Simple automation in FFmpeg batch encoding

# FFmpeg batch conversion script
# Yunzhu Li

import os
import subprocess

# Convert a single file with FFmpeg
def ffmpeg_conv(file_in, file_out, crf=17, max_bitrate=None, start=None, length=None):

    ffmpeg_path = '/path/to/ffmpeg'
    cmd = [ffmpeg_path]

    # Input
    cmd.append('-i')
    cmd.append(file_in)

    # Video (x264)
    cmd.append('-c:v')
    cmd.append('libx264')

    cmd.append('-profile:v')
    cmd.append('high')

    cmd.append('-level')
    cmd.append('4.2')

    cmd.append('-crf')
    cmd.append(str(crf))

    # Limit maximum bit-rate
    if max_bitrate != None:
        cmd.append('-maxrate')
        cmd.append(str(max_bitrate) + 'M')

        cmd.append('-bufsize')
        cmd.append(str(max_bitrate * 10) + 'M')

    # Audio (AAC)
    cmd.append('-c:a')
    cmd.append('aac')

    # Copy subtitle stream
    cmd.append('-scodec')
    cmd.append('copy')

    # Add start time and length
    if start != None and length != None:
        cmd.append('-ss')
        cmd.append(start)
        cmd.append('-t')
        cmd.append(length)

    # Output path
    cmd.append(file_out)

    # Execute command
    process = subprocess.Popen(cmd)
    process.wait()


# Convert all files in a given directory recursively
def conv_path_recursive(path, crf=17, max_bitrate=None):
    for root, dirs, files in os.walk(path):
        for file_name in files:
            file_in  = root + '/' + file_name
            file_out = root + '/' + file_name + '.conv.mkv'
            ffmpeg_conv(file_in, file_out, crf, max_bitrate)

# Convert all files '/to/some/path' with crf=17 and 20Mbps max bit-rate.
conv_path_recursive('/to/some/path', 17, 20)

import os

path = '/to/some/path'

for root, dirs, files in os.walk(path):
    for file_name in files:
        if '.conv.mkv' in file_name:
            file_name_new = file_name.replace('.conv.mkv', '')
            os.rename(root + '/' + file_name, root + '/' + file_name_new)