[FFmpeg-devel] [PATCH 2/4] lavd: add device capabilities API

[Michael Niedermayer]

On Mon, Feb 17, 2014 at 05:14:32PM +0100, Lukasz M wrote:
> On 16 February 2014 18:45, Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > On Sun, Feb 16, 2014 at 01:28:03PM +0100, Lukasz Marek wrote:
> > >
> > > >>This version still has one open issue: how does it express a limited
> > set of
> > > >>frame sizes. For example, if a webcam supports exactly 640×480 and
> > 320×240.
> > > >>Does it return { 320, 640 } for the width and { 240, 480 } for the
> > height?
> > > >>Is the application supposed to try each width in turn and query the
> > > >>corresponding range for height? It works, although it is a bit
> > cumbersome,
> > > >>but it is not intuitive: maybe add a comment, or do it like that in the
> > > >>examples.
> > > >
> > > >maybe AV_OPT_TYPE_IMAGE_SIZE, should be used
> > >
> > > Can AV_OPT_TYPE_IMAGE_SIZE be represented in AVOptionRange?
> > > I'm asking because I'm willing to change that, but not sure it is
> > > doable without changing AVOptionRange struct.
> >
> > it was certainly intended to be representable
> > see for example opt_list()
> >
> > and of course things can be done differently if needed
> 
> 
> I did check it quickly and it seems image size is represented as string
> ("640x480" for example)
> I haven't found how range of image sizes should be represented.
> 
> If there is no format defined then I can propose something like that
> "100x100-640x480"
> or
> "100-640x100-480"

typedef struct AVOptionRange {
    const char *str;
    double value_min, value_max;             ///< For string ranges this represents the min/max length, for dimensions this represents the min/max pixel count
    double component_min, component_max;     ///< For string this represents the unicode range for chars, 0-127 limits to ASCII

so the current API would allow limiting the pixel count or both w,h
against the same nummeric value. Thats possibly not flexible enough

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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