Re: [Libquicktime-devel] Prores codec issues.

[Joseph A. <jo...@mi...>]

Oops, that bug was introduced by me. No surprise it went unnoticed for a 
while, as I am not using libquicktime's color conversion code.


On 08/11/2012 09:30, Al Crate wrote:
> The better solution was to fix the actual bug..
>
> In the colorspace_macros.h
>
> #define YUV_10_TO_RGB_24(y,u,v,r,g,b) \
>     i_tmp=(yj_16_to_rgb * (y-0x40) + vj_16_to_r * (v-0x200))>>18;        \
>     r = RECLIP_8(i_tmp);\
>     i_tmp=(yj_16_to_rgb * (y-0x40) + uj_16_to_g * (u-0x200)+ vj_16_to_g *
> (v-0x200))>>18; \
>     g = RECLIP_8(i_tmp);\
>     i_tmp=(yj_16_to_rgb * (y-0x40) + uj_16_to_b * (u-0x200))>>18; \
>     b = RECLIP_8(i_tmp);
>
> should actually be
>
> #define YUV_10_TO_RGB_24(y,u,v,r,g,b) \
>     i_tmp=(y_16_to_rgb * (y-0x40) + v_16_to_r * (v-0x200))>>18;        \
>     r = RECLIP_8(i_tmp);\
>     i_tmp=(y_16_to_rgb * (y-0x40) + u_16_to_g * (u-0x200)+ v_16_to_g *
> (v-0x200))>>18; \
>     g = RECLIP_8(i_tmp);\
>     i_tmp=(y_16_to_rgb * (y-0x40) + u_16_to_b * (u-0x200))>>18; \
>     b = RECLIP_8(i_tmp);
>
> It was using the full range functions by mistake, output is now correct.
>
> cheers
>
> On 07/11/12 17:48, Burkhard Plaum wrote:
>> Hi,
>>
>> Am 07.11.2012 17:50, schrieb Al Crate:
>>> You can easily see this by running lqt_transcode on a prores mov.
>>>
>>>
>>>
>>> On 07/11/12 12:00, Al Crate wrote:
>>>> Hi, have been playing with the ProRes codec, seems to encode correctly,
>>>> but on decode the output is noticeably darker than the original.
>>>>
>>>> Has anyone else noticed this ?
>>>>
>>>> I've tried using ffmpeg directly and that works as expected. So I'm
>>>> suspecting libquicktimes conversion from YUV422P10 to RGB888.
>>>>
>> Well then you can fix the conversion or bypass the built in colormodel converter
>> completely. It's incredibly inefficient and only here for compatibility reasons.
>>
>> Too dark video is often related to a confusion of video scaled and JPEG scaled
>> YCbCr. Not sure if that applies here.
>>
>> Burkhard
>>
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-- 
Joseph Artsimovich
Senior C++ Applications Developer
MirriAd Ltd