Content deleted Content added
Maestro2016 (talk | contribs) No edit summary |
Maestro2016 (talk | contribs) No edit summary |
||
Line 4:
where subsequent blocks are overlapped so that
the last half of one block coincides with the first half of the next block.
This overlapping, in addition to the energy-compaction qualities of the DCT, makes the MDCT especially attractive for signal compression applications, since it helps to avoid [[compression artifact|artifacts]] stemming from the block boundaries. As a result of these advantages, the MDCT is employed in most modern [[lossy compression]] [[audio coding formats]], including [[MP3]], [[Dolby AC-3|AC-3]], [[Vorbis]], [[Windows Media Audio]], [[ATRAC]], [[Cook codec|Cook]], [[Advanced audio coding|AAC]] ([[MP4]] audio), [[G.729.1]],<ref name="Nagireddi">{{cite book |last1=Nagireddi |first1=Sivannarayana |title=VoIP Voice and Fax Signal Processing |date=2008 |publisher=[[John Wiley & Sons]] |isbn=9780470377864 |page=69 |url=https://books.google.com/books?id=5AneeZFE71MC&pg=PA69}}</ref> [[CELT]],<ref name="presentation">[http://people.xiph.org/~greg/video/linux_conf_au_CELT_2.ogv Presentation of the CELT codec] by Timothy B. Terriberry (65 minutes of video, see also [http://www.celt-codec.org/presentations/misc/lca-celt.pdf presentation slides] in PDF)</ref> [[Opus (audio format)|Opus]], and [[LDAC (codec)|LDAC]].
The discrete cosine transform (DCT) was first proposed by [[N. Ahmed|Nasir Ahmed]] in 1972,<ref name="Ahmed">{{cite journal |last=Ahmed |first=Nasir |author-link=N. Ahmed |title=How I Came Up With the Discrete Cosine Transform |journal=[[Digital Signal Processing (journal)|Digital Signal Processing]] |date=January 1991 |volume=1 |issue=1 |pages=4–5 |doi=10.1016/1051-2004(91)90086-Z |url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform}}</ref> and demonstrated by Ahmed with T. Natarajan and [[K. R. Rao]] in 1974.<ref name="pubDCT">{{Citation |first=Nasir |last=Ahmed |author1-link=N. Ahmed |first2=T. |last2=Natarajan |first3=K. R. |last3=Rao |title=Discrete Cosine Transform |journal=IEEE Transactions on Computers |date=January 1974 |volume=C-23 |issue=1 |pages=90–93 |doi=10.1109/T-C.1974.223784}}</ref> The MDCT was later proposed by John P. Princen, A.W. Johnson and Alan B. Bradley at the [[University of Surrey]] in 1987,<ref>{{cite journal |last1=Princen |first1=John P. |last2=Johnson |first2=A.W. |last3=Bradley |first3=Alan B. |title=Subband/Transform coding using filter bank designs based on time ___domain aliasing cancellation |journal=ICASSP '87. IEEE International Conference on Acoustics, Speech, and Signal Processing |date=1987 |volume=12 |pages=2161–2164 |doi=10.1109/ICASSP.1987.1169405}}</ref> following earlier work by Princen and Bradley (1986)<ref>John P. Princen, Alan B. Bradley: ''Analysis/synthesis filter bank design based on time ___domain aliasing cancellation'', IEEE Trans. Acoust. Speech Signal Processing, ''ASSP-34'' (5), 1153–1161, 1986. Described a precursor to the MDCT using a combination of discrete cosine and sine transforms.</ref> to develop the MDCT's underlying principle of '''time-___domain aliasing cancellation''' (TDAC), described below. (There also exists an analogous transform, the MDST, based on the [[discrete sine transform]], as well as other, rarely used, forms of the MDCT based on different types of DCT or DCT/DST combinations.)
| |||