[FFmpeg-devel] [PATCH] Simplify IMDCT in dca.c

[Alexander E. Patrakov]

I wrote:

> Property (3) works, and that's how I extracted h(n) from the "black box"
> response.

What I did check is:

resp[i] / resp0[i] == sign * cos((b + 0.5) * x) / cos(0.5 * x) for all
bands, and I calculated h[i] as resp0[i] / cos(0.5 * x)

where sign is +1 or -1, b is the band number, i runs from 0 to 511, and x ==
M_PI * (i + 16.5) / 32, resp is the 512-sample black box response to "1 in
i-th band, followed by 31 all-zero samples", resp0 is the analogous
response to 0-th band.

-- 
Alexander E. Patrakov