This blog entry has a very neat way of grabbing screenshots from Android mobile devices. It boils down to a one liner (reproduced here just in case that blog vanishes for some reason and so it’s easy to find):
adb shell screencap -p | sed 's/\r$//' > screen.png
on Linux and
adb shell screencap -p | perl -pe 's/x0Dx0A/x0A/g' > screen.png
on the Mac.
Works perfectly. Thanks!
Finding PCM audio devices using the ALSA interface from software isn’t always completely trivial. On some builds for the BeagleBone Black, PCM audio devices appear as /dev/audio, /dev/audio1 etc. But this doesn’t seem to be generally true. Plus, this doesn’t definitively identify which device is which. A good way to find out is to open the pseudo file /proc/asound/pcm as it lists all the PCM devices in the system. To see what’s currently active, just cat the pseudo file:
UbuntuDev$ cat /proc/asound/pcm
00-00: ALC889 Analog : ALC889 Analog : playback 1 : capture 1
00-01: ALC889 Digital : ALC889 Digital : playback 1
00-02: ALC889 Analog : ALC889 Analog : capture 2
00-03: HDMI 0 : HDMI 0 : playback 1
01-00: USB Audio : USB Audio : capture 1
02-03: HDMI 0 : HDMI 0 : playback 1
02-07: HDMI 0 : HDMI 0 : playback 1
02-08: HDMI 0 : HDMI 0 : playback 1
02-09: HDMI 0 : HDMI 0 : playback 1
The first two numbers are the plughw card and device numbers. So, if you wanted to connect to the USB audio source for example, you could do:
snd_pcm_open (&m_handle, "plughw:1,0", SND_PCM_STREAM_CAPTURE, 0);
Prior to Android 4.0, how to do this was obvious. Now, however, you have to explicitly enable the developer options in a highly opaque way. The trick is to go to Settings > About phone and tap Build number seven times (some people say five, seven is from the Android documentation). Then Developer options will appear in Settings.