[FFmpeg-devel] [PATCH] avfilter/vf_guided: support enhanced guided filter

[Paul B Mahol]

On Sat, Oct 23, 2021 at 4:56 AM Xuewei Meng <xwmeng96 at gmail.com> wrote:

> I would like to explain the supported modes in the guided filter,
> (1) Basic mode shows better denoising performance compared to bilateral
> filter and can be applied in many applications such as detail enhancement,
> dehazing, and so on, which is illustrated in paper
> http://kaiminghe.com/eccv10/.
>

Can you back up your claims with actual number, like what parameters were
used?


> (2) Fast basic mode is the fast algorithm of basic mode by downsampling
> method, which is recommended by http://kaiminghe.com/eccv10/. When the
> downsampling ratio is too large, blocking artifacts may occur. We can
> further improve this next step.
>

Nope, this mode is useless, it produce by default the blocking artifacts.
Provide line parameters when it can be proved useful.


>
> (3) Enhanced mode is based on the local edge information, which can better
> preserve the detailed information. We propose this mode in the second
> period of GSoC.
> (4) Fast enhanced mode is the fast algorithm of enhanced mode by
> downsampling method.
>
> And the memory reallocation is indeed an issue of this filter, which can
> be improved.
>
> All in all, we believe that guided filter is an important tool and has
> been proved to be very useful in many applications. So keep this filter is
> a better choice.
>

Citations needed.


> Some results are attached.
>


You used default parameters for bilateral filter? That is not fair
comparison.
Also you omitted speed comparison.

Of course bilateral filter implementation is recursive approximation and
does not work for very big sigmaS and sigmaR, but that is less important.


> Bests,
> Xuewei
>
>
>
> Paul B Mahol <onemda at gmail.com> 于2021年10月22日周五 下午3:28写道：
>
>>
>>
>> On Wed, Oct 13, 2021 at 3:57 PM Paul B Mahol <onemda at gmail.com> wrote:
>>
>>> Why this filter is being applied at first place at all?
>>>
>>> It is extraordinary slow and used very slow algorithm and reallocates
>>> memory all the time.
>>>
>>
>> Additionally so called fast mode, which is indeed faster than bilateral
>> filter, is unusable and have blocking artifacts.
>>
>>
>> I vote for removal of this filter.
>>
>