Layer I,II,III and FFT |
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Layer I,II,III and FFT |
 May 5 2009, 11:03
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#1
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Group: Members Posts: 9 Joined: 21-February 08 Member No.: 51475  |
Just to make sure: Is there an FFT used in MPEG Layer I,II or III ?
Or more precisely: Is it used within the time-frequency mapping stage? It is used in the psychoacoustic model, but in the transform stage is always a (M)DCT or a hybrid of quadrature mirror filter and MDCT, isn't it? I'm asking because sometimes I see people writing something like: "Layer I: FFT with 384 samples"... 
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May 5 2009, 14:11
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#2
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 Server Admin Group: Admin Posts: 4408 Joined: 24-September 01 Member No.: 13 |
Your understanding is correct. MPEG Layer 1 and 2 just use PQMF, no MDCT (nor FFT). Layer 3 adds MDCT after PQMF.
Implementationwise you can express the MDCT as an FFT+rotation+windowing. |
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Lo-Fi Version | Time is now: 22nd November 2009 - 04:33 |
