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| author | Jean-Marc Valin <jmvalin@jmvalin.ca> | 2011-09-08 01:15:34 +0400 |
|---|---|---|
| committer | Jean-Marc Valin <jmvalin@jmvalin.ca> | 2011-09-08 01:15:34 +0400 |
| commit | 4570db6af307d016d789124ad8b1990f07a8b6c7 (patch) | |
| tree | 744f3de2ee4f8cbfcf56e5bcfa4b269d7e042753 | |
| parent | 4c0e25fcdd0c156c4076a8e699b532ba7479b673 (diff) | |
Oops, remove duplicate description of the MDCT
| -rw-r--r-- | doc/draft-ietf-codec-opus.xml | 22 |
1 files changed, 4 insertions, 18 deletions
diff --git a/doc/draft-ietf-codec-opus.xml b/doc/draft-ietf-codec-opus.xml index 23305e44..097d49ed 100644 --- a/doc/draft-ietf-codec-opus.xml +++ b/doc/draft-ietf-codec-opus.xml @@ -4368,30 +4368,16 @@ multiplied by the square root of the decoded energy. This is done by denormalise <section anchor="inverse-mdct" title="Inverse MDCT"> -<t>The MDCT implementation has no special characteristics. The -input is a windowed signal (after pre-emphasis) of 2*N samples and the output is N -frequency-domain samples. A "low-overlap" window is used to reduce the algorithmic delay. -It is derived from a basic (full overlap) window that is the same as the one used in the Vorbis codec: -<figure align="center"> -<artwork align="center"><![CDATA[ - pi pi n + 1/2 2 -W(n) = [sin(-- * sin(-- * -------))] . - 2 2 L -]]></artwork> -</figure> -The low-overlap window is created by zero-padding the basic window and inserting ones in the middle, such that the resulting window still satisfies power complementarity. The MDCT is computed in mdct_forward() (mdct.c), which includes the windowing operation and a scaling of 2/N. -</t> - - <t>The inverse MDCT implementation has no special characteristics. The input is N frequency-domain samples and the output is 2*N time-domain samples, while scaling by 1/2. A "low-overlap" window is used to reduce the algorithmic delay. It is derived from a basic (full overlap) 240-sample version of the window used by the Vorbis codec: <figure align="center"> <artwork align="center"><![CDATA[ - pi pi n + 1/2 2 -W(n) = [sin(-- * sin(-- * -------))] . - 2 2 L + 2 + / /pi /pi n + 1/2\ \ \ +W(n) = |sin|-- * sin|-- * -------| | | . + \ \2 \2 L / / / ]]></artwork> </figure> The low-overlap window is created by zero-padding the basic window and inserting ones in the |