[FFmpeg-devel] [PATCH] do not hardcode filter order in ff_acelp_lspd2lpc()

[Michael Niedermayer]

On Thu, Nov 05, 2009 at 05:36:36AM +0100, Vitor Sessak wrote:
> Reynaldo H. Verdejo Pinochet wrote:
>> Hello Vitor
>> Vitor Sessak wrote:
>>> $subj. It is useful for SIPR but also it makes sense to make shared
>>> functions as general as possible.
>> QCELP part is ok but I'd make lp_half_order
>> a single-byte sized type.
>
> Fine for me (I suppose comparing uint8_t with int is not slower in any arch 
> we support). New version attached.
>
> -Vitor

>  lsp.c      |   12 ++++++------
>  lsp.h      |    2 +-
>  qcelpdec.c |    2 +-
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 4c16615dbbd30c5ab006c8da8b879ea577097b39  lspd2lpc_2.diff
> Index: libavcodec/lsp.c
> ===================================================================
> --- libavcodec/lsp.c	(revision 20450)
> +++ libavcodec/lsp.c	(working copy)
> @@ -155,20 +155,20 @@
>      }
>  }
>  
> -void ff_acelp_lspd2lpc(const double *lsp, float *lpc)
> +void ff_acelp_lspd2lpc(const double *lsp, float *lpc, uint8_t lp_half_order)
>  {
> -    double pa[6], qa[6];
> +    double pa[lp_half_order+1], qa[lp_half_order+1];
>      int   i;
>  
> -    lsp2polyf(lsp,     pa, 5);
> -    lsp2polyf(lsp + 1, qa, 5);
> +    lsp2polyf(lsp,     pa, lp_half_order);
> +    lsp2polyf(lsp + 1, qa, lp_half_order);
>  
> -    for (i=4; i>=0; i--)
> +    for (i=lp_half_order-1; i>=0; i--)
>      {
>          double paf = pa[i+1] + pa[i];
>          double qaf = qa[i+1] - qa[i];
>  
>          lpc[i  ] = 0.5*(paf+qaf);
> -        lpc[9-i] = 0.5*(paf-qaf);
> +        lpc[(lp_half_order << 1) - 1 -i] = 0.5*(paf-qaf);
>      }

i would
lpc2= lpc + (lp_half_order << 1) - 1;
and
lpc2[-i] = ...

that way lp_half_order and i also become redundant and one can be droped
about int8 vs. int, its possible that using int8 as index into an array
like lpc[int8_variable] could be slower in some archs (x86 being one)

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

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20091106/adcb0cc2/attachment.pgp>