On Thu, Feb 18, 2016 at 12:42:59PM +0100, Michael Niedermayer wrote: > On Thu, Feb 18, 2016 at 11:36:18AM +0100, Clément Bœsch wrote: > > Hi, > > > > While working on PNG DSP, I realized the filter up was doing extra > > overflow checks on the bytes non multiple of the long word size. This > > logic is present in both C and x86 ASM. Here is the current C code for > > reference: > > > > -------------- 8< ---------------- > > > > // 0x7f7f7f7f or 0x7f7f7f7f7f7f7f7f or whatever, depending on the cpu's > > native arithmetic size > > #define pb_7f (~0UL / 255 * 0x7f) > > #define pb_80 (~0UL / 255 * 0x80) > > > > static void add_bytes_l2_c(uint8_t *dst, uint8_t *src1, uint8_t *src2, int > > w) > > { > > long i; > > for (i = 0; i <= w - (int) sizeof(long); i += sizeof(long)) { > > long a = *(long *)(src1 + i); > > long b = *(long *)(src2 + i); > > *(long *)(dst + i) = ((a & pb_7f) + (b & pb_7f)) ^ ((a ^ b) & > > pb_80); > > } > > for (; i < w; i++) > > dst[i] = src1[i] + src2[i]; > > } > > > > -------------- 8< ---------------- > > > > The thing is, the buffers seem to be 0 padded to 16 (see > > av_fast_padded_malloc() calls). I'm assuming there are cases where it's > > not? > > isnt dst the AVFrame in one call ? > so that this would write over width if it wrote beyond ? >
but isn't frame->data[N] always padded as well...? -- Clément B.
signature.asc
Description: PGP signature
_______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel