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Transients

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Jean-Marc Valin 2011-02-22 17:10:45 -05:00
parent 6a2d0a0257
commit 905fa5ba04
1 changed files with 21 additions and 6 deletions
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27
doc/draft-ietf-codec-opus.xml
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@ -514,16 +514,16 @@ Insert decoder figure.
<c>tapset</c> <c>[2, 1, 1]/4</c><c>post-filter</c> <c>tapset</c> <c>[2, 1, 1]/4</c><c>post-filter</c>
<c>transient</c> <c>logp=3</c><c></c> <c>transient</c> <c>logp=3</c><c></c>
<c>coarse energy</c><c><xref target="energy-decoding"/></c><c></c> <c>coarse energy</c><c><xref target="energy-decoding"/></c><c></c>
<c>tf_change</c> <c>Section X</c><c></c> <c>tf_change</c> <c><xref target="transient-decoding"/></c><c></c>
<c>tf_select</c> <c>logp=1</c><c>Section X</c> <c>tf_select</c> <c>logp=1</c><c><xref target="transient-decoding"/></c>
<c>spread</c> <c>[7, 2, 21, 2]/32</c><c></c> <c>spread</c> <c>[7, 2, 21, 2]/32</c><c></c>
<c>dyn. alloc.</c> <c>Section X</c><c></c> <c>dyn. alloc.</c> <c><xref target="allocation"/></c><c></c>
<c>alloc. trim</c> <c>[2, 2, 5, 10, 22, 46, 22, 10, 5, 2, 2]/128</c><c></c> <c>alloc. trim</c> <c>[2, 2, 5, 10, 22, 46, 22, 10, 5, 2, 2]/128</c><c></c>
<c>skip (*)</c> <c>Section X</c><c></c> <c>skip (*)</c> <c>logp=1</c><c><xref target="allocation"/></c>
<c>intensity (*)</c><c>Section X</c><c></c> <c>intensity (*)</c><c>uniform</c><c><xref target="allocation"/></c>
<c>dual (*)</c> <c>logp=1</c><c></c> <c>dual (*)</c> <c>logp=1</c><c></c>
<c>fine energy</c> <c><xref target="energy-decoding"/></c><c></c> <c>fine energy</c> <c><xref target="energy-decoding"/></c><c></c>
<c>residual</c> <c>Section X</c><c></c> <c>residual</c> <c><xref target="PVQ-decoder"/></c><c></c>
<c>anti-collapse</c><c>logp=1</c><c>stereo && transient</c> <c>anti-collapse</c><c>logp=1</c><c>stereo && transient</c>
<c>finalize</c> <c><xref target="energy-decoding"/></c><c></c> <c>finalize</c> <c><xref target="energy-decoding"/></c><c></c>
<postamble>Order of the symbols in the CELT section of the bit-stream</postamble> <postamble>Order of the symbols in the CELT section of the bit-stream</postamble>
@ -539,6 +539,21 @@ decoding, or transmission and SHOULD take measures to conceal the error and/or r
to the application that a problem has occurred. to the application that a problem has occurred.
</t> </t>
<section anchor="transient-decoding" title="Transient Decoding">
<t>
The <spanx style="emph">transient</spanx> flag encoded in the bit-stream has a
probability of 1/8. When it is set, then the MDCT coefficients represent multiple
short MDCTs in the frame. When not set, the coefficients represent a single
long MDCT for the frame. In addition to the global transient flag is a per-band
binary flag to change the time-frequency (tf) resolution independently in each band. The
change in tf resolution is defined in tf_select_table[][] in celt.c and depends
on the frame size, whether the transient flag is set, and the value of tf_select.
The tf_select flag uses a 1/2 probability, but is only decoded
if it can have an impact on the result knowing the value of all per-band
tf_change flags.
</t>
</section>
<section anchor="energy-decoding" title="Energy Envelope Decoding"> <section anchor="energy-decoding" title="Energy Envelope Decoding">
<t> <t>
The energy of each band is extracted from the bit-stream in two steps according The energy of each band is extracted from the bit-stream in two steps according