# BPI-R1 MIC **thank chaos.dennis do this test:** i write about this, because i found very few sources and had to tumble a lot around to get it working. This is a quick walk through to give you a hint where to start. I asume for simplicity that you stay always in /root directory as root user. If something fails, look if the files are written and paths are right. It is adressed for more advanced users who know what they are basically doing. This is done with bananian 15.08 on Kernel 3.4. Other kernels < 4.4 do not work. It is a headless server with no HDMI pluged in. **A. Basic Setup** * Install alsa (renove pulseaudio if present): `# apt-get install alsa-base alsa-utils` * Configure asound.conf `# nano /etc/asound.conf` * Should look like: ``` pcm.!default { type hw card 0 # for headphone, turn 1 to 0 device 0 } ctl.!default { type hw card 0 # for headphone, turn 1 to 0 } ``` * Shutdown, make a cold boot * Call the alsamixer `# alsamixer` Press F5. Your channels should be setup like the attached file at the bottom of this post, or compare it to amixer output: ``` # amixer Simple mixer control 'Master',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 63 Mono: Playback 45 [71%] Simple mixer control 'Master Capture Mute',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [off] Simple mixer control 'LineL',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'LineR',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Linein Pre-AMP',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 7 [100%] Simple mixer control 'Mic Input Mux',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 15 Mono: 15 [100%] Simple mixer control 'Mic Power',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Mic1 Boost',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Mic1 gain',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 3 Mono: 3 [100%] Simple mixer control 'Mic2 Boost',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Mic2 gain',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 0 [0%] Simple mixer control 'MicL',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 3 Mono: 1 [33%] Simple mixer control 'MicR',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 3 Mono: 3 [100%] Simple mixer control 'Playback',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Capture',0 Capabilities: cvolume cvolume-joined Capture channels: Mono Limits: Capture 0 - 7 Mono: Capture 7 [100%] Simple mixer control 'ADC Input Mux',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 7 [100%] Simple mixer control 'Fm output',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 7 [100%] Simple mixer control 'FmL',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'FmR',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'LINEIN APM',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 7 [100%] Simple mixer control 'Ldac Left Mixer',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Ldac Right Mixer',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Left Capture Mute',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'MIC output volume',0 Capabilities: volume volume-joined Playback channels: Mono Capture channels: Mono Limits: 0 - 7 Mono: 7 [100%] Simple mixer control 'Rdac Right Mixer',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] Simple mixer control 'Right Capture Mute',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] ``` This step is critical. One false muted channel and you are out of the game. * Test recording. `# arecord -L` Should show a device. `# arecord -f S16_LE -r 44100 -t wav test.wav` Should make kind of Sound. Stop it with ctr-c and check the file. **B. SoX Recording / Streaming** * Install SoX `# apt-get install sox libsox-fmt-all` Sox gives you tools like: sox, rec and play. I would suggest you install it on the client pc too. * Record striaght to mp3 ``` # rec -c 2 -C 64 test.mp3 ``` -c 2 two channels -C 64 tell the encoder to produce a 64kbit/s mp3 Stop it with ctr-c, check the output. * Listen to it live over LAN Banana: `# rec -c 2 -C 64 -t mp3 - | netcat -l -p 9000` -t mp3 - produce mp3 stream to stdout Client: `# netcat 9000 | vlc` Works? Great! Live listening is important to play around and test the mic. * Listen and record at same time `# rec -c 2 -C 64 -t mp3 - | tee test.mp3 | netcat -l -p 9000` * Poor man's streaming server ``` # apt-get install openbsd-inetd tcpd ``` Edit config file: ``` # nano /etc/inetd.conf ``` Insert this at the end: ``` 9000 stream tcp nowait nobody /usr/bin/tail tail -f /test.mp3 ``` Restart service ``` # service openbsd-inetd restart ``` Start recording on banana: ``` # rec -c 2 -C 64 /test.mp3 ``` Connect via client: ``` # netcat 9000 | vlc - ``` **C. Advanced Recording** * Devide recording and postprocessing in two parts ``` # rec -t raw - remix - | sox -t raw -r 48000 -c 1 -b 16 -e signed-integer - -t mp3 -c 1 -C 32 test.mp3 ``` **Recording:** **-t raw** - forward raw input to pipe **remix** - Mix the two channels to one **Encoding:** **-t raw -r 48000 -c 1 -b 16 -e signed-integer** - tell sox what kind of strean comes from stdin **-t mp3 -c 1 -C 32 test.mp3** and what goes out Note that it is switched to mono from here with -c 1 and the mp3 bitrate is cut in half. Live listening to the strean does not work anymore, i asume it is because of the non regulare output from pipeing and processing in a second step. * Reduce noise The mic input is pretty bad, lot of white noise. Sox can deal with it. Make a sample "silent" file: ``` # rec -t raw test.raw remix - trim 0 10 ``` **trim 0 10** record 10 seconds Test it at client pc: ``` # play -r 48000 -c 1 -b 16 -e signed-integer test.raw ``` Create profile file: ``` # sox -r 48000 -c 1 -b 16 -e signed-integer test.raw -n trim 0 2 noiseprof raw-profile ``` Record with noise canceld ``` # rec -t raw - remix - noisered raw-profile 0.2 | sox -t raw -r 48000 -c 1 -b 16 -e signed-integer - -t mp3 -c 1 -C 32 test.mp3 ``` Play with the factor of 0.2 to regulate the intensity of cancellation. **D. Record 24/7** My goal of this.... Create a script: ``` # nano /root/record.sh ``` Insert the following: ``` #!/bin/bash # send sigterm and wait for exit of the process function stop() { kill $@; while kill -0 $@; do sleep 1; done; } function log() { echo $(date +%T) $@; } log "Stopping previus recording" stop `pidof rec` &> /dev/null DATE=`date "+%Y.%m.%d"` log "Recording $DATE.mp3" rec -q -t raw - remix - noisered /root/raw-profile 0.2 | \ sox -v 2.0 -t raw -r 48000 -c 1 -b 16 -e signed-integer - \ -t mp3 -r 22050 -c 1 -C -9.2 /root/$DATE.mp3 log "Done $DATE.mp3" ``` **Recording:** **-q** less output **Encoding:** **-v 2.0** Make the input stream louder **-r 22050** encode to a lower sample rate **-C -9.2** Create a low quality VBR mp3 Fileszie \~100mb per day. If you want smaller files, a 8000 sanple rate gives you a gsm grade quality. A very good article to sample rate: Make it executable ``` # chmod +x record.sh ``` Edit crontab: ``` # env EDITOR=nano crontab -e ``` Insert at the end the following: ``` PATH=/usr/local/bin:/usr/local/sbin:/sbin:/usr/sbin:/bin:/usr/bin 0 0 * * * /root/record.sh >> /root/re cord-mic.log ``` A new recording should start every day at midnight. ![](https://4049603582-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M2HWtRPFCC-Z_DiL7ST%2F-M2HWw1TL1Tj7ZkprRnb%2F-M2HXPAxj9fuIVgBpO2C%2Fmic.png?generation=1584080215469116\&alt=media)