[FFmpeg-devel] [PATCH 3/7] avfilter/vf_framerate: factorize blend_frames

[Michael Niedermayer]

On Wed, Jan 03, 2018 at 08:00:24PM +0100, Marton Balint wrote:
> 
> 
> On Wed, 3 Jan 2018, Marton Balint wrote:
> 
> >
> >On Tue, 2 Jan 2018, Michael Niedermayer wrote:
> >
> >>On Sun, Dec 10, 2017 at 11:11:18PM +0100, Marton Balint wrote:
> >>>Signed-off-by: Marton Balint <cus at passwd.hu>
> >>>---
> >>> libavfilter/vf_framerate.c | 54
> >++++++----------------------------------------
> >>> 1 file changed, 7 insertions(+), 47 deletions(-)
> >>
> >>This broke fate-filter-framerate-up on x86-32 (gcc 4.8 (Ubuntu
> >4.8.5-2ubuntu1~14.04.1))
> >>
> >>--- tests/ref/fate/filter-framerate-up	2017-12-31 19:27:30.039451874
> >+0100
> >>+++ tests/data/fate/filter-framerate-up	2018-01-02 02:12:56.151674862
> >+0100
> >>@@ -4,12 +4,12 @@
> >>#dimensions 0: 320x240
> >>#sar 0: 1/1
> >>0,          0,          0,        1,   115200, 0x3744b3ed
> >>-0,          1,          1,        1,   115200, 0xc44bdc65
> >>-0,          2,          2,        1,   115200, 0xa17f0d74
> >>-0,          3,          3,        1,   115200, 0xb0c83274
> >>-0,          4,          4,        1,   115200, 0x232d6368
> >>+0,          1,          1,        1,   115200, 0x3744b3ed
> >>+0,          2,          2,        1,   115200, 0x3744b3ed
> >>+0,          3,          3,        1,   115200, 0x3744b3ed
> >>+0,          4,          4,        1,   115200, 0x6e318ba0
> >>0,          5,          5,        1,   115200, 0x6e318ba0
> >>-0,          6,          6,        1,   115200, 0x247e846e
> >>-0,          7,          7,        1,   115200, 0x89e27599
> >>-0,          8,          8,        1,   115200, 0x31c5704e
> >>-0,          9,          9,        1,   115200, 0x97e45fec
> >>+0,          6,          6,        1,   115200, 0x6e318ba0
> >>+0,          7,          7,        1,   115200, 0x6e318ba0
> >>+0,          8,          8,        1,   115200, 0x6e318ba0
> >>+0,          9,          9,        1,   115200, 0x48d65876
> >>Test filter-framerate-up failed. Look at
> >tests/data/fate/filter-framerate-up.err for details.
> >>make: *** [fate-filter-framerate-up] Error 1
> >>
> >>in master the diff now looks like this:
> >>--- tests/ref/fate/filter-framerate-up	2017-12-31 19:27:30.039451874
> >+0100
> >>+++ tests/data/fate/filter-framerate-up	2018-01-02 02:42:46.103712572
> >+0100
> >>@@ -4,12 +4,12 @@
> >>#dimensions 0: 320x240
> >>#sar 0: 1/1
> >>0,          0,          0,        1,   115200, 0x3744b3ed
> >>-0,          1,          1,        1,   115200, 0xc44bdc65
> >>+0,          1,          1,        1,   115200, 0x3744b3ed
> >>0,          2,          2,        1,   115200, 0xa17f0d74
> >>0,          3,          3,        1,   115200, 0xb0c83274
> >>0,          4,          4,        1,   115200, 0x232d6368
> >>0,          5,          5,        1,   115200, 0x6e318ba0
> >>-0,          6,          6,        1,   115200, 0x247e846e
> >>+0,          6,          6,        1,   115200, 0x6e318ba0
> >>0,          7,          7,        1,   115200, 0x89e27599
> >>0,          8,          8,        1,   115200, 0x31c5704e
> >>0,          9,          9,        1,   115200, 0x97e45fec
> >>Test filter-framerate-up failed. Look at
> >tests/data/fate/filter-framerate-up.err for details.
> >>make: *** [fate-filter-framerate-up] Error 1
> >
> >Does not happen if compiled with -O1 or -O0. With -O2 and -O3
> >fabsf(intepolate) becomes NaN.
> >
> >I am guessing that some floating point state is lost because of the SAD
> >MMX instructions, but I don't know if this is a compiler bug or something
> >should be done differently.
> >
> >Do you have an idea how to proceeed?
> 
> I guess I will just commit the patch which eliminates the floating point
> calculations, that should fix this failure as well.

yes, less fpu is better.

ive not had time to look so its a far fetched guess,
maybe something is exactly between 2 integers rounding wise and that gets
sent to different sides on different platforms

thx

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

Observe your enemies, for they first find out your faults. -- Antisthenes
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