[Libav-user] Libavfilter - Dynamic filtergraph reconfiguration
Paul B Mahol
onemda at gmail.com
Sat Feb 6 00:10:38 EET 2021
Nope, initialization is done only once, To set options at runtime
use avfilter_graph_send_command()
On Fri, Feb 5, 2021 at 11:07 PM ilkercan Kaya <canilkerkaya at gmail.com>
wrote:
> 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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