感谢chaos.dennis做这个测试:
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. 基本设置
Install alsa (renove pulseaudio if present):
# apt-get install alsa-base alsa-utils
Configure asound.conf
# nano /etc/asound.conf
Should look like:
Copy 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:
Copy # 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
Copy # 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 <banana ip> 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
Copy # apt-get install openbsd-inetd tcpd Edit config file:
Copy # nano /etc/inetd.conf Insert this at the end:
Copy 9000 stream tcp nowait nobody /usr/bin/tail tail -f /test.mp3 Restart service
Copy # service openbsd-inetd restart Start recording on banana:
Copy # rec -c 2 -C 64 /test.mp3 Connect via client:
Copy # netcat <banana ip> 9000 | vlc - C. Advanced Recording
Devide recording and postprocessing in two parts
Copy # 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:
Copy # rec -t raw test.raw remix - trim 0 10 trim 0 10 record 10 seconds
Test it at client pc:
Copy # play -r 48000 -c 1 -b 16 -e signed-integer test.raw Create profile file:
Copy # sox -r 48000 -c 1 -b 16 -e signed-integer test.raw -n trim 0 2 noiseprof raw-profile Record with noise canceld
Copy # 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:
Copy # nano /root/record.sh Insert the following:
Copy #!/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: http://wiki.audacityteam.org/wiki/Sample_Rates
编译此可执行文件
Copy # chmod +x record.sh 编辑 crontab:
Copy # env EDITOR=nano crontab -e Insert at the end the following:
Copy PATH=/usr/local/bin:/usr/local/sbin:/sbin:/usr/sbin:/bin:/usr/bin
0 0 * * * /root/record.sh >> /root/record-mic.log A new recording should start every day at midnight.
