Input: a stereo audio file (L+R)
Output: a 6-channel audio file in 5.1(side) layout (FL+FR+FC+LFE+SL+SR)
This is a simplified process, using just sox command line, to generate a 5.1 audio file.
Step 1: Front left & right channel
- we just copy the left and right channel into the first two channels FR + FL.
sox input.wav temp_flfr.wav - Optionally, we could normalize the volume, use 24 bit sampling at 48KHz
sox input.wav temp_flfr.wav -b 24 -r 48000 gain -n -3(normalize to -3 dB)
Step 2: LFE channel (Low frequency/subwoofer)
- we take only the frequencies under 120 Hz for the subwoofer
sox temp_flfr.wav temp_lfr.wav remix 1,2 lowpass 120
Step 3: center channel (voice)
- there are sophisticated ways to take only the voice out of a recording, but since we only have sox at our disposal, we will just filter out the human voice frequencies 300-3500 Hz
sox temp_flfr.wav temp_c.wav remix 1,2 highpass 300 lowpass 3500
Step 4: surround channels
- the simplest solution is to just use the L+R input but less loud
sox temp_flfr.wav temp_slsr.wav gain -6 - a more sophisticated version would use a bit of the ‘oops’ effect and add some delay
sox temp_flfr.wav temp_slsr.wav remix 1v-0.8718,2v0.4898 1v0.4898,2v-0.8718 delay 0.15
Step 5: merge all channels together
- sox has a very simple merge syntax
sox -M temp_flfr.wav temp_c.wav temp_lfr.wav temp_slsr.wav output51.wav
Inspiration: forum.videohelp.com