Virtual choirs allow people from across the world or just across town to collaborate and make music together. If you are an experienced creator, these tools can help your project come together more quickly. For those that are new, these tools can open the door to this fascinating world (without requiring audio or video editing experience or expensive software) so that you and your performers can show off your efforts and talents!
An online version of these tools is available here: https://virtualchoir.flightgear.org
- Record a reference track for your piece.
- Send this track to all participants with their part(s).
- Participants listen to the reference track through headphones, and then record themselves playing their part in sync with the reference track.
- Collect all the preformance tracks in a folder.
- The tools here will scan all the audio and video tracks in your project, then analyze and compare every track to every other track to find a best mutual syncronization (using math, frequencies, correlations, optimizations ... engineering stuff.)
- Next your audio tracks will get mixed together.
- Finally all your videos will be rendered in a simple gridded fashion to produce a virtual choir perfomance.
- In the first pass, these tools write out an audacity import file that lists all your tracks with the computed time offset. You can open audacity, import all the individual tracks (at the proper time offsets) and investigate which track(s) didn't sync, and manually adjust them. When it's just a track or two, this is really easy and quick. When you are happy with the manual adjustments, save your audacity project as a .aup file. You can sync videos this way too, by syncing their audio tracks in audacity (if they aren't already synced automatically in the first pass.)
- Run the program a 2nd time, but now we see the .aup file and read the time offsets out of that. Then the tracks are mixed and the gridded video is automatically rendered as before.
accompianment, or mute a voice that isn't working out?
- All this is possible by creating a 'hints.txt' file. Just list a file name along with the video rotation hint or audio gain hint, and rerun the program.
fixup work on the audio?
- We can write all the audio tracks back out with padding/trimming so they all align exactly at time zero. This lets you import all your tracks into your favorite DAW (digital audio workstation) software, but saves you the time of manually fixing the time syncronization for every track.
There are two sync strategies available.
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The wave samples of each track are correlated with every other track to find a best fit. The time offsets for all tracks relative to all the other tracks are compared against each other to produce a mutually optimal final sync. (The softwareis solving a big optimization problem to find the best mutual fit.)
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Use an initial clap (or 4 claps) to mark the sync. The software searches the lead in time before the first clear notes for sharp claps and performs a best fit alignment of all the tracks using those clap(s).
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As described above, audacity can be used to override or fix or fine tune any sync issues that the automatic system was unable to resolve properly.
The software has a built in high precision audio mixer. Gains can be specified for any individual track. For example, piano accompianment of a choir can be made louder to balance out a 50 voice choir. A specific instrument (i.e. trumpet) could be softened so it doesn't dominate a piece. If a participant just isn't working out (which might happen in a kids choir for example) you can still include their video, but mute the audio and no one will know.
Video tracks are optional and can be recorded at the same time as the audio in the same clip, or they can be recorded separately with the performer lip syncing.
By default the software will find and sync any video clips in the project folder (sync based on the audio track)and draw them out in a grid pattern. The default strategy is not exciting or creative, but it is a solid and clean approach that can be done automatically with no additional software or expertise.
These tools can handle a wide variety of video formats, frames per second, aspect ratios, etc. and still grid and draw them all out properly in sync.
- Choir practice! This may not be your final performance, but you can still have participants submit their tracks and quickly mix them together so you can provide feedback and show progress.
- Some people know their band would sound a lot better if they played all the instruments. Now's your chance!
- Just uses these tools to create time aligned versions of your tracks and import those into your favorite fancy audio/video editor tools and save a ton of time.
- What other ideas do you have?
For now, these scripts require ffmpeg, and a python distribution to already be found on your system. If you don't have python already, you may find 'anaconda' a nice option. Make sure you install python version 3 (not version 2.)
These scripts depend on a few libraries that are not normally found in a standard python distribution. These extra libraries can easily be installed with "pip". For those with opinions about how to manage python dependencies, maybe your linux distribution already has some of these libraries packaged, or maybe your python system (i.e. conda) has some of these available already. It may be worth checking both of those first and then using pip if no prepackaged libraries are found.
When I do this sort of thing, I run the script, see what package import fails, install it, repeat ..., eventually I have all the dependencies and the script works, yeah!
The following has been tested on Ubuntu 20.04.
- Open terminal and open system packages:
sudo apt install sox libsox-fmt-all ffmpeg gcc g++ make- Install Anaconda or conda package manager
- Open a terminal, create environment
vchoir, and activate it.
conda env create --file environment.yml
conda activate vchoir- Run test using demo clips
python sync-tracks.py demo_clips/ --crop noneI'm sure you have many. Please feel free to ask for help! As I write this, these software tools are very young and not tested across a wide set of performances. I am new to this technology too, and learning as I go. So let's learn together; help me make these tools work easier and better.
If your performances can bring a smile to someone's face, then it's all worth while!
https://docs.google.com/document/d/1QK-PVHsBMGDT5RCx258rMFw1Aww4yGV8YkmHjXPrrsc/edit?usp=sharing
https://docs.google.com/document/d/1mWFmZ76PZErq-XEIeCNmw1FZdtWXVHjOARTSdNITCzA/edit?usp=sharing