[FFmpeg-devel] [PATCH] Use LCG to generate random data for dither instead of CPU-intesive LFG.

Michael Niedermayer michaelni at gmx.at
Mon Apr 25 22:29:26 CEST 2011


On Mon, Apr 25, 2011 at 09:27:54PM +0200, Reimar Döffinger wrote:
> On Mon, Apr 25, 2011 at 09:13:17PM +0200, Michael Niedermayer wrote:
> > On Mon, Apr 25, 2011 at 08:42:21PM +0200, Reimar Döffinger wrote:
> > > I am not able to hear any difference.
> > > Differences in FATE tests:
> > > AC3:
> > > stddev:    4.91 PSNR: 82.50 MAXDIFF:   55 bytes:   804864/   804864
> > > stddev:    0.28 PSNR:107.16 MAXDIFF:    2 bytes:  1032192/  1032192
> > > 
> > > EAC3:
> > > stddev:   20.26 PSNR: 70.20 MAXDIFF: 1054 bytes:   884736/   884736
> > > stddev:   13.27 PSNR: 73.87 MAXDIFF:  215 bytes:  2998272/  2998272
> > > stddev:    5.93 PSNR: 80.87 MAXDIFF:  100 bytes:   804864/   804864
> > > (no difference in fourth test)
> > > ---
> > >  libavcodec/ac3dec.c  |    9 +++++----
> > >  libavcodec/ac3dec.h  |    2 +-
> > >  libavcodec/eac3dec.c |    6 ++++--
> > >  3 files changed, 10 insertions(+), 7 deletions(-)
> > 
> > ok, i dont understand why an LFG was used to begin with
> > i also assume you didnt pick the numbers randomly but used standard
> > constants
> 
> Not sure about the initial value, but the others are from lfg.h

The initial value is irrelevant for this use case

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

Frequently ignored awnser#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20110425/67fef3e5/attachment.asc>


More information about the ffmpeg-devel mailing list