[FFmpeg-devel] [PATCH] swscale: avoid overread in planar2x

[Ramiro Polla]

On Sun, Sep 12, 2010 at 11:33 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sun, Sep 12, 2010 at 11:16:53AM -0300, Ramiro Polla wrote:
>> On Sun, Sep 12, 2010 at 10:43 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Sun, Sep 12, 2010 at 10:00:07AM -0300, Ramiro Polla wrote:
>> >> On Sun, Sep 12, 2010 at 7:44 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> [...]
>> >> > after a second look i see that the C code overrides the first pixel and thus
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> >> > the output should not be affected, still my suggestion though seems nicer than
>> >> > requireing all buffers to have a byte allocated before them
>> >>
>> >> Thanks for the suggestion. Patch attached. No speed difference measured.
>> >
>> >> ?rgb2rgb_template.c | ? ?4 +++-
>> >> ?1 file changed, 3 insertions(+), 1 deletion(-)
>> >> 9c5b0f0bc55c99bcfbda486bff43d26c34cb96f5 ?planar2x_avoid_overread_2.diff
>> >> Index: rgb2rgb_template.c
>> >> ===================================================================
>> >> --- rgb2rgb_template.c ? ? ? ?(revision 32166)
>> >> +++ rgb2rgb_template.c ? ? ? ?(working copy)
>> >> @@ -1773,12 +1773,13 @@ static inline void RENAME(planar2x)(const uint8_t
>> >> ? ? ? ? ?const x86_reg mmxSize= srcWidth&~15;
>> >> ? ? ? ? ?__asm__ volatile(
>> >> ? ? ? ? ? ? ?"mov ? ? ? ? ? %4, %%"REG_a" ? ? ? ? ? ?\n\t"
>> >> + ? ? ? ? ? ?"movq ? ? ? ? (%0, %%"REG_a"), %%mm4 ? ?\n\t"
>> >> + ? ? ? ? ? ?"psllq ? ? ? ? ? ? ? ? ? ? $8, %%mm4 ? ?\n\t"
>> >
>> > the first value is then 0 which would lead to a darker border pixel
>>
>> Which is overwritten by the C code. Or did I miss something?
>
> dont you want to beat the c code speedwise?

I didn't at first, but thanks for the push =). Patch attached.

before:
63750690 dezicycles in yuv410p 2048x2048 --> yuv420p 2048x2048, 2048
runs, 0 skips
after:
62768947 dezicycles in yuv410p 2048x2048 --> yuv420p 2048x2048, 2048
runs, 0 skips
-------------- next part --------------
A non-text attachment was scrubbed...
Name: planar2x_avoid_overread_3.diff
Type: text/x-patch
Size: 3072 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20100912/e7cb905a/attachment.bin>