[FFmpeg-devel] [PATCH 1/5] Shrink the size of vp56_mv

[Ronald S. Bultje]

Hi,

2010/6/22 M?ns Rullg?rd <mans at mansr.com>:
> "Ronald S. Bultje" <rsbultje at gmail.com> writes:
>> On Tue, Jun 15, 2010 at 2:52 PM, Reimar D?ffinger
>> <Reimar.Doeffinger at gmx.de> wrote:
>>> On Tue, Jun 15, 2010 at 04:58:14PM +0200, Aurelien Jacobs wrote:
>>>> On Tue, Jun 15, 2010 at 09:02:14AM -0400, David Conrad wrote:
>>>> > ---
>>>> > ?libavcodec/vp56.h | ? ?4 ++--
>>>> > ?1 files changed, 2 insertions(+), 2 deletions(-)
>>>> >
>>>> > diff --git a/libavcodec/vp56.h b/libavcodec/vp56.h
>>>> > index 89eba05..3d98b9e 100644
>>>> > --- a/libavcodec/vp56.h
>>>> > +++ b/libavcodec/vp56.h
>>>> > @@ -60,8 +60,8 @@ typedef struct {
>>>> > ?} VP56RefDc;
>>>> >
>>>> > ?struct vp56_mv {
>>>> > - ? ?int x;
>>>> > - ? ?int y;
>>>> > + ? ?int16_t x;
>>>> > + ? ?int16_t y;
>>>> > ?};
>>>>
>>>> Looks OK. Apply if you're sure that it can't overflow.
>>>
>>> Hm, might make sense to benchmark a bit, it might be slower e.g.
>>> if it means a lot of sign extension is added to the code...
>>
>> Did someone benchmark this? I mean, I'm quite sure any difference on
>> general decoding would be unnoticeable so I might need some pointers
>> on what exactly to benchmark, to prevent me wasting my time.
>
> A simple test is to compare the size of .text on vp[56]+.o before and
> after. ?More instructions would make it bigger.

before:

bash-3.2$ size libavcodec/vp{5,6,56}.o
__TEXT	__DATA	__OBJC	others	dec	hex
24867	68	0	57091	82026	1406a	libavcodec/vp5.o
26244	260	0	68988	95492	17504	libavcodec/vp6.o
21629	0	0	48475	70104	111d8	libavcodec/vp56.o

after:

bash-3.2$ size libavcodec/vp{5,6,56}.o
__TEXT	__DATA	__OBJC	others	dec	hex
24870	68	0	57069	82007	14057	libavcodec/vp5.o
26276	260	0	68811	95347	17473	libavcodec/vp6.o
21247	0	0	47836	69083	10ddb	libavcodec/vp56.o

So vp56.o gets smaller, vp5.o and vp6.o slightly bigger. No idea what
that means.

Ronald