[FFmpeg-devel] [PATCH] RDFT for Bink audio
Thu Jan 15 10:25:52 CET 2009
Alex Converse wrote:
> Attached is an implementation of the Real Discrete Fourier Transform as
> required for Bink Audio.
> Alex Converse
Hi, Bink audio has 2 modes:
+ if (s->use_dct)
+ ff_dct_calc (&s->trans.dct, coeffs);
+ ff_rdft_calc(&s->trans.rdft, coeffs);
Did you implement both modes in this patch ? To me it looks like we also
need a dct function also.
+ 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.
Code wise other then some strange indentation in the struct it looked ok.
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