[FFmpeg-devel] [PATCH] avcodec: Add AVClass to AVCodecParameters
michael at niedermayer.cc
Tue May 10 16:28:05 CEST 2016
On Tue, May 10, 2016 at 03:53:31PM +0200, wm4 wrote:
> On Tue, 10 May 2016 14:35:02 +0200
> Michael Niedermayer <michael at niedermayer.cc> wrote:
> > On Tue, May 10, 2016 at 02:02:52PM +0200, Hendrik Leppkes wrote:
> > > On Tue, May 10, 2016 at 1:43 PM, Michael Niedermayer
> > > <michael at niedermayer.cc> wrote:
> > > > On Tue, May 10, 2016 at 11:17:12AM +0100, Derek Buitenhuis wrote:
> > > >> On 5/10/2016 7:24 AM, Hendrik Leppkes wrote:
> > > >> > I don't like this, the struct is pretty cleanly defined and unlikely
> > > >> > to be extended much over time.
> > > >> > Most other structs have AVOptions so the CLI can interact with it, but
> > > >> > this struct is not meant to be modified by users, its just a direct
> > > >> > line of communication between demuxer->decoder or encoder->muxer.
> > > >>
> > > >> To me this mostly still feels like trying to make a demuxing library
> > > >> something it isn't. It demuxes and muxes.
> > > >>
> > > >> You can argue that it should be easier than decoding a frame to get this
> > > >> info (which I don't personally think is much trouble at all). However,
> > > >> jamming it into libavformat for reasons like "we've always done this" and
> > > >> "there's no better place" is not good design IMO.
> > > >>
> > > >> It sounds like what you really want is a higher level "easy" API. Don't
> > > >> jam it in to existing decoupled APIs because it is convenient, IMO. That's
> > > >> how horrible things like having ffmpeg.c functionality in libavformat came
> > > >> to exist, and a decade of misery followed.
> > > >
> > > > This patch adds an AVClass field to AVCodecParameters like we use in
> > > > other public structures.
> > > > i fail to see how this patch is related to your reply
> > > >
> > > > What the patch does, is it makes the API more consistent and easy to
> > > > use. Users call the AVOption functions to set fields in the main
> > > > public structures, if they do that for AVCodecParameters it would
> > > > crash.
> > > > Even an empty AVClass that doesnt list options would reduce that
> > > > misery by at least not crashing but giving a clear error message.
> > > >
> > >
> > > We should not design our API around people not caring to read our API,
> > > because thats not a fight we can ever win.
> > APIs should be designed with the "Principle of least astonishment"
> > its quite surprising that AVOption APIs work with most public API
> > structures but crash with some
> > (AVPacket is another and i am of the oppinon and stated that previously
> > IIRC that it too should have a AVClass as its first element, this is
> > just hard to add as it requires ABI bumping everything which is why
> > i didnt push much for that being done, it needs to be done at a
> > time we bump all stuff for more important reasons)
> > also let me steal the text from wikipedia about the
> > Principle_of_least_astonishment, as its IMO well written
> Indeed, av_opt calls on structs which don't support it compile without
> warning, but mysteriously crash at runtime. That's a violation of this
> principle. And no, it doesn't mean that every struct should have an
> AVClass, because that would be insane.
iam not seriously suggesting to add it to every public struct but
playing devils advocate here why is that insane ?
it would actually solve the problem and be consistent
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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