Binaural virtual surround sound reproduction and surround sound stereo downmix.

Now able to take 7.1.4 Audio files as input for virtual surround.

• 7.1.4 layout: L, R, C, LFE, LS, RS, RLS, RRS, FLU, FRU, RLU, RRU
• HRIRs from database:
  • L: Elevation 0 degree, Azimuth -65 degree
  • R: Elevation 0 degree, Azimuth 65 degree
  • C: Elevation 0 degree, Azimuth 0 degree
  • LFE: N/A
  • LS: Elevation 180 degree, Azimuth -20 degree
  • RS: Elevation 180 degree, Azimuth 20 degree
  • RLS: Elevation 180 degree, Azimuth -55 degree
  • RRS: Elevation 180 degree, Azimuth 55 degree
  • FLU: Elevation 45 degree, Azimuth -30 degree
  • FRU: Elevation 45 degree, Azimuth 30 degree
  • RLU: Elevation 135 degree, Azimuth -30 degree
  • RRU: Elevation 135 degree, Azimuth 30 degree

From Soundly 5.0 Surround Sound library: https://getsoundly.com/
Content: Garage ambience with water dripping.

Processing:

1. Get HRIR from database for L, C, R, Ls, Rs.
   • L: Elevation 0 degree, Azimuth -30 degree
   • C: Elevation 0 degree, Azimuth 0 degree
   • R: Elevation 0 degree, Azimuth 30 degree
   • Ls: Elevation 180 degree, Azimuth -60 degree
   • Rs: Elevation 180 degree, Azimuth 60 degree
2. Convolve Each channel with respective HRIR.
   • Left ear signal = Original file * Left Ear HRIR
   • Right ear signal = Original file * Right Ear HRIR
3. Sum 5 left ear channel to one left channel, and 5 right ear channel to one right channel.
4. Combine left and right channel to stereo file.
5. Normalize: Normalize according to change in volume (ratio)
   • ratio: Original signal / Processed signal

Processing:

1. Left All: L + (–3 dB × C) + (–3 dB × Ls)
2. Right All: R + (–3 dB × C) + (–3 dB × Rs)
3. Normalize: Normalize according to change in volume (ratio)
   • ratio: Original signal / Processed signal

• HRTF data from CIPIC database by UC Davis: https://www.ece.ucdavis.edu/cipic/spatial-sound/hrtf-data/
• Stereo downmix method reference Dolby website (Lo/Ro - default): https://professionalsupport.dolby.com/s/article/How-do-the-5-1-and-Stereo-downmix-settings-work?language=en_US