[Libav-user] Libavfilter - Dynamic filtergraph reconfiguration

Sat Feb 6 00:06:57 EET 2021

I see and whenever I toggle my enable flag I have to recall
avfilter_init_str() to make sure filtergraph takes the newest set enable
flag right?

On Sat, Feb 6, 2021, 01:00 Paul B Mahol <onemda at gmail.com> wrote:

>
>
> On Fri, Feb 5, 2021 at 10:57 PM ilkercan Kaya <canilkerkaya at gmail.com>
> wrote:
>
>> There are two APIs to set options,
>>
>> Is the other one through a dictionary? I tried to find it through
>> examples but that's all I got.
>>
>> Could you tell me the other API so I can try to set the enable flag
>> through there.
>>
>
> The one where you concat options as string with values.... might not be
> friendly.
>
> avfilter_init_str()
>
>
>>
>> On Fri, Feb 5, 2021 at 3:25 PM Paul B Mahol <onemda at gmail.com> wrote:
>>
>>>
>>>
>>> On Fri, Feb 5, 2021 at 2:49 AM ilkercan Kaya <canilkerkaya at gmail.com>
>>> wrote:
>>>
>>>> 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?
>>>>
>>>
>>> There is nothing wrong with your code. It is just bug in libavfilter, I
>>> posted patch to fix it on devel mailing list.
>>>
>>> There are two APIs to set options, one of them is not much tested and
>>> thus it got broken.
>>>
>>>
>>>>
>>>> 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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>>>>>>>
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>>>>>>
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>>>>>
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