[vlc-devel] Filters in libvlc

jboileau jboileau at gmail.com
Wed Jun 18 16:59:41 CEST 2008


you can also find me on Videolan's IRC channel if you want.

Jacques Boileau

On Wed, Jun 18, 2008 at 10:50 AM, jboileau <jboileau at gmail.com> wrote:
> Hi Lukas,
> As I said I am taking our conversation to the list so that others may
> participate in the disscussion.
> Yes, dionoea is right, I am working on a filter API for libvlc. I need
> access to 4 filters: adjust, marq, logo and magnify.
> I have taken a look at your code. And again dionoea is right: your
> approach in get_adjust_module will remove any other filters that may
> be present. But dionoea's filter API makes it easy to fix that. This
> API works great and is easy to use. I will post my code for the adjust
> filter in videolan's pastebin so you can take a quick look and see how
> the filter API is used. Its here: http://paste.videolan.org/4339
> Now here are a few pointer:
> - Adding and setting filters apply only to the current vout and are
> not kept for the next vout. They must also be saved in the config if
> we want the changes to be permanent. At least one filter, magnify,
> kills and restarts vout and all other filter's settings are lost.
> - Adding a filter through the use of var_SetString does not take
> effect instantly. So if you have code that adds a filter and
> immediatly tries to set an option of the filter it will not work. The
> filter API adds a filter and the filter is usable right away,
> What I have been trying to do for persistence, is add code to the
> filter API  to also save filters to the config. The code I have done
> is here: http://paste.videolan.org/4341 It works partly, the filter
> stays even when vout is deleted and recreated, but the options to the
> filter are lost. This code must be called at the end of
> filter_chain_AppendFilter and filter_chain_DeleteFilter. But, has
> dionoea pointed out, it is more a patch/kludge than a real solution.
> My problem is that my knowledge of the inner workings of VLC is
> extremely limited and I hit a brick wall rather quickly.
> I hope I am helping. Please ask all the questions you may have, I am
> glad if my little experience in this can be of help to you. Of course,
> only one API for filters is needed, since you are embarking on a GSoC
> project I will let you take the lead. But I will be glad to help you
> out. We should communicate and combine our efforts as much as
> possible.
> Jacques Boileau
> On Wed, Jun 18, 2008 at 9:01 AM, Lukas Durfina <lukas.durfina at gmail.com> wrote:
>> Hi,
>>  afaik you are working on filters in libvlc.
>> My knowledge is a bit poor about that, but I am
>> working on my GSoC project with phonon backend
>> and I need for example functions which can set
>> brightness, contrast, hue and so on (adjust filter).
>> I add them to libvlc, but dioneoa said me, that if I add
>> that filter, I drop all other filters. And that I should
>> talk and cooperate with you.
>> You can take a look on what I add:
>> http://git.videolan.org/?p=vlc-lukas.git;a=commitdiff;h=f2a0ab3b53294d34491c54c28f89762d6a67d6fb
>>   or directly
>> http://git.videolan.org/?p=vlc-lukas.git;a=blob;f=src/control/video.c;h=b4f3f5647f6b6b62a7678c6087aaabc8e3845b10;hb=HEAD
>> Now I know, that there is some filter chain, probably you work on it
>> and have better knowledge of it than me, so maybe
>> I can help you to make it working.
>> Lukas

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