A2V2A-dither.py

#### BEGINNING OF LICENSE TEXT ####

## Copyright 2021 multiplealiases

## Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

## The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#### END OF LICENSE TEXT ####

import subprocess
import sys
import os
import shutil

## This script requires FFmpeg and SoX to be installed somewhere in PATH.
## If editing, you MUST encase all parameters in quotes, including the numbers.
## No error-correction done on variables; the whole script expects string type.
## You will need at least 2.5 times the size of the original audio file free on disk. Be warned!

print(sys.argv)

## Prints a suitable error and exits if at least one dependency of this script is nonexistent. This does not check for correctness.

if shutil.which("ffmpeg") == None and shutil.which("sox") == None:
    print ("Both FFmpeg and SoX are not installed on this system. Please install both to run this script.")
    sys.exit()
    
elif shutil.which("ffmpeg") == None:
    print("FFmpeg is not installed on this system. Please install it to run this script.")
    sys.exit()

elif shutil.which("sox") == None:
    print("SoX is not installed on this system. Please install it to run this script.")
    sys.exit()

## Prints usage information if given no parameters.
if len(sys.argv) == 1:
    print(f"Usage: {os.path.basename(__file__)} [sample rate] [no. of channels] [filename w/ extension] [video codec] [bitrate] [internal resolution] \n")
    sys.exit()


## Variables

#### Step 1
## Setting bit_depth to anything other than 8 will likely lead to severely-distorted audio. You have been warned!
bit_depth = "8"
sample_rate = sys.argv[1]
## Theoretically-changeable, but SoX will not allow signed 8-bit PCM as output.
encoding = "unsigned-integer"

## Compander parameters. 

## Compander definition. Defined from left-to-right.
dB_list = [(-80.0,-46.86), (-79.02,-45.89), (-77.99,-44.88), (-77.02,-43.92), (-76.03,-42.95), (-75.04,-41.98),
 (-74.02,-40.99), (-73.0,-39.98), (-72.01,-39.02), (-71.0,-38.05), (-70.01,-37.09),
 (-69.0,-36.12), (-68.0,-35.17), (-67.01,-34.23), (-66.0,-33.28), (-65.01,-32.34),
 (-64.0,-31.4), (-63.0,-30.48), (-62.0,-29.56), (-61.0,-28.65), (-60.0,-27.75),
 (-59.0,-26.86), (-58.0,-25.98), (-57.0,-25.12), (-56.0,-24.26), (-55.0,-23.42),
 (-54.0,-22.6), (-53.0,-21.78), (-52.0,-20.98), (-51.0,-20.2), (-50.0,-19.44),
 (-49.0,-18.7), (-48.0,-17.97), (-47.0,-17.26), (-46.0,-16.57), (-45.0,-15.9),
 (-44.0,-15.24), (-43.0,-14.61), (-42.0,-14.0), (-41.0,-13.4), (-40.0,-12.82),
 (-39.0,-12.27), (-38.0,-11.72), (-37.0,-11.2), (-36.0,-10.7), (-35.0,-10.21),
 (-34.0,-9.74), (-33.0,-9.29), (-32.0,-8.85), (-31.0,-8.42), (-30.0,-8.01),
 (-29.0,-7.61), (-28.0,-7.23), (-27.0,-6.86), (-26.0,-6.5), (-25.0,-6.15),
 (-24.0,-5.82), (-23.0,-5.49), (-22.0,-5.17), (-21.0,-4.87), (-20.0,-4.57),
 (-19.0,-4.28), (-18.0,-4.0), (-17.0,-3.72), (-16.0,-3.46), (-15.0,-3.2),
 (-14.0,-2.95), (-13.0,-2.7), (-12.0,-2.46), (-11.0,-2.23), (-10.0,-2.01),
 (-9.0,-1.78), (-8.0,-1.57), (-7.0,-1.36), (-6.0,-1.15), (-5.0,-0.95),
 (-4.0,-0.75), (-3.0,-0.56), (-2.0,-0.37), (-1.0,-0.18), (0.0,0.0)]

## Using list comprehension to convert the compander list into a more natural format for later.
x_dB = [x for x,y in dB_list]
y_dB = [y for x,y in dB_list]

