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

[Michael Niedermayer]

On Tue, Nov 30, 2010 at 07:26:42PM -0800, Baptiste Coudurier wrote:
> 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.

yes


>
>>>
>>> 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.

they are already different


> I mean, the C routine is not supposed to be that fast is it ?

our code is supposed to be fast


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

just a seperate video filter that plays a bit with linesize and turns
422 in 420 as a sideeffect

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable
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