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

[Ramiro Polla]

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?