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

[Marton Balint]

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?

Thanks,
Marton