[FFmpeg-devel] [PATCH] avfilter: add signalstats filter

[Stefano Sabatini]

On date Saturday 2014-06-07 11:23:47 -0400, Dave Rice encoded:
> 
> On Jun 4, 2014, at 4:36 AM, Stefano Sabatini <stefasab at gmail.com> wrote:
[...]
> >> + at end example
> >> +
> >> + at item
> >> +Output specific data about the minimum and maximum values of the Y plane per frame:
> >> + at example
> >> +ffprobe -f lavfi movie=example.mov,signalstats -show_entries frame_tags=lavfi.values.YMAX,lavfi.values.YMIN
> > 
> > Do we have a namespace resolution scheme? What about lavfi.signalstats.VAL?
> 
> Typo (earlier version of the filter was called 'values'). Corrected to lavfi.signalstats.VAL.

Please send an updated version on list, for easing review (the latest
GitHub version seems still to contain "values", so maybe you forgot to
push your updates).

You can use git-rebase -i to squash many committs together in the
final patch.

[...]
> >> +    // find low / high based on histogram percentile
> >> +    // these only need to be calculated once.
> >> +
> >> +    lowp   = s->fs  * 10 / 100;
> >> +    highp  = s->fs  * 90 / 100;
> >> +    clowp  = s->cfs * 10 / 100;
> >> +    chighp = s->cfs * 90 / 100;
> > 
> > I wonder if we should make the percentile value parametric (for
> > example setting the percentile margin M and then computing 1-M and M
> > values).
> 

> I was using ebur128 for inspiration where volume is computed at
> values at the 10% and 95% percentiles to exclude the major
> outliers. Feasibly M could be a parameter though the metadata output
> so then contain the value of M to put the high and low values into
> context.

Fine with me if you don't want to implement it.
-- 
FFmpeg = Frightening Fast Mythic Pitiless Elitist Gadget