[FFmpeg-devel] [PATCH] avfilter/select: evaluate silencedetect metadata

[Gyan Doshi]

On 2021-06-18 17:02, Timo Rothenpieler wrote:
> On 18.06.2021 06:19, Gyan Doshi wrote:
>> Instead of a specific option for silencedetect, it would be 
>> future-proof if it was an option called, say, metadata with a 
>> constant for silencedetect to start with.
>> There are multiple per-frame analysis filters like blackframe, 
>> blackdetect, freezedetect..etc and it will be easier to just extend 
>> 'metadata' with new constants
>> than to add a new option for each filter.
>
> The only issue I see with that is a loss of flexibility.
> I does not seem like you can pass parameters to variables in the 
> expression syntax.
> So there would need to be two new parameters for the select filter 
> itself.
> The start and the end marker metadata name.
>
> But what if a user wanted to combine multiple detection filters?
> I guess chaining multiple select filters would work, but can be pretty 
> annoying, depending on the usecase.
>
Yes, ideally, we would associate a function for metadata that allows it 
to be used flexibly within the expr.

See how drawtext text parameter can accommodate various functions. 
There's a limited example (last one) at 
http://www.ffmpeg.org/ffmpeg-filters.html#Examples-62

Regards,
Gyan