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

[Michael Niedermayer]

On Sat, Nov 07, 2009 at 12:03:39AM +0100, Vitor Sessak wrote:
> Michael Niedermayer wrote:
>> 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)
>
> Since pa[] is an array not a pointer I cannot do the while(lp_half_order--) 
> { (...) pa++; ga++; lpc++; lpc2--;} trick not to use the var "i" (and the 
> other option would use lpc[int8_var]). In this new version I've also made 
> the loop count forward to make it more readable.

you could change lp_half_order back to int if reynaldo doesnt mind.
i think that would avoid the problem?

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

> ... defining _GNU_SOURCE...
For the love of all that is holy, and some that is not, don't do that.
-- Luca & Mans
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