[FFmpeg-devel] [PACTH] Change av_get_channel_layout() syntax

[Michael Niedermayer]

On Tue, Oct 15, 2013 at 10:48:35AM +0200, Stefano Sabatini wrote:
> On date Tuesday 2013-10-15 09:54:15 +0200, Michael Niedermayer encoded:
> > On Tue, Oct 15, 2013 at 01:33:19AM +0200, Stefano Sabatini wrote:
> > > On date Sunday 2013-10-13 17:57:48 +0200, Michael Niedermayer encoded:
> > > > On Fri, Oct 04, 2013 at 05:05:38PM +0200, Stefano Sabatini wrote:
> > > [...] 
> > > > >  channel_layout.c |   21 ++++++++++++++++++---
> > > > >  channel_layout.h |    9 +++++++--
> > > > >  internal.h       |    5 +++++
> > > > >  version.h        |    3 +++
> > > > >  4 files changed, 33 insertions(+), 5 deletions(-)
> > > > > 43b5009e71e91a5be2e253a05123d294f888ccfd  0004-lavu-channel_layout-change-av_get_channel_layout-beh.patch
> > > > > From 1743fb2c469f71fc2a37a50a15e0bbcd9174c441 Mon Sep 17 00:00:00 2001
> > > > > From: Stefano Sabatini <stefasab at gmail.com>
> > > > > Date: Fri, 4 Oct 2013 15:20:50 +0200
> > > > > Subject: [PATCH] lavu/channel_layout: change av_get_channel_layout() behavior
> > > > >  at the next bump
> > > > > 
> > > > > This is done introducing a compatibility option. The new syntax is
> > > > > preferred since it allows backward syntax compatibility with libswr when
> > > > > switching to the new option handling code with
> > > > > AV_OPT_TYPE_CHANNEL_LAYOUT.
> > > > > 
> > > > > With the new parser the string:
> > > > > 1234
> > > > > 
> > > > > is interpreted as a channel layout mask, rather than as a number of
> > > > > channels, and thus it's compatible with the current way to set a channel
> > > > > layout as an integer (for the icl and ocl options) making use of integer
> > > > > option values.
> > > > > 
> > > > > ff_get_channel_layout() with compat=0 will be used in the
> > > > > AV_OPT_TYPE_CHANNEL handler code.
> > > > > ---
> > > > >  libavutil/channel_layout.c | 21 ++++++++++++++++++---
> > > > >  libavutil/channel_layout.h |  9 +++++++--
> > > > >  libavutil/internal.h       |  5 +++++
> > > > >  libavutil/version.h        |  3 +++
> > > > >  4 files changed, 33 insertions(+), 5 deletions(-)
> > > [...]
> > > > > diff --git a/libavutil/channel_layout.h b/libavutil/channel_layout.h
> > > > > index 2906098..0f3eb4e 100644
> > > > > --- a/libavutil/channel_layout.h
> > > > > +++ b/libavutil/channel_layout.h
> > > > > @@ -132,11 +132,16 @@ enum AVMatrixEncoding {
> > > > >   *   SL, SR, TC, TFL, TFC, TFR, TBL, TBC, TBR, DL, DR);
> > > > >   * - a number of channels, in decimal, optionally followed by 'c', yielding
> > > > >   *   the default channel layout for that number of channels (@see
> > > > > - *   av_get_default_channel_layout);
> > > > > + *   av_get_default_channel_layout());
> > > > > + *   Note: the use of the following character 'c' to specify a number
> > > > > + *   of channels will be required since the next major bump to make
> > > > > + *   the syntax not ambiguous.
> > > > >   * - a channel layout mask, in hexadecimal starting with "0x" (see the
> > > > >   *   AV_CH_* macros).
> > > > 
> > > 
> > > > > + *   Note: since the next major bump a channel layout mask can also be
> > > > > + *   specified with a decimal number (iff not followed by "c").
> > > > 
> > > > maybe leave this "undefined" or deprecated or something
> > > > as its rather ugly but iam fine with it as is too
> > > 
> > > Can't really understand what this sentence is referring to.
> > 
> 
> > i just meant that we could deprecate the use of decimal numbers for
> > channel masks as its somewhat odd and allows typos (lost c letter)
> > that is
> > 0x123 -> channel mask
> > 12c   -> channel count
> > 55    -> interpreted as mask for compatibility but deprecated
> 
> decimal syntax as channel mask is currently not supported, but it will
> be at the next major bump (in order to emulate the way we set channel
> layouts in lswr). So I can't see how we can deprecate something which
> is not yet supported.

i meant that it should be deprecated for lswr to do that and also
probably the newly added stuff shouldnt really recommand its use

but thats just a suggestion, as the decimal variant seems ambigous
if one doesnt "know" how its exactly interpreted



[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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