On Thu, Jul 10, 2014 at 04:08:21PM +0200, Christophe Gisquet wrote: > 2014-07-10 14:53 GMT+02:00 Michael Niedermayer <michae...@gmx.at>: > > On Thu, Jul 10, 2014 at 06:47:54AM +0000, Christophe Gisquet wrote: > >> When dealing with MVs, both components may be processed at a time. > > > > mixing memory access sizes can lead to speed penalties on some cpus > > when such mixed accesses are close together > > did you benchmark this ? > > I only have a x86 platform to test it on. No, I haven't benchmarked, > nor analyzed the disassembled code. Indeed I would better, as things > sometimes work the opposite of what seemed obvious. > > (also replying to Ronald) Maybe adding some DECLARE_ALIGNED(4, ...) > where applicable would fix the alignment issue? > > Second point, can someone more used to those macros than me document > them? I guessed that in AV_[RW][BLN]: > - R/W means read/write > - Big/Little/Natural endianness
N = Native endianness > > Other aspect of this documentation: indicate that aligned addresses > may provide better performance or may be required to prevent crashes > (e.g. the 128 ones). AV_COPY, AV_SWAP, AV_ZERO AV_[RW]N[8-64]A need aligned memory AV_[RW][BLN][8-64] AV_COPY*U doesnt need aligned memory, but might be faster if its aligned. These might be slower than the "aligned only" variants > > Some of these might be obvious to most for most platforms, but still. > > -- > Christophe > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Breaking DRM is a little like attempting to break through a door even though the window is wide open and the only thing in the house is a bunch of things you dont want and which you would get tomorrow for free anyway
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