[FFmpeg-devel] [PATCH] Add a new channel layout API

[Michael Niedermayer]

On Tue, Dec 25, 2018 at 02:11:45PM +0100, Paul B Mahol wrote:
> On 12/25/18, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > On Mon, Dec 24, 2018 at 06:34:30PM +0100, Paul B Mahol wrote:
> > [...]
> >> -static const char *get_channel_name(int channel_id)
> >> +const char *av_channel_name(enum AVChannel channel_id)
> >>  {
> >
> >>      if (channel_id < 0 || channel_id >= FF_ARRAY_ELEMS(channel_names))
> >>          return NULL;
> >> +    if ((unsigned) channel_id >= FF_ARRAY_ELEMS(channel_names))
> >> +        return "?";
> >
> > this looks like a untended duplicate check
> >
> > [...]
> >
> >> +/**
> >> + * Check whether two channel layouts are semantically the same, i.e. the
> >> same
> >> + * channels are present on the same positions in both.
> >> + *
> >> + * If one of the channel layouts is AV_CHANNEL_ORDER_UNSPEC, while the
> >> other is
> >> + * not, they are considered to be unequal. If both are
> >> AV_CHANNEL_ORDER_UNSPEC,
> >> + * they are considered equal iff the channel counts are the same in
> >> both.
> >> + *
> >> + * @param chl input channel layout
> >> + * @param chl1 input channel layout
> >> + * @return 0 if chl and chl1 are equal, 1 if they are not equal. A
> >> negative
> >> + *         AVERROR code if one or both are invalid.
> >> + */
> >> +int av_channel_layout_compare(const AVChannelLayout *chl, const
> >> AVChannelLayout *chl1);
> >
> > It could be usefull if this is a full compare function that allows
> > sorting/ordering
> 
> Which kind of sorting? 

it doesnt matter which sorting.
Having some allows some operations to be performed more efficient
than having none.
An example is merging 2 lists removing duplicates.
2 sorted lists can be merged in O(n) but if theres no way to sort
and just a equal / non equal check it requires O(n^2)


> That could be only added later when needed.

adding it later is fine but i think its better if the API
allows it.
This would not work with above as it requires "1 if they are not equal",
it could allow 1 or -1 (or just non zero) then it can be extended

thx

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

Whats the most studid thing your enemy could do ? Blow himself up
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