[FFmpeg-devel] [PATCH] WMA Voice postfilter

[Michael Niedermayer]

On Sun, Apr 11, 2010 at 07:48:07PM -0400, Vitor Sessak wrote:
> Ronald S. Bultje wrote:
>> Hi,
>> On Thu, Apr 1, 2010 at 11:52 AM, Reimar D?ffinger
>> <Reimar.Doeffinger at gmx.de> wrote:
>>> On Thu, Apr 01, 2010 at 11:25:25AM -0400, Ronald S. Bultje wrote:
>>>> I'm probably asking silly questions here, but can I allocate aligned
>>>> memory on the stack? Or do they have to be in the struct?
>>> You better avoid it on the stack, it won't work reliably on all
>>> supported configurations.
>> Thanks for the advice, this patch is tested with yasm and does not
>> crash, so I think alignment is OK now. By putting synth buffer in the
>> context, I was also able to remove one memcpy(). (One or two more of
>> those are possible in the original code, previously already suggested
>> by Vitor, so I might go ahead and do that in a future patch also.)
>
> Some comments:
>
>> +static int kalman_smoothen(WMAVoiceContext *s, int pitch,
>> +                           const float *in, float *out, int size)
>> +{
>> +    int n;
>> +    float optimal_gain = 0, dot;
>> +    const float *ptr = &in[-FFMAX(s->min_pitch_val, pitch - 3)],
>> +                *end = &in[-FFMIN(s->max_pitch_val, pitch + 3)],
>> +                *best_hist_ptr;
>> +
>> +    /* find best fitting point in history */
>> +    do {
>> +        dot = ff_dot_productf(in, ptr, size);
>> +        if (dot > optimal_gain) {
>> +            optimal_gain  = dot;
>> +            best_hist_ptr = ptr;
>> +        }
>> +    } while (--ptr >= end);
>> +
>> +    if (optimal_gain <= 0)
>> +        return -1;
>> +    dot = ff_dot_productf(best_hist_ptr, best_hist_ptr, size);
>> +    if (dot <= 0) // would be 1.0
>> +        return -1;
>> +
>> +    if (optimal_gain <= dot) {
>> +        dot = 0.5 / (0.5 + 0.3 * optimal_gain / dot); // 0.0625-1.0000
>
> This can be done with one less division:
>
> dot = (0.5 * dot) / (0.5 * dot + 0.3 * optimal_gain); // 0.0625-1.0000

and 2 lesss multiplications:
dot / (dot + 0.6 * optimal_gain);

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

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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