[FFmpeg-devel] Make ff_acelp_lsp2lpc() more generic

[Måns Rullgård]

Mohamed Naufal <naufal11 at gmail.com> writes:

> Hi
>
> The attached patch allows using the function by both G.729 & G.723.1.
>
> -void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
> +void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order, int shift, int rounder, int sign)
>  {
>      int i;
>      int f1[lp_half_order+1]; // (3.22)
> @@ -103,9 +103,10 @@ void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order)
>          int ff1 = f1[i] + f1[i-1]; // (3.22)
>          int ff2 = f2[i] - f2[i-1]; // (3.22)
>  
> -        ff1 += 1 << 10; // for rounding
> -        lp[i]    = (ff1 + ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
> -        lp[(lp_half_order << 1) + 1 - i] = (ff1 - ff2) >> 11; // divide by 2 and (3.22) -> (3.12)
> +        ff1 += rounder; // for rounding
> +        // divide by 2 and scale
> +        lp[i]    = av_clip_int16(sign * av_clip_int16((ff1 + ff2) >> (shift + 1)));
> +        lp[(lp_half_order << 1) + 1 - i] = av_clip_int16(sign * av_clip_int16((ff1 - ff2) >> (shift + 1)));

That clipping will probably have a severe performance impact.  Did you
benchmark this?

-- 
M?ns Rullg?rd
mans at mansr.com