audio recording from usb microphone with linux ubuntu 16, ffmpeg, arecord,

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  2 
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  4 # audio recording from usb microphone
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  6 with linux ubuntu 16, ffmpeg, arecord,
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  8 alsamixer, lsusb, audacity
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 10 
 11 
 12 ref:
 13 
 14     https://trac.ffmpeg.org/wiki/Capture/ALSA
 15 
 16     http://tuxradar.com/content/how-it-works-linux-audio-explained
 17 
 18     http://trac.edgewall.org/
 19 
 20 
 21 ## ALSA, OSS
 22 
 23 On Linux, recording with a USB microphone is best done under ALSA
 24  (Advanced Linux Sound Architecture). Current Audacity provides native
 25  ALSA support. 1.2.x versions of Audacity only support the older OSS
 26  (Open Sound System), but can work with ALSA using an OSS emulation
 27  layer.
 28 
 29 
 30 ## capturing from ALSA
 31 
 32 Capturing audio with ffmpeg and ALSA is pretty much straightforward:
 33 
 34     ffmpeg -f alsa <input_options> -i <input_device> ... output.wav
 35 
 36     -f fmt (input/output)
 37 
 38         Force input or output file format. The format is normally auto
 39         detected for input files and guessed from the file extension
 40         for output files, so this option is not needed in most cases.
 41 
 42     -i url (input), input file url
 43 
 44 
 45 ## Selecting the input card
 46 
 47     input_device tells ffmpeg which audio capturing card or device you
 48     would like to use. To get the list of all installed cards on your
 49     machine, you can type arecord -l or arecord -L (longer output).
 50 
 51 To list recording cards or devices:
 52 
 53     $ arecord -l
 54 
 55         **** List of CAPTURE Hardware Devices ****
 56         card 0: ICH5 [Intel ICH5], device 0: Intel ICH [Intel ICH5]
 57         Subdevices: 1/1
 58         Subdevice #0: subdevice #0
 59         card 0: ICH5 [Intel ICH5], device 1: Intel ICH - MIC ADC [Intel
 60         ICH5 - MIC ADC]
 61         Subdevices: 1/1
 62         Subdevice #0: subdevice #0
 63 
 64 We can see there are 2 audio cards installed that
 65 provide capturing capabilities, namely "card 0"
 66 (Intel ICH5) and "card 1" (Microphone on the USB
 67 web cam). The easiest thing to do is to reference
 68 each of them directly using
 69 
 70     -f alsa -i hw:0
 71 
 72     #@or
 73 
 74     -f alsa -i hw:1:
 75 
 76 
 77     ffmpeg -f alsa -i hw:1 -t 30 out.wav
 78 
 79     That will give us a 30 seconds WAV audio output,
 80     recorded from our USB camera's default recording
 81     device (microphone). The default recording device
 82     can be selected using the alsamixer tool (see
 83     below) or specifying the device using an
 84     additional parameter Y in hw:<X>,<Y>, where
 85     <X>=card, <Y>=device. For example, to select "MIC2
 86     ADC" from Intel card (look above at the list), we
 87     would use:
 88 
 89     ffmpeg -f alsa -i hw:0,2 -t 30 out.wav
 90 
 91 The best way is to select your card and default
 92 recording device with the alsamixer tool, because
 93 some audio cards have a complicated way of
 94 selecting the default input through the ffmpeg
 95 command line.
 96 
 97 
 98 ## Input options
 99 
100 The only useful audio input options for ALSA input are -ar (audio sample rate)
101 and -ac (audio channels).
102 
103 Specifying audio sampling rate/frequency will force the audio card to record
104 the audio at that specified rate. Usually the default value is "44100" (Hz).
105 Specifying audio channels will force the audio card to record the audio as
106 mono, stereo or even 2.1/5.1 (if supported by your audio card). Usually the
107 default value is "1" (mono) for Mic input and "2" (stereo) for Line-In input.
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109 
110 Another option for ffmpeg:
111 
112     -thread_queue_size 512
113 
114 
115 ## Example
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117 Record audio from the microphone
118 
119 
120     ffmpeg -f alsa -ac 1 -ar 44100 -i hw:0 -t 30 out.wav
121 
122     ffmpeg -thread_queuq_size 512 \
123         -f alsa \
124         -ac 1 \
125         -ar 44100 \
126         -i hw:0 \
127         -t 30 \
128         youFileName.wav
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130 
131 
132 
133 ## end of part 1
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135 <!-- vim: set tw=70 ft=markdown nowrap fdm=marker ignorecase: -->