Changes
much more details
[[Category:Ongoing_Projects]]
== Description ==
* Hardware / Software solution to enable live interpretation of talks, anywhere there's IP and power (we could use power banks as USB UPSs) ''Could be simplified as a simple IP intercom / duplex HW-SW stack''
== Goal ==
* At least two mic/headphones
* Cheap
* OSS / OSHW
== Obstacles ==
* Network , software mixing and codec latency
* Mics getting ambient noise
== Component Components ==* Raspberry pi (zero?)or other GNU/Linux embedded system with USB, ethernet and GPIO
* pots, switches and LEDs
* USB mic-headphones
* OGG Opus
* Power source
* [2 line lcd?]
== HW details ==
We need a mute momentary switch. Also a buzzer (to diagnose start-up / majors problems)
All of what follows will be implemented twice par device (or plus).
USB port for the audio devices, and a way to be sure which is which.
Two (digital?) pots (mic and headphone gains)
A enable/disable switch (with built-in led if cheap enough?)
One LED to indicate if a mic is open (if not inside switch).
We map the digipots to alsa volume controls.
== SW details ==
Then, let's assume a GNU/Linux distro
'''Setup:'''
Parameters such as audio source (upstream) IP:port, also downstream IP:port and codec parameters are stored somewhere (sd)
Also the language code of the stream (can we mux this somehow, or is it upstream's responsiblity)
Optionally drive a 2line led display and have enough buttons to set ip:ports and number of devices?
'''On boot:'''
Enumerate USB devices. If one is absent, keep beeping its led. If both are absent, buzz till reset.
If an upstream is set, attempt connection. If no connection, buzz / blink in another pattern.
Software mix both sources and feed the output into an OGG Opus encoder. Stream this (UDP broadcast? or set ip:port)
(Optionally mix upstream with lower level)
'''While true:'''
while mute button is pressed:
Cut USB inputs. Don't change upstream level.
If no input is enabled, Upstream level = 1;
If at least one input is enabled, Upstream < 1;
On upstream failure: attempt reco (maybe double beep and blink)
On downstream failure: same (maybe triple beep and blink)
== Roadmap ==
* Test streaming a mono Opus to a raspi, look at usage, figure out a couple quality / latency settings.
* Test encoding a mono Opus from a raspi, same.
* Test doing the same with software mixing enabled (broadcasting a mix of the input stream and some local audio)
* Test doing the same using an USB audio device as playback and capture at the same time.
* Double it.
* Figure out how to GPIO efficiently at the same time (implement buzzer and visual alerts)
* Figure out how to control audio volumes via GPIO
* Test the darn thing in a real setting
* Monitor power use, derive estimation of battery-operation capacity
== Participants ==
* [[User:Fzn]] (Leader)
