[MPlayer-dev-eng] [RFC] HRTF filter revision

[Yue Shi Lai]

Hi,

Attached is a snapshot of what I would like to propose as a revised HRTF 
filter. I would appreciate any comment or criticism.

I believe that the current version already surpasses the previous 
implementation in that:

- The room acoustics up to ~ 50 ms can be modeled, this allows the 
channels to be further moved "out of the head".

- The equalization can be performed at run time, and is therefore more 
rigorous.

There are a few things that still needs to be done:

- Reimplement support for 2 channel matrix coded signal

- Implement larger rooms with speakers attached to the wall.

- Take reverberation into account when equalize (for a correct overall 
gain).

- Use FFT as alternative (unknown if potentially faster).

I saw that foobar2000 has a filter (no source code) that links to 
DolbyHph.dll (Dolby Headphone filter bundled with some Windows DVD 
players). I managed so far to write a Wine code that does the same. This 
may allow a direct comparison of the acoustics soon.

A question: What is the state of libavcodec/avfft.c? The last time I 
checked, it segfaults (on x86_64) whenever I try to av_fft_permute().

Best,

Yue Shi Lai
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