[Libav-user] Libavfilter - Dynamic filtergraph reconfiguration

[ilkercan Kaya]

>
> enable option is also command for every filter that supports timeline. Yes
> it looks like not documented explicitly.

Does this mean that I can set "enable" as an option? if so I tried to do
the following before initializing the filter:

if ((res = av_opt_set_int(ctx, "enable", 1, AV_OPT_SEARCH_CHILDREN)) == 0) {
    isOn = true;
} else {
    isFxBroken = true;
    LOGE("AvFX::activateFilter failed! %s %s", name,
         av_err2str(res));
}

But the call always landed on else with " AvFX::activateFilter failed!
agate Invalid argument"
Than I tried the following:

if ((res = av_opt_set(ctx, "enable", "1", AV_OPT_SEARCH_CHILDREN)) == 0) {
    isOn = true;
} else {
    isFxBroken = true;
    LOGE("AvFX::activateFilter failed! %s %s", name,
         av_err2str(res));
}

This time it did not land on else but this just makes it crash the app when
data is passed through the filtergraph with "null pointer deference on
libavfilter.so"

How may I set this enable option through the code?

On Tue, Feb 2, 2021 at 12:52 AM Paul B Mahol <onemda at gmail.com> wrote:

>
>
> On Mon, Feb 1, 2021 at 10:33 PM ilkercan Kaya <canilkerkaya at gmail.com>
> wrote:
>
>> A simpler solution, if you only need to implement enabling and disabling
>>> some of the filters, you can expect the "timeline" support does the
>>> trick:
>>
>>
>> I looked at timeline support, correct me if I am wrong but it is done
>> through the *enable_str  *property of *AVFilterContext*. It is activated
>> with *avfilter_init_str *call. This seems like setting the *enable_str  *
>> evaluation can only be done once without reiniting the whole graph. If this
>> is the case, is there a way to  pass a custom variable to the expression so
>> that I can switch it on or off? The case in the example at the
>> documentation, smartblur is hardcoded to be activated between 10 seconds to
>> 3 minutes, in my case I can not foresee when the filter will be turned
>> on/off.
>>
>
> enable option is also command for every filter that supports timeline. Yes
> it looks like not documented explicitly.
>
> Just tried it and works.
>
> mpv crowd_run_1080p50.y4m -vf "lavfi=[sendcmd=2.0 colorcorrect enable
> 0,colorcorrect=saturation=0]"
>
>
>>
>> On Mon, Feb 1, 2021 at 11:10 PM Paul B Mahol <onemda at gmail.com> wrote:
>>
>>> lowpass, highpass and agate on master git version have both timeline and
>>> command support.
>>>
>>> On Mon, Feb 1, 2021 at 7:39 PM ilkercan Kaya <canilkerkaya at gmail.com>
>>> wrote:
>>>
>>>> Hi Everyone,
>>>>
>>>> I am making a mobile music app where the user can add multiple
>>>> different FXS at runtime to current playing music through a two dimensional
>>>> pad with an effects header. I am using FFmpeg, libavfilter in C++ to add
>>>> multiple FX to the audio.
>>>>
>>>> My problem is, the user can disable any of the FX's I am using at any
>>>> time as they wish, the effects I use are agate, lowpass, highpass. The
>>>> graph is:
>>>>
>>>> abuffer -> lowpass -> highpass -> agate -> aformat -> abuffersink.
>>>>
>>>> From time to time, I want to disable some of the following  lowpass,
>>>> highpass, agate. So I thought I could just reconfigure the graph and
>>>> basically get rid of links to fulfil my wish. I am not sure this is the
>>>> right way to do it tho. I tried to dig online but all I could find was a
>>>> thread from 2012 with no conclusion. Libavfilter documentation doesn't say
>>>> anything about reconfigure or reset existing filtergraph (of that I could
>>>> find).
>>>>
>>>> What would be the best way to do this?
>>>>
>>>> Thank you!
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