## Declares strings. 
compress_dB = ""
expand_dB = ""

## Writes the compander lists into a format that SoX will understand.
for i in range(0,len(x_dB)):
    if i == (len(x_dB) - 1):
        compress_dB +=f"{x_dB[i]},{y_dB[i]}"
        expand_dB += f"{y_dB[i]},{x_dB[i]}"
    else:
        compress_dB += f"{x_dB[i]},{y_dB[i]},"
        expand_dB += f"{y_dB[i]},{x_dB[i]},"

## Attack, release and delay defined here for ease of change.
## I don't believe it's beneficial for a mu-law compander, but you are free to change this as you please.
attack = "0"
release = "0"
delay = "0"
knee_dB = "0.2"

## Companders tend to clip the output; this lowers the gain to prevent that. 
## Please note that audio is normalized after companding, so it's of little consequence.
out_gain_dB = "-12"
## Output still tends to clip, so a separate normalizing gain is needed.
norm_step1_gain = "-1.1"

#### Step 2
in_filename = os.path.splitext(sys.argv[3])[0]
in_extension = os.path.splitext(sys.argv[3])[1]

step2_out_extension = ".mkv"
resolution = sys.argv[6]
framerate = "30"
pixel_format = "rgb24"
video_codec = sys.argv[4]
bitrate_codec = sys.argv[5]

#### Step 3
# (no new variables; all recycled from Step 2)

#### Step 4.
## File-specific parameters. Set these equal to the original audio's settings.
channels = sys.argv[2]

## Final audio codec.
out_audio_codec = ".flac"
out_bit_depth = "24"

## Final maximum amplitude.
gain_dB = "-0.1"

## Combined variables. Used for brevity.
compress_atk_release = f"{attack},{release}"
compress_start_end = f"{knee_dB}:{compress_dB}"
expand_atk_release = f"{attack},{release}"
expand_start_end = f"{knee_dB}:{expand_dB}"

in_file = f"{in_filename}{in_extension}"
step1_out = f"{in_filename}-step1-compressed"
step2_out = f"{in_filename}-step2-{video_codec}-{bitrate_codec}-{resolution}"
step3_out = f"{in_filename}-step3-{video_codec}-{bitrate_codec}-{resolution}"
step4_out = f"{in_filename}-end-{video_codec}-{bitrate_codec}-{resolution}"

## Step 1: Compresses (in the audio engineering sense, not the computing sense), then normalizes an input audio file.
## Saves it as 8-bit PCM. Compression here prevents the -48 dB noise floor inherent in 8-bit PCM from interfering with the output later.
step1_list = ["sox",in_file,"--multi-threaded","--buffer","131072",
"-r",sample_rate,"-e",encoding,"-SV","-b",bit_depth,"-c",channels,f"{step1_out}.raw",
"compand",compress_atk_release,compress_start_end,out_gain_dB,"0",delay,"gain","-n",norm_step1_gain,"dither"]
print(step1_list)
subprocess.run(step1_list)

## Step 2: Takes in the 8-bit PCM as RGB 24-bit video (by default), and encodes it into a format of your choice as defined in the input parameters.
step2_list = ["ffmpeg","-y",
              "-f","rawvideo","-s",resolution,"-r",framerate,"-pix_fmt",pixel_format,"-i",f"{step1_out}.raw",
              "-c:v",video_codec,"-b:v",bitrate_codec,f"{step2_out}{step2_out_extension}"]
print(step2_list)
subprocess.run(step2_list)


## Step 3: Decode the encoded "video" back into raw video.
step3_list = ["ffmpeg","-y",
              "-i",f"{step2_out}{step2_out_extension}",
              "-f","rawvideo","-r",framerate,"-pix_fmt",pixel_format,f"{step3_out}.raw"]
print(step3_list)
subprocess.run(step3_list)

## Step 4: Use SoX to interpret our raw video back into 8-bit PCM.
## Expands the audio, re-gains it, and spits out the same format as the input.
step4_list = ["sox","--multi-threaded","--buffer","131072",
"-r",sample_rate,"-e",encoding,"-SV","-b",bit_depth,"-c",channels,f"{step3_out}.raw","-b",out_bit_depth,"-c",channels,f"{step4_out}{out_audio_codec}","compand",expand_atk_release,expand_start_end,out_gain_dB,"0",delay,"gain","-n",gain_dB]
print(step4_list)
subprocess.run(step4_list)