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Co oznacza flaga "emphasis" w przypadku mp3? [w polskich interfejsach - emfaza] , kubazzz 16/04/09 02:38
Nie mogę coś wygooglować o co z tym chodziło, tylko tyle że zajmuje 2 bity i jest nieużywana obecnie.SM-S908 - tzn. szukasz więcej informacji niż tu? , Seadog 16/04/09 07:15
http://www.id3.org/mp3Framehttp://nadobranoc.weebly.com/
http://ciii.blogspot.com/ - moze tu więcej.... , DrLamok 16/04/09 09:28
z tego co na szybko poczytałem to raczej jest tam ze wzgledow historycznych :P pewnie to dali na wszelki wypadek jakby sie okazało że może być potrzebne....
drzewiej sie chyba taki zabieg ( podbicia wysokich tonów w czasie nagrywania/transmisji materiału dźwiękowego ) stosowało w celu eliminacji/redukcji szumów ? hmmm a następnie podczas odtwarzania wysokie tony musiały być odpowiednio tłumione...
http://en.wikipedia.org/...sis_(telecommunications)
http://pl.wikipedia.org/wiki/Deemfaza
Emphasis is not red-book specific. It is supported by other devices, such as minidisc recorders and the F1-type digital adapters which are defined by an EIAJ standard. As a matter of fact, the Sony PCM501/601/701 record with non-defeatable pre-emphasis, however the playback automatically switches in de-emphasis according to the emphasis bit in the recording.
Emphasis, when applied correctly in digital audio, does exactly what it was intended to do, that is reduce the noise floor. Since random noise is equal-energy-per-unit-bandwidth, while hearing is equal-energy-per-octave, each successive octave having twice the bandwidth, randim noise has most of its energy in the higher octaves. Usually random audio noise is called hiss. By boosting the higher frequencies during recording or transmission (pre-emphasis) they may be reduced in a complementary manner during playback or reception, thereby reducing the random noise introduced in the recording or transmission channel.
If de-emphasis is done in the digital domain, the result must contain more bits of precision if the S/N benefit is to be realized. That is, by de-emphasizing a 16-bit CD to a 16-bit file, you've just lost the benefit of lower noise floor. Therefore, CD players that do digital de-emphasis often have 20- or 24-bit paths after de-emphasis to preserve the lower noise floor.
De-emphasis probably fell out of favor because many early CD players used inaccurate analog R/C de-emphasis networks. This is no longer a problem as CD players almost universally do de-emphasis digitally. However, now we have a new problem, as computer audio has become a larger player. Emphasis was not originally important in computer audio and thus was ignored by many (defacto) standards and most computer hardware. It has only become important as CD audio has merged with computer audio.
Is emphasis useful? For most popular music, probably no, because the 96 dB S/N radio afforded by 16-bits with no emphasis is more than enough. Sadly. many popular recordings today are jammed up into the top few bits, not exploiting anywhere near what the CD can offer without emphasis. Emphasis would make these recordings worse, jamming them even harder against the top. However, classical recordings with wide dynamic range can benefit from emphasis. Maybe not as much as HDCD, but emphasis is an intermediate step that can be decoded by all CD players, whereas HDCD can only be decoded by a handful. And, if you want to get the best out of an emphasized CD on your Transporter, just apply the de-emphasis curve using your favorite sound editor (mine is Cool Edit) and write the result to 24-bit to preserve the benefit of emphasis.
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