[FFmpeg-devel] [PATCH] Common ACELP routines (3/3) - LPC decoding routines

[Michael Niedermayer]

On Thu, Apr 24, 2008 at 09:44:17PM +0700, Vladimir Voroshilov wrote:
> On Thu, Apr 24, 2008 at 7:21 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Thu, Apr 24, 2008 at 02:53:33AM +0700, Vladimir Voroshilov wrote:
> >  > Michael Niedermayer wrote:
> >  [...]
> >
> > >
> >  > >
> >  > > [...]
> >  > > > +void ff_acelp_reorder_lsf(int16_t* lsfq, int16_t lsfq_min_distance, int16_t lsfq_min, int16_t lsfq_max)
> >  > > > +{
> >  > > > +    int i;
> >  > > > +
> >  > > > +    lsfq[0] = FFMAX(lsfq[0], lsfq_min); //Is warning required ?
> >  > > > +
> >  > > > +    for(i=0;i<9; i++)
> >  > > > +        lsfq[i+1] = FFMAX(lsfq[i+1], lsfq[i] + lsfq_min_distance);
> >  > >
> >  > > simplification stolen from soc/amrnbdec.c:
> >  > >
> >  > > for(i=0; i<10; i++){
> >  > >     lsf[i] = FFMAX(lsf[i], lsf_min);
> >  > >     lsf_min = lsf[i] + min_distance;
> >  > > }
> >  > >
> >  > > also id make lsfq_min_distance and lsfq_min/max int
> >  > >
> >  > > ahh, and reorder_lsf() in soc/amrnbdec.c is buggy (uninitalized var)
> >  >
> >  > It also assumes that LSFs already ordered.
> >  > G.729 explicitly sorts them.
> >  > Should i put sorting code inside routine?
> >
> >  If its fast for the case that they are already sorted ...
> 
> It was written by you :)

Indeed, but ive not written it to be fast but rather simple.
Heres one which should be O(n) for already sorted lists.

for(i=0; i<N-1; i++){
    for(j=i; j>=0 && lsfq[j] > lsfq[j+1]; j--)
        FFSWAP(int16_t, lsfq[j], lsfq[j+1]);
}



> 
> >  > +/**
> >  > + * \brief decodes polynomial coefficients from LSP
> >
> > > + * \param f [out] (Q24) decoded polynomial coefficients
> >  > + * \param lsp (Q15) LSP coefficients
> >  > + */
> >  > +static void lsp2poly(int* f, const int16_t* lsp)
> >
> > > +{
> >  > +    int i, j;
> >  > +
> >  > +    f[0] = 0x1000000;          // 1.0 in Q24
> >  > +    f[1] = -lsp[0] << 10;      // *2 and Q15 -> Q24
> >  > +
> >  > +    for(i=2; i<=5; i++)
> >  > +    {
> >  > +        f[i] = f[i-2];
> >  > +
> >  > +        for(j=i; j>1; j--)
> >  > +#ifdef G729_BITEXACT
> >
> > > +            f[j] -= (mul_24_15(f[j-1]>>1, lsp[2*i-2])<<2) - f[j-2];
> >  > +#else
> >
> >  > +            f[j] -= (mul_24_15(f[j-1], lsp[2*i-2])<<1) - f[j-2];
> >
> >  Does this need the cliping from mul_24_15() ? or can it be replaced
> >  by a simple * (int64_t) ?
> 
> Clipping is required (absence leads to all tests failure).

Didnt you say in the other mail that mul_24_15() doesnt need any cliping ?


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

Many that live deserve death. And some that die deserve life. Can you give
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