[FFmpeg-cvslog] r18860 - in trunk/libavcodec: ac3dec.c ac3dec_data.c ac3dec_data.h eac3dec.c

[Michael Niedermayer]

On Wed, May 20, 2009 at 09:21:11PM -0400, Justin Ruggles wrote:
> Michael Niedermayer wrote:
> > On Tue, May 19, 2009 at 10:13:34PM -0400, Justin Ruggles wrote:
> >> Michael Niedermayer wrote:
> >>> On Tue, May 19, 2009 at 06:23:38PM -0400, Justin Ruggles wrote:
> >>>> Michael Niedermayer wrote:
> >>>>> On Sun, May 17, 2009 at 08:53:27AM +0200, jbr wrote:
> >>>>>> Author: jbr
> >>>>>> Date: Sun May 17 08:53:24 2009
> >>>>>> New Revision: 18860
> >>>>>>
> >>>>>> Log:
> >>>>>> eac3dec: use 16-bit pre-mantissas instead of 24-bit in AHT decoding. it is
> >>>>>> simpler and also fixes a bug in GAQ dequantization.
> >>>>> are you sure 16bit precission is enough for that?
> >>>>> what effect does this compared to double precission floats have on the
> >>>>> PSNR ?
> >>>> stddev:    7.95 PSNR: 78.30 bytes:  3999744/  3999744
> >>> and what is that?
> >>>
> >>> we have raw -> encoder -> ac3 -> double fp decoder -> raw2
> >>>                               -> 16bit     decoder -> raw3
> >>>
> >>> PSNR of raw2 - raw vs. PSNR raw3 - raw is what we care about.
> >>> That would make 2 PSNR scores though, a before and a after
> >>>
> >>> the second part we care about is the difference to a reference decoder
> >>> that should mention which reference decoder is used though
> >> I can't compare to raw in this case because I don't have access to a
> >> professional E-AC-3 encoder which uses the AHT quantization.  But I can
> >> compare to decoded output from Nero's E-AC-3 decoder.
> >>
> > 
> >> nero vs. ffac3 svn
> >> stddev:  131.16 PSNR: 53.96 bytes:  3998716/  3999744
> > 
> > why does the output differ so much to begin with?
> 
> That I'm really not sure of.  I don't have access to the Nero decoder
> other than begging madshi to decode samples for me like I did in this case.

isnt there some official reference decoder like with ISO/ITU standards?


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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