syncstart 1.1.1

Description:

syncstart 1.1.1

SYNOPSIS
Command line help:
usage: syncstart [-h] [--version] [-v] [-b BEGIN] [-t TAKE] [-n] [-d] [-l LOWPASS] [-c] [-s] [-q] in1 in2

CLI interface to sync two media files using their audio or video streams.
ffmpeg needs to be available.


positional arguments:
in1 First media file to sync with second.
in2 Second media file to sync with first.

options:
-h, --help show this help message and exit
--version show program's version number and exit
-v, --video Compare video streams. (audio is default)
-b BEGIN, --begin BEGIN
Begin comparison X seconds into the inputs. (default: 0)
-t TAKE, --take TAKE Take X seconds of the inputs to look at. (default: 20)
-n, --normalize Normalizes audio/video values from each stream.
-d, --denoise Reduces audio/video noise in each stream.
-l LOWPASS, --lowpass LOWPASS
Audio option: Discards frequencies above the specified Hz, e.g., 300. 0 == off (default)
-c, --crop Video option: Crop to 4:3. Helpful when aspect ratios differ.
-s, --show Suppress "show diagrams", in case you are confident.
-q, --quiet Suppresses standard output except for the CSV result. Output will be:
file_to_advance,seconds_to_advance


DESCRIPTION
The steps taken by syncstart:

get the maximum audio sample frequency or video frame rate among the inputs using ffprobe
process and extract sample audio/video clips using ffmpeg with some default and optional filters
read the two clips into a 1D array and apply optional z-score normalization
compute offset via correlation using scipy ifft/fft
print ffmpeg/ffprobe output or optionally quiet that
show diagrams to allow MANUAL correction using ZOOM or optionally suppress that
print result

MANUAL correction with ZOOM:

at the checkbox on the top right check or uncheck to make the statement true
turn on ZOOM with the magnifying glass on the bottom left
draw a rectangle that stretches between two X that should coincide
(Y is not relevant but don’t make it 0)
read the final correction from the top right or in the final output

Requirements:

ffmpeg and ffprobe installed
Python3 with tk (tk is separate on Ubuntu: python3-tk)

References:

https://ffmpeg.org/ffmpeg-all.html
https://dsp.stackexchange.com/questions/736/how-do-i-implement-cross-correlation-to-prove-two-audio-files-are-similar
https://dsp.stackexchange.com/questions/18846/map-time-difference-between-two-similar-videos

Within Python:
from syncstart import file_offset


INSTALLATION
To install for user only, do:
pip install --user syncstart
Or activate a virtualenv and do:
pip install syncstart

EXAMPLES
# compute audio offset with default settings:
syncstart from_s10.m4a from_gopro.m4p

# compute audio offset using first 10 seconds with denoising, normalization and a 300 Hz lowpass filter:
syncstart video1.mp4 video2.mkv -t 10 -dnl 300

# compute video offset using first 20 seconds, don't show plots, only output final result:
syncstart video1.mp4 video2.mkv -vsq

# compute video offset using seconds 15 to 25 with denoising, cropping and normalization:
syncstart video1.mp4 video2.mkv -b 15 -t 10 -vdcn


License
MIT