[FFmpeg-devel] ffvorbis, inverted output

[Michael Niedermayer]

On Sun, Sep 28, 2008 at 03:17:29PM +0100, Robert Swain wrote:
> 2008/9/28 Michael Niedermayer <michaelni at gmx.at>:
> > On Sun, Sep 28, 2008 at 03:00:39AM +0300, Siarhei Siamashka wrote:
> >> On Saturday 27 September 2008, Siarhei Siamashka wrote:
> >> > On Sunday 14 September 2008, Michael Niedermayer wrote:
> >> > > On Sun, Sep 14, 2008 at 04:50:59AM +0300, Siarhei Siamashka wrote:
> >> > > > Hi,
> >> > > >
> >> > > > I tried to do PSNR comparison of libvorbis/ffvorbis/tremor and noticed
> >> > > > that output from ffvorbis is actually inverted (ex. output 0xFFFF in
> >> > > > libvorbis corresponds to 0x0001 in ffvorbis and so on) when compared to
> >> > > > the output from the other decoders.
> >> > > >
> >> > > > Should this be fixed?
> >> > >
> >> > > yes, if all (/most) other vorbis decoders match and we differ from that
> >> >
> >> > Can these two patches be used as a fix? The first one adds support for
> >> > scaled imdct output. The second one inverts output of the decoder (to match
> >> > libvorbis and tremor) using negative scale factor.
> >> >
> >> > As additional bonus, 'copy_normalize' function from vorbis decoder is
> >> > simplified. Though I get some inconsistent benchmark results (performance
> >> > difference is negligible with one or another variant getting ahead
> >> > randomly) and would like someone to confirm that there is no performance
> >> > regression.
> >> >
> >> > Getting scaled imdct output involves sqrt operation and scale factor uses
> >> > odd power of two, so there is some difference in PSNR compared to SVN
> >> > trunk (taking inversion into account):
> >> >
> >> > stddev:    0.02 PSNR:127.97 bytes: 22057216/ 22057216
> >>
> >
> >> Oops, an extra patch to ensure tables alignment is also needed. It is
> >> attached.
> >
> > patch ok
> 
> Just 03_vorbis_vwin_tables_align.diff or all? I guess you meant just 03.

i meant just 03 here, yes

[...] 

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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