Merging .au files without the project file

Programming and Development Macros and Scripting
1

Hello,

I have a bunch of .au-files linked to an Audacity project, but I don’t have the project file itself. Luckily, the files can be sorted by creation date (the left and right mono files are created at the same time as a pair, I guess). I wrote a python script to rename the files according to their creation date, let Audacity convert them to mp3, then used ffmpeg -filter_complex amix=inputs=2:duration=longest to merge the two monos into one and then ffmpeg -i “concat:…|…|…” to append them all to one file. You can hear distinct cut-noises after each file, though. Any tips on how to do this right?

2

You can hear distinct cut-noises after each file, though.

You mean after each 6-second snippet? That could be your process getting the Left and Right wrong way around.

Audacity convert them to mp3,

Never use MP3 anywhere in a production process. It creates sound damage and has badly defined stop and start points. Try WAV 16-bit 44100.

I wrote a python script

What’s the possibility of publishing that script?

Koz

3

Yeah, using a different format did solve the problem. ffmpeg doesn’t support concatenating wav files though, so I converted au to mpeg (2x mono) to mpeg (1x mono) to mp3. That works okay. Here’s the code:

import os
from tkinter import filedialog
import subprocess

ffmpegPath = input("Where is ffmpeg.exe located? Press Enter if it's added to PATH, otherwise"\
                   " enter the full path to the executable.\n>> ")
if ffmpegPath == "\n":
    ffmpegPath = "ffmpeg"

#Search for the au files and 
auFolder = filedialog.askdirectory() +"/"
files = [auFolder+file for file in os.listdir(auFolder) if file.endswith(".au")]
#sort them by creation time
files = sorted(files, key=lambda file: os.stat(file).st_mtime)

#rename them according to creation time, so audacity conversion can't mess them up
i = 0
while i <= len(files)-2:
    try:
        os.rename(files[i], auFolder+str(i+1)+".au")
        os.rename(files[i+1], auFolder+str(i+2)+".au")
    except FileExistsError:
        break #This script apparently has already been run once
    i += 2
    
input("Now convert everything in " + auFolder + " to wav using audacity and press enter.\n"\
      "Use File-Apply Chain... for this (preferably wav format)")

#Convert the mono canals into one
files = [auFolder+"cleaned/"+file for file in os.listdir(auFolder+"cleaned/")]
files = sorted(files, key=lambda file: int(file.split("/")[-1][:-4]))
try:
    os.mkdir("converted")
except FileExistsError:
    for file in os.listdir("converted"):
        os.remove("converted/"+file)
i = 0
while i <= len(files)-2:
    subprocess.run(ffmpegPath+" -i \""+files[i]+"\" -i \""+files[i+1] +\
                   "\" -filter_complex amix=inputs=2:duration=longest -y converted/"+str(i)+".mpeg")
    i += 2
    
#concatenate with the created files
files = ["converted/"+file for file in os.listdir("converted/")]
files = sorted(files, key=lambda file: int(file.split("/")[-1][:-5]))
command = ffmpegPath+" -i concat:\""
for i in range(len(files)):
    if i == len(files)-1:
        command += files[i]+"\" "
    else:
        command += files[i]+"|"

command += " -y converted.mp3"
#The file is created where this script is run
subprocess.run(command)

Thanks!

4

SoX does. http://sox.sourceforge.net/

5

Obviuosly it has to be

if ffmpegPath == "":
    ffmpegPath = "ffmpeg"

instead. But I can’t edit my post or sent a pm to anybody. So that’s neat.