[FFmpeg-cvslog] r14956 - trunk/libavformat/matroskadec.c

[Aurelien Jacobs]

Michael Niedermayer wrote:

> On Tue, Aug 26, 2008 at 04:56:15AM +0200, Aurelien Jacobs wrote:
> > Robert Swain wrote:
> > 
> > > 2008/8/26 Aurelien Jacobs <aurel at gnuage.org>:
> > > > Robert Swain wrote:
> > > >
> > > >> 2008/8/26 Mike Melanson <mike at multimedia.cx>:
> > > >> > Michael Niedermayer wrote:
> > > >> >> On Mon, Aug 25, 2008 at 11:51:52PM +0200, Aurelien Jacobs wrote:
> > > >> >>> Mike Melanson wrote:
> > > >> >>>
> > > >> >>>> aurel wrote:
> > > >> >>>>> Author: aurel
> > > >> >>>>> Date: Mon Aug 25 01:57:29 2008
> > > >> >>>>> New Revision: 14956
> > > >> >>>>>
> > > >> >>>>> Log:
> > > >> >>>>> matroskadec: don't try to seek to negative timestamp
> > > >> >>>>> matroska timestamps are unsigned
> > > >> >>>>>
> > > >> >>>>>
> > > >> >>>>> Modified:
> > > >> >>>>>    trunk/libavformat/matroskadec.c
> > > >> >>>> Either 14955 or 14956 (both from you) broke the seek regressions.
> > > >> >>>> Representative breakage:
> > > >> >>> Grmlll... I was pretty sure those commit would change the seek
> > > >> >>> regressions. But when I wanted to test this, I just couldn't
> > > >> >>> run the test due to the wma regression (floating-point issue IIRC,
> > > >> >>> running on amd64).
> > > >> >>
> > > >> >> Which commit did cause this wma regression test failure?
> > > >
> > > > I thought it was due to r14698 as this was already discussed, and I
> > > > got the same md5. But In fact it's not.
> > > >
> > > >> > One of the 3 revisions following 14755 broke WMA. According to an
> > > >> > earlier email, it was 14758, specifically.
> > > >
> > > > Almost. It's in fact r14757 which broke reg tests for me.
> > > 
> > > Before r14757:
> > > 
> > > /* init MDCT windows : simple sinus window */
> > > for(i = 0; i < s->nb_block_sizes; i++) {
> > >     int n, j;
> > >     float alpha;
> > >     n = 1 << (s->frame_len_bits - i);
> > >     window = av_malloc(sizeof(float) * n);
> > >     alpha = M_PI / (2.0 * n);
> > >     for(j=0;j<n;j++) {
> > >         window[j] = sin((j + 0.5) * alpha);
> > >     }
> > >     s->windows[i] = window;
> > > }
> > > 
> > > Now:
> > > 
> > > // Generate a sine window.
> > > void ff_sine_window_init(float *window, int n) {
> > >     int i;
> > >     for(i = 0; i < n; i++)
> > >         window[i] = sin((i + 0.5) / (2 * n) * M_PI);
> > > }
> > > 
> > > and
> > > 
> > > /* init MDCT windows : simple sinus window */
> > > for(i = 0; i < s->nb_block_sizes; i++) {
> > >     int n;
> > >     n = 1 << (s->frame_len_bits - i);
> > >     ff_sine_window_init(ff_sine_windows[s->frame_len_bits - i - 7], n);
> > >     s->windows[i] = ff_sine_windows[s->frame_len_bits - i - 7];
> > > }
> > > 
> > > Why does this work fine with some compilers and not with others? Why
> > > does it not work fine on some archs and not others with the same
> > > compiler?
> > 
> > Difference seems to be "* alpha" vs. "/ (2 * n) * M_PI".
> > Probably a float precision/rounding issue...
> > Attached patch fixes reg tests on amd64.
> 
> patch ok

Applied.

Aurel