Specifications

D. Recording Video and Sound with Bttv
In addition to the applications referenced in Section 5, recording can be managed from the command line. The
issues discussed here with regard to sound capture deal only with the default kernel−2.6 and higher sound
system: the Advanced Linux Sound Architecture.
The easy part is grabbing the video, for which we will use streamer, available with the Xawtv suite. Sound is
another matter, however. You will need to access your mixer settings using amixer, the ALSA command−line
mixer that should be available in the ALSA−tools package available from your Linux distributor. See man
amixer to follow the command line options.
Your recording can be managed either using your primary soundcard if you have your Bt8x8 audio output
connected to a mixer conduit that allows for capture (e.g. the 4−pin analog CDROM input slot), or the Bt8x8
card itself using the btaudio module. The following steps utilize the latter. First, identify the individual cards
on your system (requires /proc filesystem):
$ cat /proc/asound/pcm
00−00: Intel ICH : NVidia CK8S : playback 1 : capture 1
00−01: Intel ICH − MIC ADC : NVidia CK8S − MIC ADC : capture 1
00−02: Intel ICH − IEC958 : NVidia CK8S − IEC958 : playback 1
01−00: Bt87x Digital : Bt87x Digital : capture 1
01−01: Bt87x Analog : Bt87x Analog : capture 1
The first column indicates the system numbering of your available sound devices, i.e., card 0 is the soundcard
and card 01, or 1, is the Bt8x8.
Next, identify the mixer controls for the Bt8x8 card.
$ amixer −c 1 controls
numid=3,iface=MIXER,name='Capture Source'
numid=2,iface=MIXER,name='Capture Boost'
numid=1,iface=MIXER,name='Capture Volume'
Then identify the item settings of each:
$ amixer −c 1 cget name='Capture Source'
numid=3,iface=MIXER,name='Capture Source'
; type=ENUMERATED,access=rw−−−,values=1,items=3
; Item #0 'TV Tuner'
; Item #1 'FM'
; Item #2 'Mic/Line'
: values=1
$ amixer −c 1 cget name='Capture Boost'
numid=2,iface=MIXER,name='Capture Boost'
; type=BOOLEAN,access=rw−−−,values=1
values=on
$ amixer −c 1 cget name='Capture Volume'
numid=1,iface=MIXER,name='Capture Volume'
; type=INTEGER,access=rw−−−,values=1,min=0,max=15,step=0
: values=0
Use cset for the capture source:
$ amixer −c 1 cset name='Capture Source' 0
...and to set the volume:
$ amixer −c 1 cset name="Capture Volume' 15
...and you should be ready.
D. Recording Video and Sound with Bttv 39