[Libav-user] [Audacity-devel] Requesting help to port Audacity to recent FFmpeg

[Michael Niedermayer]

On Wed, May 21, 2014 at 01:39:46AM +0100, Martyn Shaw wrote:
> Thanks Richard, I think you have made a good summary here.
> 
> Audacity is attempting to make itself independent of the changes in 
> libav and ffmpeg by using Gstreamer as a third-party.  I support that 
> (for now at least).  We want the functionality without the hassle.

understood, though about the "mess" some of the changes in the API
where needed so the codec can give you a buffer of the right size
instead of failing if the one you allocated was too small,
You wouldnt want to keep using an API that has such limitations,
and thats also just a one time fix, once that part of the API
is fixed it wont need to be fixed again.

And then your interface code to ffmpeg was and is alot more complex
than needed, for example the whole use of url protocol wasnt
needed (which was one thing that needed an update API wise and yes
this one resulted out of libav-ffmpeg fork mess, there was no
reason to make that API private)
but then again audacity had no need to use any of this api, and the
code is simpler without using it as well

Then there was the ffmpeg format probing code in audacity, i dont
understand why this was put there, the code is alot simpler without
it and ffmpeg will do the probing for you without that code.
Ive removed that too on the github clone and that change isnt api
update related it was just simplifying the audacity-ffmpeg interface
code.
And i suspect theres alot more that can be simplified in it, and the
amount of "api-hassle" there would be in the future should be alot
less when the interface is using only what it actually needs to


> 
> TTFN
> Martyn
> 
> On 20/05/2014 09:14, Richard Ash wrote:
> > On Wed, 14 May 2014 19:27:38 +0200
> > Michael Niedermayer <michaelni at gmx.at> wrote:
> >> On Sun, May 11, 2014 at 09:16:29PM +0200, Benjamin Drung wrote:
> >>> That's why I send this mail to this mailing list to request help. Is
> >>> there anyone who has the time and skill to help porting Audacity to
> >>> the latest FFmpeg API version?
> >>>
> >>> [1] http://bugzilla.audacityteam.org/show_bug.cgi?id=606
> >
> > I think I'm right in saying that no-one on the audacity-devel list was
> > specifically aware of this work/request (or I might have said something
> > earlier).
> >
> > As a result of this problem, one of the Audacity contributors, Leyland
> > Lucius, has been perusing the use of Gstreamer as an abstraction layer
> > for ffmpeg. This work has recently arrived in Audacity SVN, so you
> > should be able to see where it is at (it isn't working for me, but I
> > don't think it's Leyland's fault).
> >
> > The rationale for doing this is that the Gstreamer 1.0 API is much more
> > stable than the libAV one, and there is an (actively maintained)
> > gst-plugin-libav which provides the functionality of libAV through that
> > API. Thus the problem of providing up-to-date builds of libAV is
> > reduced, and an abstraction layer is provided.
> >
> > This also has the benefit of allowing (in principal) any other codecs
> > which are supported in Gstreamer (or by plugins for it) to be added to
> > Audacity relatively easily. This is something we hope to make modular,
> > so that it doesn't need a complete new build of audacity to use new
> > gstreamer plug-ins, and every download of Audacity doesn't have to ship
> > with every possible codec library.
> >
> >
> >
> > Richard
> >
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> 
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-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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