====== Sending Microphone Input to another device over TCP ======

===== How it Works =====
  * Essentially we are using **NETCAT** to pipe audio from a mic input on one computer to the audio output of another computer.
  * It appears that **ssh** adds a lot of latency around 1-2 secs which is not acceptable more most instances
  * Netcat on the receiver need to starts before the transmitter starts to send otherwise the transmitter script will exit with a connection refused. 

===== Requirements =====
  * **Alsa** needs to be working on both computers and alsa-utils should be installed to save mixer settings
  * **aplay/arecord** also need to be installed along with **netcat**.  In most distributions they are installed as base packages
  * Obviously some sort of tcp/ip must be running to for the netcat communication to work. 

===== Wifi Setup =====

<file bash /etc/network/interfaces>
...
auto wlan0
iface wlan0 inet dhcp
        wpa-ssid ssid
        wpa-psk ####

...
</file>

===== Audio setup =====

  * By default the usb audio adapter is detected as card 1 not card 0(default).  I tried disable the bcm sound module but for some reason that disables the mixer of the usb audio adapter.
  * I was able to set the default card using asound.conf

<file bash /etc/asound.conf>
pcm.!default {
    type hw
    card 1
}

ctl.!default {
    type hw
    card 1
}
</file>

====== Receiver ======
<file bash wifi_audio_recv.sh>
#!/bin/sh

PORT="8080"
RATE="2"
BUFFER="10"
FORMAT="cd"

while [ true ]
do
        netcat -l -p ${PORT} | aplay -B ${BUFFER} -r ${RATE} -f ${FORMAT}
done
</file>

====== Transmitter ======
  * **RECV_ADDR** will need to changed to something valid like a ip address or a hostname/fqdn.
<file bash wifi_audo_send.sh>
#!/bin/sh

PORT="8080"
RATE="2"
BUFFER="10"
FORMAT="cd"

RECV_ADDR="<IP>"
RECV_PORT="8080"

arecord -B ${BUFFER} -r ${RATE} -f ${FORMAT} | netcat ${RECV_ADDR} ${RECV_PORT}
</file>

====== Audio Passtrough ======
  * Check mixer controls for input ampifcation if clipping occurs
<file>
arecord  -f S16_LE -c2 -r48000 -f dat | aplay -f S16_LE -c2 -r48000 -f dat
</file>


====== Price List ======

[[https://docs.google.com/spreadsheets/d/1jROjZBKDP32I1MQKS9gV2c9oLo5q8K8QiZUgWr6fepo/edit#gid=333349986|Price List]]

====== Parts List ======
  * Arm Computer
  * Wifi Adapter
  * Audio Adapter
  * Power Supply
  * Flash Card (Storage)

====== Raspberry Pi Issues ======
  * I get this error whenever I try to change either the buffer size, buffer time, or interrupt period on both the R Pi 1 and R Pi 2<file>aplay: set_params:1305: Can't use period equal to buffer size (256 == 256)</file> 
  * I picked up a C-Media CM108 Chipset usb audio adapter and it fixed the problem.  I able to adjust the sample and buffer size [[http://www.amazon.com/External-Adapter-Windows-Drivers-Needed/dp/B00V9E9YRG|Link]]
====== Other Notes ======
  * The "Chip" microcomputer looks really promising it includes storage, wifi, and audio all on board and is selling for $9.  Their website says they will be shipping in June 2016 [[http://getchip.com/]]