syncstart 1.1.1

Calculate the cut needed at start to sync two media files.

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