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As far as I know only one video output, either the HDMI or RCA video socket, will work at a time. Now I want to know if this also applies to the audio output.
Will it be transmitted over both sockets, or does the 3.5mm audio jack socket stop working if HDMI is connected?
AFAIK only one audio output can be selected. You can, however, select one of them manually using amixer command:
sudo amixer cset numid=3 <n>
Where is 0=auto, 1=analog, 2=hdmi. By default it's set to auto which means HDMI if present, analog otherwise. Unlike changing video output, this change does not need rebooting.
You can have the video on the HDMI and the audio on the analog jack, but the HDMI will not have audio.
I don’t think this line forces to Pi to use the 3.5mm jack for audio output.
amixer cset numid=3 1
Given these two commands:
$ amixer -h
cset cID P set control contents for one control
$ amixer controls
numid=4,iface=MIXER,name=’Master Playback Switch’
numid=3,iface=MIXER,name=’Master Playback Volume’
numid=2,iface=MIXER,name=’Capture Switch’
numid=1,iface=MIXER,name=’Capture Volume’
I think the line I initially referenced sets the Master Playback Volume to nearly zero. The line does not seem to control whether the Pi outputs audio to the 3.5mm jack or the HDMI port.
Stephen C Phillips helped me sort this out:
http://blog.scphillips.com/2013/01/sound-configuration-on-raspberry-pi-with-alsa/
