Skywave Linux

Skywave Linux is a specialized version of Ubuntu Linux with preconfigured amateur radio related software and utilities.

In 2016 Skywave Linux 2.0 was released. It should use Ubuntu 16.04 LTS base system, kernel 4.4.0-41-lowlatency.
Upon installation a uname -r reveals: 4.4.0-45-lowlatency
At this time the most current long term release of Ubuntu Linux is also 16:04.

working though post-installation problems

unknown monitor

I found that my monitor could not be properly detected when I used an analog VGA connector. Connecting via HDMI resoloved the problem.

no audio when using HDMI only

The PulseAudio mixer shows audio on the Output Devices "Built In Audio" but you hear no sound from the monitor / tv speakers.

1. Open Pulseaudio
2. Click the "configuration" tab and set profile to "Digital Stereo (HDMI) Output"
3. Click the "playback" tab and set the specific application to "Built-in Audio Digital Stereo (HDMI)"

The system still defaults to the analog audio output, however, you are specifically setting each individual application audio output directing it to HDMI. This is not as elegant as a solution that defaults to HDMI output.

no sound / pulseaudio freezes machine

You have a choice to make here if you are having audio problems. You can try to get things working with pulseaudio or you can dump it for the more basic alsa sound system. PulseAudio is problematic.

WARNING: On new releases of Ubuntu the developers have deeply embedded pulseaudio dependencies into the sound system. On the Ubuntu web site they strongly discourage removal of Pulseaudio. Proceed to remove it if you are very familiar with ALSA and the specific audio card driver.

Find out what you have for a sound card and audio sources.

aplay -l

This will list the sound card id and the device number for the output type. It might look something like this:

**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 1: ALC892 Digital [ALC892 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

In this example we can see that the sound card id is 0 and that there are two HDMI output devices. I connected my HDMI cable to the first one, HDMI 0, which we can see is "device 3." So now that we know that we can use aplay to test and listen for sound

aplay -D plughw:0,3 /usr/share/sounds/alsa/Front_Center.wav

That particular audio file comes with your Skywave Linux installation. Notice I purposely specified the card id and device number.

1). Option I - attempt to resolve "no sound" issue with PulseAudio. If this fails then it is recommended to go to Option II.

2). Option II - Remove PulseAudio & use ALSA

The ALSA sound server does not have all of the features of PulseAudio, however, it seems to be far more stable.

Skywave uses PulseAudio as the default sound server. But since PulseAudio cannot directly communicate with the audio hardware, it still needs tools like ALSA to function. We can remove pulseaudio and configure the system to use only ALSA. First remove pulseaudio.

sudo apt-get remove pulseaudio

You will no longer have a volume control mixer applet. Now you can install one for ALSA.

sudo apt-get install gnome-alsamixer
gnome-alsamixer

In the alsa control applet I had to check the box IEC958 which then allowed me to hear audio via the HDMI cable.