2 the structure of WAV-file format is presented.
 Picture 2. Structure of WAV-file format Segments can have quite different functional destiny, and it fully concernes the same by an identifier which a segment is begun with. A WAV-file structure is such on the whole. A file, from point of structure, also is a segment, named RIFF Chunk. To define RIFF-file character, an identifier is needed as, in this case it will be 'WAVE'. Further follow different family segments among which necessarily must be present Chunk (segment of format) Format with the identifier of 'fmt ' and Chunk (data segment) Data with the identifier of 'data'. The presence of other segments is considered optional.
At introduction of digital thread-mark it is necessary to take into account the feature of structure of files, as bases for introduction of sign. Because by basis a voice file serves for introduction, it is needed to notice that, introduction takes place in a region with surplus pcyco-visual surplus, that at the change of a few bits in this segment it will not make to the substantial loss in quality. Thus this change will not be noticeable to the human ear, because he has the threshold of sensitiveness. But it is necessary similarly to mark that in comparison of these formats the format of ??3 has the tied-up sequence of information, while a WAV-file is broken on segments. So there can be problems with introduction of large sequences of information. Consequently the format of mp3 is more acceptable to introduction of thread-marks. Masters work is not finished presently. Finishing is planed on December of 2007 year. Donetsk National Technical University> Masters portal Donetsk National Technical University> Abstract | Library | Links |