Debian 9.0.0 installed fine on the M.2 SSD of my shiny new Udoo X86, and the video performance in firefox 52.2.0 leaves my old host for dead - but there's no audio on the HDMI, either with HDMI cable or HDMI to VGA adaptor + stereo audio cable. (Monitor switched to HDMI vs VGA, to suit, as confirmed by video working fine.) Clicking on "Sound & Video" -> "PulseAudio Volume Control" menu item, and setting "Firefox AudioStream" to 100% (0dB) still delivers only utter silence. And yet the VU-meter bar under that control is flapping about vigorously, so there's audio coming from firefox - it's just stuck in there. The "Output Devices" tab provides two options at "Port": Speakers Headphones (unplugged) but just confirms that the audio component of HDMI is implicit, hopefully. The monitor's volume control is set to 60%, as 100% of even 2.5 W/channel would be a bit much, once we clear the dead rat in the audio plumbing. But where can it be? P.S. An aside: Don't try to install from a debian "Live" .iso - that locks up in an endless loop, insisting on finding a CDROM.
Thank you, Maurice - that's a clue. Another half day of researching and debugging shows that it's not just firefox - feeding a .wav file to aplay elicits a "playing" message, but no sound. The Udoo hardware is recognised: $ aplay -L # shows: default Playback/recording through the Pulseaudio sound server ... hdmi:Card=PCH,DEV=0 HDA Intel PCH, HDMI 0 HDMI Audio Output hdmi:Card=PCH,DEV=1 HDA Intel PCH, HDMI 1 HDMI Audio Ouput hdmi:Card=PCH,DEV=2 HDA Intel PCH, HDMI 2 HDMI Audio Output We just need to tell the debian audio suite that it's there. This page: https://itsfoss.com/how-to-fix-no-sound-through-hdmi-in-external-monitor-in-ubuntu/ says that changing the default output can fix the problem. But on the LXDE desktop there is no "system settings" menu item, and "Sound & Video" offers no way to change the default. It also doesn't show HDMI as an available output, even when playing a youtube video. It is Soooooo frustrating to have waited 7 months for my little Udoo, so I can stream video, but now there's no sound. I'll dig some more, and try again on the debian list, but there's not a bite there.
Ubuntu preferred to use the headphone, and the GUI allowed me to select the HDMI device. All was fine after that. I done have Debian to look and screen shot, but I wonder if "alsamixer" can help you? https://askubuntu.com/questions/14077/how-can-i-change-the-default-audio-device-from-command-line Robert
Thank you, Robert, it might well do. However, I have now stumbled over a deeply hidden but simple fix. The "Sound & Video" -> "PulseAudio Volume Control" menu item has only 3 tabs, and the "Output Ports" tab offered no management/configuration possibilities. But there are two tiny dark triangles, and the RH one leads to hidden tabs; "Input Devices", and on clicking again, "Configuration". There, in a "Profile" selection box, it is possible to select "Digital Stereo (HDMI) Output". Once selected, it even seems to be the power-on default. (Much to my surprise, given the user-hostile perversity of the devious GUI design.) I'll see if I can find a way to affix [Solved] to the title of this thread. Even at 100% volume on the monitor, and 100% in "PulseAudio Volume Control", the sound is not loud. I'll have to see if I can raise the output level from the latter somehow.
