[Ffmpeg-devel] [PATCH] faad decoding error return
Wed Mar 8 12:58:18 CET 2006
On Wed, Mar 08, 2006 at 09:14:13AM +0000, Benjamin Larsson wrote:
> Mike Melanson wrote:
> > [...]
> > That's a good start. That would obviate the need for iq_table.h
> > (~250 KB). Other obvious tables:
> > * sine_win.h (~150 KB) which is a bunch of sin() values
> > * cfft_tab.h (~117 KB) has a bunch of complex constants for FFT (cos()
> > and sin() values)
> > * ic_predict.h (~15 KB) has a table of inverse exponent (right term?)
> > values (1/2, 1/4, 1/8, etc.), as well as another table I am not sure
> > of (named mnt_table, 128 values descending from .953 -> .479)
> > * kbd_win.h (~85 KB) has tables named kbd wich run from 0.0 -> 1.0;
> > what does kbd mean?
> Keiser Bessel Derived. A mdct window.
> > * ssr_win.h (~14 KB) more sine and kbd (?) tables
> > Wondering why the author(s) chose to transport these tables, I can
> > only assume they were targeting platforms that had no floating point
> > units and did not even have the support libraries to emulate the
> > functions in software. Or perhaps on platforms with flawed FP
> > functionality. I think FFmpeg at least assumes that sin() and cos()
> > will be available. And we traditionally have been apathetic toward
> > platforms deemed "broken". So it shouldn't be a problem if we want to
> > generate the tables at runtime.
> Tables are always faster then sin or cos. But there they could have
> generated them at runtime.
yes, tables should definitly be generated at runtime if possible
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