[FFmpeg-soc] [soc]: r2856 - aac/aac.c

[Kostya]

On Sun, Jul 27, 2008 at 02:41:23PM +0200, Michael Niedermayer wrote:
> On Sun, Jul 27, 2008 at 11:53:32AM +0200, superdump wrote:
> > Author: superdump
> > Date: Sun Jul 27 11:53:32 2008
> > New Revision: 2856
> > 
> > Log:
> > Add doxygen comments for band types
> > 
> > 
> > Modified:
> >    aac/aac.c
> > 
> > Modified: aac/aac.c
> > ==============================================================================
> > --- aac/aac.c	(original)
> > +++ aac/aac.c	Sun Jul 27 11:53:32 2008
> > @@ -174,12 +174,12 @@ enum WindowSequence {
> >  };
> >  
> >  enum BandType {
> > -    ZERO_BT        = 0,
> > +    ZERO_BT        = 0,     ///< Scalefactors and spectral data are all zero.
> 
> >      FIRST_PAIR_BT  = 5,
> 
> and this one?
> 
> 
> > -    ESC_BT         = 11,
> > -    NOISE_BT       = 13,
> > -    INTENSITY_BT2  = 14,
> > -    INTENSITY_BT   = 15,
> > +    ESC_BT         = 11,    ///< Spectral data are coded with an escape sequence.
> > +    NOISE_BT       = 13,    ///< Spectral data are scaled white noise not coded in the bitstream.
> 
> > +    INTENSITY_BT2  = 14,    ///< Scalefactor data are intensity stereo positions.
> > +    INTENSITY_BT   = 15,    ///< Scalefactor data are intensity stereo positions.
> 
> what is the difference between them?
 
One is marked as for in-phase, another one is for out-of-phase intensity stereo.
Also the name is taken from the spec, I suspect there are more obscure names left there.
 
> >      ESC_FLAG       = 16,
> 
> and this?

Spec just lists for some reasons codebooks 16-31 (section 4.6.3.4), which are
really just ESC_BT (the only codebook allowing coding values up to 8191).
I think this flag can be dropped.
 
> [...]
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 
> Everything should be made as simple as possible, but not simpler.
> -- Albert Einstein