Replies to This Discussion

Permalink Reply by Spencer "Thunderball" Thayer! on June 25, 2011 at 3:44am

I've used this within my own home. I thought it was sufficient but noticed a high enough latency to detect if you were walking from one room to another REALLY fast. I ended up just running a 50 foot cable from one room to another.

 

Anyway I think the primary problem would be maintaining an established connection while on the ride. Many of the places we go my 4G coverage will drop to 3G and that'll cause a hicup in the throughput. Worse is when it drops completely which is common. I don't think the wimax or cellphone carries are ready for prime time yet.

 

BUT with that said. I would still totally love to try it. : )

Permalink Reply by Matt on June 25, 2011 at 3:57am

I know this is something you have been trying to do for years. Exciting! Just downloaded the speakers app to my iPhone. Will be riding with Boston Critical Mass in July but put me on Team Airfoil in August!

Permalink Reply by Todd Allen on June 25, 2011 at 3:51pm

I mostly agree with Spencer.  Because this app transmits the audio stream if you don't have a solid connection it will pre buffer.  If it pre buffers you will have latency.  When the buffer is insufficient you will have audio dropouts, similar to watching internet videos over a bad connection.

 

A much better solution would be to write a custom app that merely sends syncing signals and can tweak playback rates when playback has drifted from a received sync signal.  Even better would be if all receivers would echo the sync with an increasing echo tag.  Each receiver would only utilize and re-echo the lowest echo they get.  This would allow truly synced playback over a very large mass.    Everyone would need to preload the entire playlist on their device, but then one could go completely out of range of everyone else for  a long while and seamlessly continue playing and resyncing when getting back in range.

Permalink Reply by Spencer "Thunderball" Thayer! on June 26, 2011 at 4:21am

I was assuming you were going to try something else. This could certainly work. If we are to rely on something like that why not use remote mics or a high power FM transmitter? Some of these can got for blocks without a problem and everyone can get a cheap FM radio. The same problem that you would have with 802.11 downtown would be the same problem you would have with an FM transmitter only the wave form of the transmitter is capable of traveling longer distances and is able to penetrate more materials.

 

http://www.amazon.com/0-5-Fail-Safe-Long-Range-Transmitter/dp/B003F...

http://www.amazon.com/Fail-Safe-Professional-Transmitter-CZH-15A-An...

Permalink Reply by Spencer "Thunderball" Thayer! on June 26, 2011 at 4:28am

The only issue would be that the source audio would of course be ahead of the transmitter. Simple solution... Only play the source through the FM transmitter and use a receiver through ones own sound system. If this is something people would actually want to use I would consider getting one of these. I think the thing about building your own sound bike is that you want to play yer own thing. Be your own personal DJ and I am not sure if the level of participation it would be worth the cost.

Permalink Reply by Todd Allen on June 26, 2011 at 6:00am

300 feet is not very far.  And the signal gets weak and the bandwidth drops off badly.  Don't think about the best case of a couple bikes fairly close together with a clean line of sight.  Think the worst case of travelling around a corner downtown with a massive stone and steel building in between the transmitter and receiver.  And possibly dozens of other nearby devices operating on the same channel.  And a large number of bodies, bicycles and other random obstructions all constantly passing in between and interfering with the signal.

 

Do you know the packet protocol your device uses? ie UDP or TCP?  If it is TCP it will be more robust with a single transmitter and receiver but is unlikely to scale well with multiple receivers.  If it is UDP it will likely scale better, but likely not handle dropped packets as well.

Permalink Reply by gadgetguy on June 27, 2011 at 11:40am

This definately sounds like a cool idea.

With regards to the range problem, is there some way of setting up repeaters?

 

If this gets up and going I hope it is called "Critical Bass".

Permalink Reply by gadgetguy on June 28, 2011 at 6:11am

It seems that a clever program would buffer the stream and utilize some type of time synching method (off a GPS signal perhaps?).  A very clever program would actually use the relative locations of the recievers to adjust for phase shift.

Someday someone will figure this out. 

A less elegant solution would be to have the music preloaded on all the sound sources, then simply coordinate from a common time signal (again perhaps GPS) so there is no transmission during the event at all.

Permalink Reply by gadgetguy on June 28, 2011 at 6:48am

With regards to the dynamic system, the software would have to constantly readjust for the changing locations of the players.   This would be possible (although with alot of work) and yes, any lag would be problematic (but thats why I mentioned buffering the stream).   You are never going to have optimum sound quality, but im sure something listenable is possible.

 

With regards to the prerecorded option, you need all the players synched (constantly), so if one has problems it simply drops out until it can get to the same spot everyone else is at.

 

I dont mean to imply any of this is easy.  It is a very worthwhile project.