[FFmpeg-user] v360 expressions

Michael Koch astroelectronic at t-online.de
Thu Feb 27 12:09:26 EET 2020

Am 27.02.2020 um 00:14 schrieb Paul B Mahol:
> On 2/27/20, Michael Koch <astroelectronic at t-online.de> wrote:
>> Am 25.02.2020 um 11:37 schrieb Paul B Mahol:
>>> On 2/25/20, Paul B Mahol <onemda at gmail.com> wrote:
>>>> On 2/25/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>>>> Am 25.02.2020 um 10:40 schrieb Paul B Mahol:
>>>>>> On 2/25/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>>>>>> Paul,
>>>>>>>> On 2/19/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>>>>>>>> Hi,
>>>>>>>>> would it be possible to allow expressions for the yaw, pitch and
>>>>>>>>> roll
>>>>>>>>> parameters in the v360 filter? I have a project where I need these
>>>>>>>>> angles to be a function of time.
>>>>>>>> Nope, would make filter 10x times slower.
>>>>>>> Would it always slow down the filter, or only if these expressions are
>>>>>>> actually a function of time?
>>>>>>> Some nice effects would be possible when the angles and/or field of
>>>>>>> view
>>>>>>> could be functions of time.
>>>>>>> A "eval" option (like in "eq" filter) could be added to specify when
>>>>>>> to
>>>>>>> evaluate the expressions, and the default would be "init" for fast
>>>>>>> processing.
>>>>>> Eval is evil. It is not gonna be added.
>>>>> And what about sendcmd / commands?
>>>> Will look into adding it.
>>> Done.
>> I have tested it and it works to send constant values to the v360
>> filter, but it doesn't work to send an expression, as in the 3rd line of
>> this *.cmd file. With overlay filter this method works fine.
>> 0.00-1.00 v360 yaw 0;
>> 1.00-2.00 v360 yaw 60;
>> 2.00-4.00 v360 yaw 'lerp(60,120,t-2)';
>> I understand it doesn't work because v360 doesn't accept expressions.
>> Would it be possible to evaluate the expression already in sendcmd, and
>> then send the result to the target filter?
>> A workaround would be to write many lines in the *.cmd file, one line
>> for each frame.
> I told you already that expressions are evil, slow, limited and ugly.

Evil and ugly? That's no problem for me :-)  I need expressions for some 
special effects and don't care about processing speed.
Regarding "limited" I have the opposite opinion. It's a limitation not 
to have expressions.

> Use mpv player, which have support to send commands via keybindings,
> you could even write lua plugin(s).

Thanks for these hints, will have a look at them.


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