[FFmpeg-devel] [RFC] TwinVQ decoder

[Vitor Sessak]

Kostya wrote:
> On Sat, Mar 07, 2009 at 05:47:51PM +0100, Vitor Sessak wrote:
>> Hi,
>>
>> This codec has some interesting features. It looks like whoever designed
>> it wanted to improve quality/bitrate, no matter if it add to ugliness or
>> file size. So they have a different set of codebooks for each possible
>> combination of frame_type, sample rate and bit rate (what makes for a
>> 370kb stripped object file).
>>
>> This code is still not review-quality, but any comment is welcome.
>>
>> -Vitor
> 
> [...]
>> static void mulddd(int cont, const float *buf1, const float *buf2, float *buf3)
>> {
>>     while(cont--)
>>         *buf3++ = (*buf1++)*(*buf2++);
>> }
>>
>> static void muldddre(int cont, const float *buf1, const float *buf2, float *buf3)
>> {
>>     while(cont--)
>>         *buf3++ = (*buf1++)*(*buf2--);
>> }
>>
>> static void addddd(int cont, const float *buf1, const float *buf2, float *buf3)
>> {
>>     while(cont--)
>>         *buf3++ = *buf1++ + *buf2++;
>> }
> 
> You should use dsputil functions instead of those if possible
> (i.e. no align problems)

I'll look into it. What I find a bit surprising, is that there is no 
equivalent to mulddd() in DSPutils, only the following:

      while(cont--)
          *buf2++ *= (*buf1++);


> [...] 
>> static void lsptowts(const float *a1, float *a2, TwinContext *tctx)
>> {
>>     float cos_vals[21];
>>     int i,j;
>>     const ModeTab *mtab = tctx->mtab;
>>     int n_fr_s = mtab->n_fr / mtab->fmode[FT_SHORT].sub;
>>     int mag_95 = 2 * mtab->fmode[FT_SHORT].sub;
>>     float *cos_TT = ff_cos_tabs[av_log2(mtab->n_fr)-1];
>>
>>     for (i=0; i < mtab->n_pr; i++)
>>         cos_vals[i] = 2*cos(a1[1+i]);
>>
>>     for (i=0; i < (n_fr_s/2); i++) {
>>         float st0=1., st1=1., st2=1., st3=1.;
>>
>>         for (j=0; j < mtab->n_pr; j += 2) {
>>             st0 *= 2*cos_TT[mag_95*(2*i+1)] + cos_vals[j+1];
>>             st1 *= 2*cos_TT[mag_95*(2*i+1)] - cos_vals[j+0];
>>             st2 *= 2*cos_TT[mag_95*(2*i+1)] + cos_vals[j+0];
>>             st3 *= 2*cos_TT[mag_95*(2*i+1)] - cos_vals[j+1];
>>         }
>>
>>         a2[i]         =st3*st3 + st1*st1 + (st1*st1 - st3*st3)*cos_TT[mag_95*(2*i+1)];
>>         a2[n_fr_s-i-1]=st0*st0 + st2*st2 + (st0*st0 - st2*st2)*cos_TT[mag_95*(2*i+1)];
>>     }
>> }
> 
> I also suspect some of CELP functions can be used instead.

Thanks for the tip. Also, if any audio codec expert find other functions 
already implemented somewhere else in FFmpeg, it would be very 
appreciated...

> Also Diego-like person may complain about mix of CamelCased and
> not_camel_cased function names not being very consistent.

I'll fix it before review. I have yet to find nice names to a lot of 
functions/vars...

> And for the rest of it: yay! Another unknown codec REd :)

;)

-Vitor