[FFmpeg-devel] [PATCH] Move stream_options to avformat

[Michael Niedermayer]

On Sun, Jan 25, 2015 at 05:15:33PM +0100, wm4 wrote:
> On Sun, 25 Jan 2015 13:39:10 +0100
> Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > On Sun, Jan 25, 2015 at 01:18:31PM +0100, Michael Niedermayer wrote:
> > > On Sun, Jan 25, 2015 at 12:15:40PM +0100, Reimar Döffinger wrote:
> > > > On 25.01.2015, at 03:08, Michael Niedermayer <michaelni at gmx.at> wrote:
> > > > > On Sun, Jan 25, 2015 at 02:31:33AM +0100, wm4 wrote:
> > > > >> 
> > > > >>>> 
> > > > >>>> As an experienced API user, I don't have the slightest clue what I'd do
> > > > >>>> with this API, or where to find information about it.
> > > > >>> 
> > > > >>> the primary goal is to remove duplicated disposition type tables,
> > > > >>> which needs one of the tables to be public first
> > > > >>> 
> > > > >>> [...]
> > > > >> 
> > > > >> And this is the most awkward way you could find to do this?
> > > > > 
> > > > > No, i could certainly find a more akward way, if people prefer
> > > > > 
> > > > > this is just the way that would be a big step towards consistent
> > > > > and simple access to the structs
> > > > > All public structs use AVClass and AVOptions to allow applications
> > > > > to extract/enumerate fields except a few like AVStream
> > > > > this patch would add these AVClass & AVOption for AVStream, its
> > > > > indeed not populated for all fields and AVStream doesnt have a
> > > > > AVClass as its first field due to ABI. But its a step toward it
> > > > > 
> > > > > Would people prefer that each field in AVStream has a custom and
> > > > > different way to access it, as long as it looks simpler when looked
> > > > > at in isolation ?
> > > > 
> > > > Sorry if it's useless of me to only state some obvious questions, but:
> > > > I think it's clear we all want a simple, obvious and consistent API :)
> > > > If it's a bit messy, might there be a point in holding off a bit so we aren't stuck with something complicated?
> > > > Could possibly another approach after a major bump be nicer?
> > > > Or maybe better documentation/examples?
> > > 
> > > > I think this started with a valid complaint/concern but unfortunately no better alternative, could we stick to considering that instead of going over to agressive rhethoric?
> > > 
> > > absolutley
> > > i would strongly prefer if others could take this over, my interrest
> > > was just in the technical side and i wanted to move AVStream to
> > > the same system we use for all other structs. As well as fixing the
> > > quite valid issue nicolas had raised with the duplicated tables.
> > > I am quite surprised that others dont see this as a clear and
> > > uncontroversal step, there really are just
> > > 1. If we want AVStream to be consistent with other structs, that means
> > >    AVOption & AVClass. And this patch is a step toward it, one could
> > >    make a bigger or smaller step but its then either more or less
> > >    code not different code.
> > > 2. There could be a different system be used for this field or for
> > >    AVStream, this would be inconsistent
> > > 3. We can implement both a system based on AVOptions/AVClass and a
> > >    system without them, why would this field that noone cared about
> > >    until now need this, iam not sure though
> > > 4. We can leave the triplicated tables as is and hope not to forget
> > >    updating them in sync
> > > 
> > > To me the best choice is clear, move toward the same system we use
> > > elsewhere. Change that system everywhere if it could be improved
> > > I see nothing controversal on this patch but others do apparently.
> > > As i dont see what issue people have with this, i certainly cannot
> > > help fixing the patch. But iam happy to review & approve the solution
> > > that people do prefer
> > 
> > About the documentation & example side, i dont think this should yet
> > be used from outside, its only a partial implementation of AVOption
> > for AVStream, a full implementation needs a ABI bump due to the
> > first field needing to be a AVClass
> > 
> > [...]
> > 
> 
> How is it even consistent with "other structs"? Doesn't it just resolve
> flags? Resolving flags with a complicated AVOption contraption (which
> every user has to understand and duplicate) doesn't seem like a good
> choice to me at all. I hear about API users fighting with the basics of
> the FFmpeg API because it's so weird and complicated; seeing patches
> like this just feel like a bad joke in contrast.
> 

> What's wrong with:
> 
>     int av_parse_disposition_flags(const char *s);

* requires more code to use once the first field of AVStream is made an
AVClass
compare:

myctx->disposition = av_parse_disposition_flags(mystring);

vs.

av_opt_set(myctx, "disposition", mystring, 0);


* Supports just a subset of the features:
like "-forced" to remove the "forced" disposition type while leaving
the other flags in place

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

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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