[FFmpeg-devel] [PATCH] improve yuv422p to rgb in libswscale

[Baptiste Coudurier]

On 11/30/2010 07:13 PM, Michael Niedermayer wrote:
> On Tue, Nov 30, 2010 at 07:05:05PM -0800, Baptiste Coudurier wrote:
>> On 11/30/2010 06:53 PM, Michael Niedermayer wrote:
>>> On Tue, Nov 30, 2010 at 06:29:32PM -0800, Baptiste Coudurier wrote:
>>>> On 11/30/2010 06:15 PM, Michael Niedermayer wrote:
>>>>> On Tue, Nov 30, 2010 at 05:20:42PM -0800, Baptiste Coudurier wrote:
>>>>>> On 11/30/2010 05:13 PM, Michael Niedermayer wrote:
>>>>>>> On Tue, Nov 30, 2010 at 04:07:20AM -0800, Baptiste Coudurier wrote:
>>>>>>>> Hi
>>>>>>>>
>>>>>>>> $subject, use full vertical data when convert 422p, improve quality a lot.
>>>>>>>>
>>>>>>>> --
>>>>>>>> Baptiste COUDURIER
>>>>>>>> Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
>>>>>>>> FFmpeg maintainer                                  http://www.ffmpeg.org
>>>>>>>
>>>>>>>>      x86/yuv2rgb_template.c |   25 ++++-------
>>>>>>>>      yuv2rgb.c              |  109 ++++++-------------------------------------------
>>>>>>>>      2 files changed, 26 insertions(+), 108 deletions(-)
>>>>>>>> 16f384c9b114c76572a539511c42267ce2942c67  yuv422p_to_rgb.patch
>>>>>>>
>>>>>>> this looks like it would make 420p->rgb quite a bit slower.
>>>>>>
>>>>>> Do you think changing>>1 to>>vshift would make is quite a bit slower ?
>>>>>
>>>>> no but that stuff:
>>>>> @@ -152,134 +144,102 @@
>>>>>     YUV2RGBFUNC(yuv2rgb_c_48, uint8_t, 0)
>>>>>         LOADCHROMA(0);
>>>>>         PUTRGB48(dst_1,py_1,0);
>>>>> -    PUTRGB48(dst_2,py_2,0);
>>>>>
>>>>>         LOADCHROMA(1);
>>>>> -    PUTRGB48(dst_2,py_2,1);
>>>>>         PUTRGB48(dst_1,py_1,1);
>>>>>
>>>>>         LOADCHROMA(2);
>>>>>         PUTRGB48(dst_1,py_1,2);
>>>>> -    PUTRGB48(dst_2,py_2,2);
>>>>>
>>>>>         LOADCHROMA(3);
>>>>> -    PUTRGB48(dst_2,py_2,3);
>>>>>         PUTRGB48(dst_1,py_1,3);
>>>>>     ENDYUV2RGBLINE(48)
>>>>>         LOADCHROMA(0);
>>>>>         PUTRGB48(dst_1,py_1,0);
>>>>> -    PUTRGB48(dst_2,py_2,0);
>>>>>
>>>>>         LOADCHROMA(1);
>>>>> -    PUTRGB48(dst_2,py_2,1);
>>>>>         PUTRGB48(dst_1,py_1,1);
>>>>>     ENDYUV2RGBFUNC()
>>>>>
>>>>> and then running the code twice
>>>>
>>>> This is the C code, the mmx routine for yuv420 to rgb24 is already present.
>>>>
>>>> I don't understand running the code twice, can you please clarify ?
>>>
>>> yes, iam seeing this:
>>> -    for (y=0; y<srcSliceH; y+=2) {\
>>> +    for (y=0; y<srcSliceH; y++) {\
>>>
>>> and thus iam thinking it runs the code twice after the patch,
>>> do i miss something?
>>
>> The old code was processing 2 lines at once, see py_1 and py_2, that's
>> why a lot of code is removed in the macros.
>
> yes but i think its slower after the patch

I guess it is a bit slower because of LOADCHROMA.

>>
>> Do you agree that the mmx change looks trivial ?
>
> yes mmx looks good

Well, problem now is that mmx routine will have different behaviour, and 
will be better.
I mean, the C routine is not supposed to be that fast is it ?

Also adding a check for some user parameters would require adding tests 
in a lot of places I fear.

-- 
Baptiste COUDURIER
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
FFmpeg maintainer                                  http://www.ffmpeg.org