On 2021-06-18 17:27, Timo Rothenpieler wrote:
On 18.06.2021 13:46, Gyan Doshi wrote:
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
The drawtext filter does not use expression evaluation for its text
parameter.
It implements its own logic for that, and it's purely text-replace.
The expression parser does support functions, but only functions with
one or two numeric arguments.
So it'll have to be something like detected(silence) and then silence
is a constant numeric variable that the detected function resolves to
the specific metadata names.
Yeah, so I guess this patch can go ahead as-is, and I'll look into
extending eval with a metadata(key) function for a generic facility.
Regards,
Gyan
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