Slashdot Mirror
RockBox + Refurbished MP3 Players = Crowdsourced Audio Capture
An anonymous reader writes "Looking for an inexpensive means to capture audio from a dynamically moving crowd, I sampled many MP3 players' recording capabilities. Ultimately the best bang-for-the-buck was refurbished SanDisk Sansa Clip+ devices ($26/ea) loaded with (open source) RockBox firmware. The most massively multi-track event was a thorium conference in Chicago where many attendees wore a Clip+. Volunteers worked the room with cameras, and audio capture was decoupled from video capture. It looked like this. Despite having (higher quality) ZOOM H1n and wireless mics, I've continued to use the RockBox-ified Clip+ devices ... even if the H1n is running, the Clip+ serves as backup. There's no worry about interference or staying within wireless mic range. The devices have 4GB capacity, and RockBox allows WAV capture. They'll run at least 5 hours before the battery is depleted (with lots of storage left over). I would suggest sticking with 44kHz (mono) capture, as 48kHz is unreliable. To get an idea of their sound quality, here is a 10-person dinner conversation (about thorium molten salt nuclear reactors) in a very busy restaurant. I don't know how else I could have isolated everyone's dialog for so little money. (And I would NOT recommend Clip+ with factory firmware... they only support 22kHz and levels are too high for clipping on people's collars.)" This video incorporating much of that captured audio is worth watching for its content as well as the interesting repurposing.
Sorry, I have no idea what TFA is about. Please help.
...omphaloskepsis often...
Maybe I'm misunderstanding the process here, but this seems like it would create a HUGE amount of editing work. Are you manually switching which recorder's audio is used as different people speak? In other words, editing the video using as many simultaneous audio tracks as there are recorders, syncing them, and using the best one at any given instant during the video? That seems like it would add huge amounts of editing time.
I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
tl:dr Recipe for recording the audio of multiple individuals in a large crowd.
Ingredients:
Sandisk Sansa Clip+ MP3 Player - http://www.sandisk.co.uk/products/sansa-music-and-video-players/sandisk-sansa-clipplus-mp3-player
Rockbox - http://www.rockbox.org/
Instructions:
Install Rockbox (open source firmware for MP3 players) on the Sansa Clip+. Configure to record on the Sansa Clip+ microphone in .wav format. Give a Sansa Clip+ to every person you want to record the audio for. Have every person start recording at roughly the same time, leave for 5 hours.
Gather all Sansa Clip+s at the end of the session, and extract the .wav file. 10-participants = 10-track equivalent audio recording of the session.
Mix and fade between the tracks to isolate the audio of single conversations between participants.
He basically has created a relatively inexpensive and reliable way to get this audio. Much like using multiple Go Pro cameras to record action of sports events beats out using professional equipment (and in some ways has become professional equipment). He's arguing that the Sansa Clip+ together with the Rockbox open source firmware, is a better solution than using professional radio mic's and then having recording equipment receive those signals and store them on disk for editing later.
I've no idea how "crowdsourced" fits into this though, nor how this is anything more than an advert even though the solution is a little interesting. It's useful enough and potentially cheap that you might imagine giving everyone at a Ted one of these as the conversations caught off-record might be even more valuable than the sessions.
Computers are good for that sort of stuff, and something very similar has been done using them for around forty years. Seismic surveys consist of a large number of devices that strongly resemble a moving coil microphone, and recordings from those devices are stacked (added together) so that random or location specific noise is reduced and the common signal is amplified. There's a bit more than that in seismic surveys due to wide spacing between receivers, but that's not relevant with microphones just about on top of each other in the same room. Getting the start time the same on all the audio samples and adding them together will get increase the signal (conversation at the table) over the noise (conversations from other tables which will be much louder at some microphones and less audible from others).
The most massively multi-track event was a thorium conference
About a specific isotope, or was it more generic?
Sent as ripples into the electromagnetic field. No single photon has been harmed in the process.
Will this also work for the newer Clip Zip? It's about the same price but with even more features.
Sandisk Sansa Clip Zip
http://www.amazon.com/SanDisk-Sansa-Clip-Player-SDMX22-004G-A57K/dp/B005FVNGRS/
The Rockbox support page for the Clip Zip makes it sound like the firmware is pretty solid.
http://www.rockbox.org/wiki/SansaClip#Sansa_Clip_Zip_port_status
Interesting idea, but it sounds like a pain in the ass to deal with in post production. Each recorder is running off it's own crystal for timing, with each crystal being ever so slightly different. This is why the professional approach is to route a mic signals to one recorder, or if you need more channel capacity to sync recorders to the same master clock.
