[FFmpeg-devel] [PATCH 1/2] opt: Add support to query ranges

[Michael Niedermayer]

On Tue, Nov 27, 2012 at 01:18:13AM +0100, Stefano Sabatini wrote:
> On date Monday 2012-11-26 02:07:51 +0100, Michael Niedermayer encoded:
> > On Mon, Nov 26, 2012 at 12:32:32AM +0100, Stefano Sabatini wrote:
> > > On date Sunday 2012-11-25 17:39:36 +0100, Michael Niedermayer encoded:
> > > > Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> > [...]
> > > > +AVOptionRanges *av_opt_query_ranges(void *obj, const char *key, int flags) {
> > > > +    const AVClass *c = *(AVClass**)obj;
> > > > +    AVOptionRanges *(*callback)(void *obj, const char *key, int flags) = NULL;
> > > > +
> > > > +    if(c->version > (52 << 16 | 8 << 9))
> > > > +        callback = c->query_ranges;
> > > > +
> > > > +    if(!callback)
> > > > +        callback = av_opt_query_ranges_default;
> > > > +
> > > > +    return callback(obj, key, flags);
> > > > +}
> > > 
> > > Note that this can't fix the list_devices problem, since that requires
> > > an already inited *instance* of a device (what we usually do, we
> > > initialize the device given the params, query the device, log the
> > > result).  This interface allows to query the class, but not the single
> > > instance (which usually requires to provide at least a few params -
> > > e.g. the device name).
> > 
> > obj is a instance, maybe i misunderstand you ?
> 
> When the code prints the options in -h full, it is passing a class (so
> there is no real object "attached" to the class). I can't imagine how
> this could be called on a real instance, assuming that the callback is
> called on the class.

the "-h" code passes a fake instance created by using a pointer to
a pointer to a AVClass, it does not pass a class


> 
> 
> > 
> > 
> > > 
> > > > +
> > > > +AVOptionRanges *av_opt_query_ranges_default(void *obj, const char *key, int flags) {
> > > > +    AVOptionRanges *ranges = av_mallocz(sizeof(*ranges));
> > > > +    AVOptionRange **range_array = av_mallocz(sizeof(void*));
> > > > +    AVOptionRange *range = av_mallocz(sizeof(*range));
> > > > +    const AVOption *field = av_opt_find(obj, key, NULL, 0, 0);
> > > > +
> > > > +    if(!ranges || !range || !range_array || !field)
> > > > +        goto fail;
> > > > +
> > > > +    ranges->range = range_array;
> > > > +    ranges->range[0] = range;
> > > > +    ranges->nb_ranges = 1;
> > > > +    range->is_range = 1;
> > > > +    range->value[0].dbl = field->min;
> > > > +    range->value[1].dbl = field->max;
> > > > +
> > > > +    switch(field->type){
> > > > +    case AV_OPT_TYPE_INT:
> > > > +    case AV_OPT_TYPE_INT64:
> > > > +    case AV_OPT_TYPE_PIXEL_FMT:
> > > > +    case AV_OPT_TYPE_SAMPLE_FMT:
> > > > +    case AV_OPT_TYPE_FLOAT:
> > > > +    case AV_OPT_TYPE_DOUBLE:
> > > > +        break;
> > > > +    case AV_OPT_TYPE_STRING:
> > > > +        range->component[0].dbl = 0;
> > > > +        range->component[1].dbl = 0x10FFFF;
> > > > +        range->value[0].dbl = -1;
> > > > +        range->value[1].dbl = INT_MAX;
> > > > +        break;
> > > > +    case AV_OPT_TYPE_RATIONAL:
> > > > +        range->component[0].dbl = INT_MIN;
> > > > +        range->component[1].dbl = INT_MAX;
> > > > +        break;
> > >
> > 
> > > > +    case AV_OPT_TYPE_IMAGE_SIZE:
> > > > +        range->component[0].dbl = 0;
> > > > +        range->component[1].dbl = INT_MAX/128/8;
> > > > +        range->value[0].dbl = 0;
> > > > +        range->value[1].dbl = INT_MAX/8;
> > > > +        break;
> > > 
> > > Uh? What's the meaning of "range" in case of an image?
> > 
> 
> > the component range is the range of the component of the vector
> 
> which vector?

when you have a width and height
these 2 form a vector of dimension 2 whichs components are
positive integer scalars.
vector = (width, height)


> 
> > the value range is the range in count of pixels
> 
> Please document this.

done


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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