How to synchronize audio and video stream from different sources exactly in [ms]?

Expected Behavior

Receive synchronized video clip (accuracy in ms).

Actual Behavior

Unsynchron video clips:

• first try: audio 1.5 s late
• 2nd try: audio 2.5 s late

Steps to Reproduce the Problem

from moviepy.editor import VideoFileClip, AudioFileClip

VIDEOFILE = 'video_with_good_quality.mp4'
AUDIOFILE = 'video_with_origin_language.mp4'
OUTPUTFILE = 'video_with_good_quality+origin_language.mp4'
TEST_DURATION = 215.0 # sec
AUDIO_DELAY = -1.5


# from audio attribute of the VideoFileClip object
audio2 = VideoFileClip(AUDIOFILE).audio
# video including original audio
video_a = VideoFileClip(VIDEOFILE)

#create test clips (short)
# FIRST TRY (without delay correction)
audio2_test = audio2.subclip(t_start=audio2.duration-TEST_DURATION, t_end=audio2.duration)
video_a_test = video_a.subclip(t_start=video_a.duration-TEST_DURATION, t_end=video_a.duration)

# combine test clips
video_va_a2 = video_a_test.set_audio(audio2_test)

# show
video_va_a2.ipython_display(maxduration=250, width=640)

#video_a_test.ipython_display(maxduration=250, width=640)  # proofed, but not synchronized: audio -1500 ms to correct

# close all instances
audio2.close()
video_a.close()

With mpv video player I found out that the audio stream is 1500 ms late. This was OK, because it was only a guess to get a synchonized file. Thus, I introduced a correction factor AUDIO_DELAY = -1.5 in [s]. to create the test clips:

# 2nd try (with delay correction)
audio2_test = audio2.subclip(t_start=audio2.duration-TEST_DURATION+AUDIO_DELAY, t_end=audio2.duration+AUDIO_DELAY)
video_a_test = video_a.subclip(t_start=video_a.duration-TEST_DURATION, t_end=video_a.duration)

Specifications

• Python Version: 3.8
• Moviepy Version: 1.0.2
• Platform Name: Linux Mint Mate
• Platform Version: 19.3

[spfeifer222]

Yes, but it’s a negative value. It’s Mathematical correct, isn’t it? However, I tried to use a posive value, but failed.

1 file is uploaded, but the second need about 30 min to finish.

[Josep-DA]

Thanks. This worked out for me.