[FFmpeg-devel] [PATCH] RDFT for Bink audio
Thu Jan 15 17:23:54 CET 2009
Alex Converse wrote:
>> Did you implement both modes in this patch ? To me it looks like we also
>> need a dct function also.
> Separate transform will be in a separate patch.
>> + ev.re = k1*(data[i1 ]+data[i2 ]);
>> + od.im = k2*(data[i1 ]-data[i2 ]);
>> + ev.im = k1*(data[i1+1]-data[i2+1]);
>> + od.re = -k2*(data[i1+1]+data[i2+1]);
>> + /* Apply twiddle factors to the odd FFT and add to the even FFT */
>> + data[i1 ] = ev.re + od.re*tcos[i] - od.im*tsin[i];
>> + data[i1+1] = ev.im + od.im*tcos[i] + od.re*tsin[i];
>> + data[i2 ] = ev.re - od.re*tcos[i] + od.im*tsin[i];
>> + data[i2+1] = -ev.im + od.im*tcos[i] + od.re*tsin[i];
>> That part of the code looked like some code we have in the qdm2.c
>> decoder ? Can you look and see if it matches? I have always wondered
>> what kind of transform it was.
> It is clearly a IRDFT with something weird going on with the 0 and N/2
> points. Do you know anything about the genesis of that code that isn't
> in your pdf? The n2 term is clearly not passed to the FFT at all.
Sorry no, this is what we have. It is possible it is not correct. I
guess we could at least add a comment to the code now that we know what
>> Code wise other then some strange indentation in the struct it looked ok.
> Some tabs crept in, try this.
Looks ok to me.
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