[FFmpeg-user] Ffmpeg - h filter

[James Northrup]

On Wed, Jan 22, 2020 at 2:17 AM Paul B Mahol <onemda at gmail.com> wrote:

> You should never parse textual output of -h help.
>
> If you need to get options of filter use library provided API.
>

thanks Paul B Maholfor such a concise and detailed answer with such exact
references!  top posted no less!  It almost looks like anyone not writing c
code should go pound salt instead of use the executable!

so it looks like the 8 target flags has become 10.

at some point years ago i divined this struct (java interface, now
kotlin).  AVTarget appears to be missing 2 now.  Any hints?

interface AvOption {
    val optionName: String?
    val type: String?
    val targets: List<AvTarget>?
    val description: String?
    val range1: String?
    val range2: String?
    val def: String?
    val children: List<AvOption>?
    val encoding: Boolean?
    val decoding: Boolean?
    val filtering: Boolean?
    val video: Boolean?
    val audio: Boolean?
    val subtitle: Boolean?
    val export: Boolean?
    val readonly: Boolean?
    fun addChild(o: AvOption)
    enum class AvTarget {

*        Encoding, Decoding, Filtering, Video, Audio, Subtitle, Export,
Readonly*    }

    enum class AvOptionField {
        optionName, type, targets, description, range1, range2, def
    }

    companion object {
        val AV_OPT_PAT =
"^\\s+(?<${AvOptionField.optionName}>[\\w+-]+)(\\s+\\<(?<${AvOptionField.type}>\\w+)\\>)?\\s+(?<${AvOptionField.targets}>[\\w.]
{8}
)(\\s+(?<${AvOptionField.description}>[^(]+)(\\s+\\(from\\s+(?<${AvOptionField.range1}>.*)\\s+to\\s+(?<${AvOptionField.range2}>[^)]+)\\))?(\\s+\\(default\\s+(?<${AvOptionField.def}>[^)]+)\\))?)?$".toRegex().toPattern()
    }
}


> On 1/21/20, James Northrup <jim at vsiwest.com> wrote:
> > i am maintaining ffblockly which scrapes the ffmpeg executable for filter
> > parameters and defaults by cartesian product of e.g. >>>(below)
> >
> > is there a build step artifact that more cleanly has the  self-doc
> > records?  this cmdline help has changed ever so slightly and i've got to
> > reverse engineer again.  my initial look into the build process turned up
> > nothing conclusive, maybe some hints to get me started looking in the
> right
> > place
> >
> >>>>(below)
> > ffmpeg -h filter=crop 2>/dev/null
> > Filter crop
> >  Crop the input video.
> >    Inputs:
> >       #0: default (video)
> >    Outputs:
> >       #0: default (video)
> > crop AVOptions:
> >  out_w             <string>     ..FV.....T set the width crop area
> > expression (default "iw")
> >  w                 <string>     ..FV.....T set the width crop area
> > expression (default "iw")
> >  out_h             <string>     ..FV.....T set the height crop area
> > expression (default "ih")
> >  h                 <string>     ..FV.....T set the height crop area
> > expression (default "ih")
> >  x                 <string>     ..FV.....T set the x crop area expression
> > (default "(in_w-out_w)/2")
> >  y                 <string>     ..FV.....T set the y crop area expression
> > (default "(in_h-out_h)/2")
> >  keep_aspect       <boolean>    ..FV...... keep aspect ratio (default
> > false)
> >  exact             <boolean>    ..FV...... do exact cropping (default
> false)
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