[FFmpeg-devel] [PATCH 7/9] hevc: use intreadwrite

Christophe Gisquet christophe.gisquet at gmail.com
Thu Jul 10 16:08:21 CEST 2014

2014-07-10 14:53 GMT+02:00 Michael Niedermayer <michaelni at 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

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).

Some of these might be obvious to most for most platforms, but still.


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