[FFmpeg-devel] [PATCH] Common ACELP code & G.729 [6/7] - G.729 postfilter

[Diego Biurrun]

On Sun, May 11, 2008 at 10:01:41PM +0700, Vladimir Voroshilov wrote:
> 
> --- /dev/null
> +++ b/libavcodec/g729postfilter.c
> @@ -0,0 +1,705 @@
> +
> +    /*
> +      4.2.1, Equation 79 Residual signal calculation
> +      ( filtering through A(z/FORMANT_PP_FACTOR_NUM) , one half of short-term filter)
> +    */

Stray space after the "("; this could be on just two lines.

> +        /*
> +          Compute denominator of pseudo-normalized correlation R'(0)
> +        */

.

> +        /*
> +          Compute signals with non-integer delay k (with 1/8 precision), where k is in [0;6] range.
> +          Entire delay is qual to best_delay+(k+1)/8
> +          This is archieved by applying an interpolation filter of legth 33
> +          to source signal.
> +        */


> +          Compute also maximum value of above denominators over all k.

Also compute

> +          Search is done in [int(T0)-1; intT(0)+1] range with 1/8 precision

.

> +                /*
> +                  Compute numerator of pseudo-normalized correlation R'(k)
> +                  (4.2.1, Equation 81)

.

> +          Recompute delayed signal with an interpolation filter of length 129

.

> +          Compute R'(k) correlation's numerator

.

> +          Compute R'(k) correlation's denominator

.

> +          Delayed signal will be selected if it increases R'(k)
> +          correlation

.

> +        //Checking if longer filter increases the values of R'(k)

Check, .

> +      Filtering through selected filter

filter

> + * \brief calculate reflection coefficient for tilt compensation filter (4.2.3)

Capitalize, add period.

> + * \remark routine also calculate
> + *         gain term for short-term filter (gf) and multiply speech
> + *         data by 1/gf

The routine also calculates the gain term for the short-term filter (gf)
and multiplies the speech data by 1/gf.

> + * \note all members of lp_gn, except 10-19 must be equal to zero

Capitalize, add period.

> + * \brief apply tilt compensation filter (4.2.3)

ditto

> +int16_t g729_adaptive_gain_control(int gain_before, int gain_after, int16_t *speech, int subframe_size, int16_t gain_prev)

That's a very long line..

> --- /dev/null
> +++ b/libavcodec/g729postfilter.h
> @@ -0,0 +1,119 @@
> +
> +/**
> + * Tilt compensation factor (G.729, k1>0)

lowercase, same below

> + * 1.0 / (1.0 + 0.5) in Q15
> + * where 0.5 is minimum value of

is the

> + * At second stage long-term postfilter searches best fractional pitch
> + * delay with 1/(1+ANALYZED_FRAC_DELAYS) resolution around found at first stage
> + * integer pitch delay.

Ummm, "around" what?

Diego