[FFmpeg-devel] [PATCH] Common ACELP routines (2/3) - filters

[Michael Niedermayer]

On Fri, Apr 25, 2008 at 12:07:15AM +0700, Vladimir Voroshilov wrote:
> On Thu, Apr 24, 2008 at 10:13 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
[...]
> >  > > > +        filter_data[10+n] = out[n] = sum;
> >  > >
> >  > > This duplicated storeage is unacceptable.
> >  >
> >  > First for all assigned to filter data values will be used in loop later.
> >  > Thus filter_data can not be eliminated.
> >  > I can't use "out" instead of it due to necessary 10 items
> >  > with data from previous subframe at top).
> >  > Extending out with 10 items at top will require another temporary buffer
> >  > one memcpy somewhere later (because i will not be able to use output buffer
> >  > directly).
> >
> >  The double write is definitly useless after the first 10 iterations as
> >  after that you can just work in the out buffer.
> >
> >  foobar_filter(filter_data+10, 10);
> >  memcpy(out, filter_data+10, 10);
> >  foobar_filter(out+10, N-10);
> >
> >  should work fine and will for large N (dunno how large it is, so maybe
> >  this isnt worth it ...) be faster. Also it allows filter_data to be smaller.
> 
> ... and code will look like :(
> 
> if(foobar_filter(filter_data+10, 10)!=OVERFLOW)
> {
>   memcpy(out, filter_data+10, 10);
>   if(foobar_filter(out+10, N-10)==OVERFLOW)
>   {
>      for(i=0;i<len;i++) out>>=2;
>      foobar_filter(filter_data+10, 10);
>      memcpy(out, filter_data+10, 10);
>      foobar_filter(out+10, N-10);
>   }
> }
> else
> {
>      for(i=0;i<len;i++) out>>=2;
>      foobar_filter(filter_data+10, 10);
>      memcpy(out, filter_data+10, 10);
>      foobar_filter(out+10, N-10);
> }

for(;;){
    overflow= foobar_filter(filter_data+10, 10);
    memcpy(out, filter_data+10, 10);
    overflow|= foobar_filter(out+10, N-10);
    if(!overflow)
        break;
    for(i=0;i<len;i++) out>>=2;
}


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

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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