It's a neat hack, with some usefulness if you cherry pick recordings and edit the best parts together without mixing/overlapping sources together.
My ears got plugged up while swimming and I could barely hear the next day. Rockbox's recorder function outputs the microphone to headphones even when it is not recording. That $30 Clip+ worked reasonably well as a makeshift hearing aid, as long as I was facing the person I was trying to hear.
This is precisely the technique I developed for recording audio in the award winning film Ten Canoes (http://www.imdb.com/title/tt0466399/), filmed in 2005. The challenge there was 10 naked actors, in a crocodile/leech/mosquito infested swamp, speaking Yolngu dialect language, so conventional mic techniques were not feasible. I use MSI Megastick-256 at 16kS/s, disposable AAA batteries and external 1/4" electret mics woven into the actors' hair (or in their string bags for the bald characters). There were three big challenges: 1. Reliable transfer, 2. Reliable archiving (the memory devices have no real time clock, so we needed a technique for keeping track of actors and dates) and 3. Jitter. The ADPCM voice codec would occasionally skip multi-20ms blocks, requiring tedious editing. The big positives were: we had no near-far issues with dialogue at a distance; we could edit out extraneous dialogue (eg actors in the background discussing the film in pidgin) and we had hours of folie for atmosphere.
Audio sync in post will be a NIGHTMARE. Been there done that.
and isolating people at a dinner party is not hard, 11 people? 11 wireless microphones into a field mixer and then into the camera. OR do it old Skool. Camera guy + audio guy with a boom and a shotgun microphone on it, Two would be better (two audio guys on mic booms) A pair of ME55's in a dead cat are magical.
Do not look at laser with remaining good eye.
Nobody uses GoPro cameras. They use the Go Pro Hero HD2 pro version ofthe camera. Huge difference between the low end crappy GoPro and the Professional model in video quality.
Although audio still sucks horribly on all Go Pro cameras.
Do not look at laser with remaining good eye.
It's been a while since I checked the list of hardware at Rockbox.org, but IIRC, the newer Sansas are locked down and can't run Rockbox. Plus, they don't seen to age well; after the second Clip that just stopped responding, I switched to an iRiver - though I've never done any recording.
This reminds me of the movie "The Conversation" where Gene Hackman's character is recording a private conversation between two people in a public square. He uses small pieces gathered from multiple sources to try to piece together the whole discussion.
In Illinois, the law, under strict interpretation, requires the consent of all parties before you can eletronically record or intercept any conversation, it could be pursued as a felony offense otherwise... although current opinion is this only applies to recording conversations that you could not otherwise naturally hear with your ears.
Anyhow, check and know the recording laws in your area beforehand.
audio's great, just not when trapped in that little box. try running some cable to a mic.
And your so-called "pro" version is still thunderously cheaper than anything else.
I don't think the article was meant to mean the approach to audio/video capture they took was "better" than using professional body-pack mics and professional recording gear. I think the point was how such could be accomplished when funds aren't available for the professional gear...
After having watched a bit of the video they linked, I'd say it did rather well.
bork bork bork!
This might make smartphone videos worth a toss. The audio's pretty terrible on those. Demux the video, mux it with the audio, and you'd be good. Not perfect, but good enough for YouTube.
BTW, if anyone wants to experiment with this, Newegg's selling some refurbed Clip+ players for $26 here.
Being a smartass is a much better thing than being the alternative.
I've no idea how "crowdsourced" fits into this though, nor how this is anything more than an advert even though the solution is a little interesting.
RockBox is an open source firmware replacement for the Sansas. Also, he's (sort of) getting his audio from crowd members, instead of a room mic.
The Daddy casts sleep on the Baby. The Baby resists!
Wavpack (.wv) is fully supported on the Fuze (with Rockbox obviously), I figure I would also be useful on the Clip. It's a royalty-free lossless compression format, and beats the shit out of .WAV
The real tl:dr, in line with the anniversary mo(o)d... ;-)
;-)) in just a few years (actually, everyone minus the millions who'll get jailed for accidently looking at or listening to anything copyrighted for more than 30 milliseconds while on).
Great idea BTW. Now just think of the kind of footage (including audio) we'll get when everyone is wearing/wielding their Google Glasses (or Sights for that matter
I see a lot of clip+ offered at $38+s/h, but nothing near 26, and I couldn't find refurb site-link please!