[FFmpeg-devel] [PATCH] Common ACELP code & G.729 [3/7] - vectors operations

[Vladimir Voroshilov]

2008/5/22, Michael Niedermayer <michaelni at gmx.at>:
> On Thu, May 22, 2008 at 05:50:28PM +0700, Vladimir Voroshilov wrote:

[...]

>  > >> +void ff_acelp_fc_enchance_harmonics(
>  > >> +        int16_t* fc_v,
>  > >> +        int pitch_delay,
>  > >> +        int16_t gain_pitch,
>  > >> +        int length)
>  > >> +{
>  > >> +    int i;
>  > >> +
>  > >> +    for(i=pitch_delay; i<length;i++)
>  > >> +        fc_v[i] += (fc_v[i - pitch_delay] * gain_pitch) >> 14;
>  > >> +}
>  > >> +
>  > >> +void ff_acelp_build_excitation(
>  > >> +        int16_t* exc,
>  > >> +        const int16_t *ac_v,
>  > >> +        const int16_t *fc_v,
>  > >> +        int16_t gp,
>  > >> +        int16_t gc,
>  > >> +        int subframe_size)
>  > >> +{
>  > >> +    int i;
>  > >> +
>  > >> +    // Clipping required here; breaks OVERFLOW test.
>  > >> +    for(i=0; i<subframe_size; i++)
>  > >> +        exc[i] = av_clip_int16((ac_v[i] * gp + fc_v[i] * gc + 0x2000) >> 14);
>  > >> +}
>  > >
>  > > duplicate, these 2 functions do the same, that is a wheighted sum of 2
>  > > vectors.
>  > >
>  >
>  > agree.
>  > As i see
>  >
>  > ff_acelp_fc_enchance_harmonics(fc_v, pitch_delay, gain_pitch, length)
>  >
>  > is equal to
>  >
>  > ff_acelp_build_excitation(fc_v+pitch_delay, fc_v+pitch_delay,
>  > fc,1<<14, gain_pitch, length-pitch_delay);
>  >
>  > but what should i do with rounding ?
>  >
>  > what about adding additional parameter (const summand) to
>  > ff_acelp_build_excitation
>  > I.e. something like:
>  >
>  > void ff_acelp_build_excitation(
>  >         int16_t* exc,
>  >         const int16_t *ac_v,
>  >         const int16_t *fc_v,
>  >         int16_t gp,
>  >         int16_t gc,
>  >         int16_t summand,
>  >         int subframe_size)
>  > {
>  >     int i;
>  >
>  >     // Clipping required here; breaks OVERFLOW test.
>  >     for(i=0; i<subframe_size; i++)
>  >         exc[i] = av_clip_int16((ac_v[i] * gp + fc_v[i] * gc + summand) >> 14);
>  > }
>  >
>  > What about renaming ff_acelp_build_excitation like ff_acelp_weighted_vector_sum
>  > (and subframe_size -> length, ac_v -> vect_a, fc_v -> vect_b, gc ->
>  > weight_coeff_a, gp -> weight_coeff_b)?
>
>
> ok
>
>
>
>  >
>  > P.S. "summand" don't look like the best name too.
>
>
> maybe offset or rounder are better?
>

here is the patch.
I have also added "shift" parameter.
This will simplify reusing from g729 postfilter (since it
uses vectors with different fixed-point base).


-- 
Regards,
Vladimir Voroshilov     mailto:voroshil at gmail.com
JID: voroshil at gmail.com, voroshil at jabber.ru
ICQ: 95587719
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