[FFmpeg-devel] FATE & Regressions (and PPC is broken)

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> Hi
>
> On Sun, Mar 16, 2008 at 12:26:15AM +0000, M?ns Rullg?rd wrote:
>> M?ns Rullg?rd <mans at mansr.com> writes:
>> 
>> > Diego Biurrun <diego at biurrun.de> writes:
>> >
>> >> On Sat, Mar 15, 2008 at 02:24:41AM +0100, Michael Niedermayer wrote:
>> >>> On Sat, Mar 15, 2008 at 12:36:36AM +0000, M?ns Rullg?rd wrote:
>> >>> > Mike Melanson <mike at multimedia.cx> writes:
>> >>> > 
>> >>> > > The following regression test is broken on PowerPC (gcc 4.1.2):
>> >>> > >
>> >>> > > diff -u -w
>> >>> > > "/home/melanson/ffmpeg/ffmpeg-main"/tests/ffmpeg.regression.ref
>> >>> > > tests/data/vsynth.regression
>> >>> > > --- /home/melanson/ffmpeg/ffmpeg-main/tests/ffmpeg.regression.ref
>> >>> > > 2008-03-08 19:10:07.000000000 -0800
>> >>> > > +++ tests/data/vsynth.regression        2008-03-12 14:27:53.000000000 -0700
>> >>> > > @@ -197,7 +197,7 @@
>> >>> > >  353368 ./tests/data/a-flac.flac
>> >>> > >  c4228df189aad9567a037727d0e763e4 *./tests/data/flac.vsynth.out.wav
>> >>> > >  stddev: 33.31 PSNR:65.87 bytes:1040384
>> >>> > > -a1e56bb034c2773438ba1c830c4cea07 *./tests/data/a-wmav1.asf
>> >>> > > +59575b4756d674cd8c8d53d86c08e8cb *./tests/data/a-wmav1.asf
>> >>> > >  106004 ./tests/data/a-wmav1.asf
>> >>> > >  stddev:12251.50 PSNR:14.56 bytes:1056768
>> >>> > >  stddev:2106.00 PSNR:29.85 bytes:1048576
>> >>> > > make: *** [codectest] Error 1

[...]

>> I've tracked down the real reason for the difference.  It results from
>> lost precision by use of floats in mdct.c.  Attached patch makes a few
>> temporary values double instead.  I don't know what it might do to
>> performance, though.
>
> I dont know about performance either, i guess there are some situations
> where it would be slower but systems should have asm MDCTS anyway ...
> So iam ok with the change.

Committed.

-- 
M?ns Rullg?rd
mans at mansr.com