[FFmpeg-cvslog] random thoughts about refactoring (was: Re: r20938 - trunk/libavcodec/h263.c)

[Måns Rullgård]

"Ronald S. Bultje" <rsbultje at gmail.com> writes:

> Hi,
>
> On Jan 5, 2010, at 6:18 PM, M?ns Rullg?rd <mans at mansr.com> wrote:
>> Carl Eugen Hoyos <cehoyos at ag.or.at> writes:
>>> M?ns Rullg?rd <mans <at> mansr.com> writes:
>>>>>> Also, our H.264 decoder is not a speed demon.
>>>>>
>>>>> I've read this claim before, but was never able to reproduce it
>>>>> (on a single core cpu).
>>>>
>>>> CoreAVC is ~50% faster than lavc on ARMv7 (NEON).
>>>
>>> Sorry, I meant (and tested) 32bit x86 cpu.
>>
>> Well, whatever makes it faster on ARM should be applicable anywhere.
>> The NEON asm is almost exactly the same.
>
> If x86 speed is comparable but arm isn't, and it's not the asm, then
> likely they disable some steps (postprocessing / filters?) on arm.

No, the output is bit for bit identical.  It wouldn't be a conforming
decoder otherwise.  Cache sizes may have something to do with it
though, the ARM with it's smaller caches being more sensitive to abuse
of that kind.

-- 
M?ns Rullg?rd
mans at mansr.com