to_wav.sh

#!/bin/bash

# Set the number of parallel processes
NUM_PROCESSES=16

# Create the wav directory if it doesn't exist
mkdir -p wav

# Function to convert a single file
convert_file() {
  local opus_file="$1"
  local wav_file=$(echo "$opus_file" | sed 's|opus/|wav/|; s|\.opus$|\.wav|')
  
  # Create the subdirectory in wav/ if it doesn't exist
  mkdir -p "$(dirname "$wav_file")"
  
  # Use the line below to keep the original sample rate 48kHz
  # ffmpeg -i "$opus_file" "$wav_file" -loglevel error
  # Or change the -ar 16000 to other sample rates
  ffmpeg -i "$opus_file" -ar 16000 "$wav_file" -loglevel error
  
  echo "Converted: $opus_file -> $wav_file"
}

export -f convert_file

# Find all .opus files and process them in parallel
find opus/ -name "*.opus" -print0 | xargs -0 -P "$NUM_PROCESSES" -I{} bash -c 'convert_file "$@"' _ {}

echo "Conversion complete."