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bartolsthoorn / NVDSP

iOS/OSX DSP for audio (with Novocaine)
MIT License
415 stars 79 forks source link

Digital Room Correction #5

Open neox38 opened 10 years ago

neox38 commented 10 years ago

Any idea on how complicated it would be to add support for digital room correction filter. http://en.wikipedia.org/wiki/Digital_room_correction

Also how about a decay filter?

bartolsthoorn commented 10 years ago

To do digital room correction you should first know how to simulate rooms. By placing a microphone in a room and recording the response of a sine sweep you can get the response for every frequency. When you have a dry signal you can multiply it by a recorded impulse response of any room to make it sound as if it was playing in that room. To do the opposite you record the impulse response of a room and inverse it remove the effect of an already 'wet' track.

NVDSP currently only does filtering using a biquad filter. There's no code doing impulse reponse, although that would be rad!

Apple Logic has an app bundled called 'Impulse Response', looking it up on youtube will probably help you understand the subject. There are also VSTs (software used by producers and artists) entirely based on simulation rooms, like Altiverb I think they also describe a little bit of the process in their promo video. Once you are able to simulate rooms I think inversing it will be not so hard.