[FFmpeg-devel] [RFC] libavfilter audio API and related issues

[Michael Niedermayer]

On Wed, Jun 02, 2010 at 06:29:48AM +0000, S.N. Hemanth Meenakshisundaram wrote:
> Michael Niedermayer <michaelni <at> gmx.at> writes:
> 
> > 
> > On Sat, May 22, 2010 at 10:37:18PM -0700, S.N. Hemanth Meenakshisundaram wrote:
> > > On 05/02/2010 12:08 PM, Stefano Sabatini wrote:
> > >> On date Wednesday 2010-04-28 07:07:54 +0000, S.N. Hemanth 
> > >> Meenakshisundaram encoded:
> > >>    
> > >>> Stefano Sabatini<stefano.sabatini-lala<at>  poste.it>  writes:
> > >>>      
> > >>>> Follow some notes about a possible design for the audio support in
> > >>>> libavfilter.
> > >>>>
> > >>>> AVFilterSamples struct
> > >>>> ======================
> > >>>>
> > >>>> (Already defined in afilters, but renamed AVFilterBuffer at some
> > >>>> point.)
> > >>>>
> > >>>> Follows a possible definition (with some differences whit respect to
> > >>>> that currently implemented in afilters):
> > >>>>
> > >>>>        
> > >>> [...]
> > >>>      
> > >>    
> > >
> > > Hi,
> > >
> > > I started off trying to make the ffplay changes required for audio 
> > > [...]
> > >
> > 
> > there is nothing that prevents one from creating a file where such things
> > change. (and we try to support all files)
> > [...]
> > 
> > also please avoid memcpy() or explain why each is unavoidable in your patch
> > 
> > [...]
> > 
> 
> Hi All,
> 
> I am working on the audio structures and functions. Keeping parameters like # of
> channels at the buffer level as Michael recommended above. I have a couple of
> questions at this point:
> 
> 1. I need to use functions like avcodec_channel_layout_num_channels() from
> audioconvert.c and avcodec_channel_layout_num_channels() from resample.c
> 
> Is it ok to define new functions in libavfilter since we eventually hope to
> replace resample.c etc and also lavfi shouldn't be dependent on lavc. Please let
> me know if I should call existing functions instead.

ultimately i would like to avoid a dependancy between lavfi and lavc and
resampling being moved into lavfi and no resampling code in lavc
this though can be done once audio support is in main svn if thats easier.
we should not drag more changes in than needed


> 
> 2. If supported sample formats differ between adjacent filters, I am
> automatically inserting a resampling filter in between just as a scaling filter
> is inserted for video. But how should differences in supported channel layouts
> be handled? Should this be left to individual filters to decide?

i too think that a convertion filter should be inserted in this case

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20100603/7ffd4a5e/attachment.pgp>