Another observation to add to the above. I switched on the laptop from cold. It seemed to boot up correctly and the Speakers (Built-in Audio) were showing in the "Play sound through" panel of System Settings > Sound > Input. I started to play a video through the Videos app and noticed a slight crackling, the sound playback becoming intermittent. I then switched on a pair of Bluetooth headphones and, since Bluetooth was on by default, the headphones immediately connected and started playing the sound track. I then looked at the System Settings > Sound > Input panel and found that, although the Headset was listed under "Play sound through", they were not highlighted; the Speakers remained highlighted instead even though the sound was coming through the headphones. Using the trackpad to click between the two caused the sound output to be switched between Speakers and Headset. (The sound playback has remained clear and free from crackles since then and continues to play correctly whilst I am typing this comment using Firefox web Browser.)
The mystery deepens. Perhaps someone who understands the kernel operation knows where the bug lies. I do hope so. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to alsa-driver in Ubuntu. https://bugs.launchpad.net/bugs/1402194 Title: PCI/internal sound card not detected Status in alsa-driver package in Ubuntu: Incomplete Bug description: This bug relates to the internal sound hardware in a Dell XPS 13 laptop. Since accepting an upgrade to the latest Ubuntu Extra software today, the Systems Settings > Sound > Output no longer show the internal speakers, despite numerous attempts to shut down and restart. Before accepting the upgrade, the sound played normally through the speakers. Having upgraded the system from the Ubuntu 12.10 originally installed with the laptop and finding comments relating to the software drivers for the Intel WiFi and Bluetooth chip (Intel AC 7520) and touch screen, I tried out an installation straight from a Ubuntu 14.04 bootable USB stick. The system worked well enough without these drivers so I went ahead and replaced the whole installation from the USB stick and subsequently accepted the upgrade to 14.10. I tried plugging in a headset and this produced a screen allowing me to select the type of headset (mono, with or without mic or stereo). An extra entry appeared in the System Settings > Sound > Output pane allowing me to choose between the headset or the speakers and to test the audio on each one. However, unplugging the headset seemed to produce intermittent behaviour, the system being uncertain as to whether the headset was in use. This was solved by re-booting and the system and speakers behaved as expected. Now I have the situation that the speakers are not shown in the Sound > Output pane and the Output Volume slider stays at zero and is unable to be moved with the pointer. The volume control slider in the dropdown panel from the speaker symbol in the system tray appears to respond to movement from the pointer and the Fn-F11 & F12 keys. However, with no output device shown, there is no sound output to the speakers. Several attempts to restart the system have failed to restore the speaker functionality. ProblemType: Bug DistroRelease: Ubuntu 14.10 Package: alsa-base 1.0.25+dfsg-0ubuntu4 ProcVersionSignature: Ubuntu 3.16.0-28.38-generic 3.16.7-ckt1 Uname: Linux 3.16.0-28-generic x86_64 ApportVersion: 2.14.7-0ubuntu8 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: david 2172 F.... pulseaudio CurrentDesktop: Unity Date: Sat Dec 13 13:28:32 2014 InstallationDate: Installed on 2014-12-11 (1 days ago) InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2) PackageArchitecture: all ProcEnviron: LANGUAGE=en_GB:en PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_GB.UTF-8 SHELL=/bin/bash SourcePackage: alsa-driver Symptom: audio Title: PCI/internal sound card not detected UpgradeStatus: Upgraded to utopic on 2014-12-11 (1 days ago) dmi.bios.date: 09/11/2014 dmi.bios.vendor: Dell Inc. dmi.bios.version: A05 dmi.board.name: 0D13CR dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 8 dmi.chassis.vendor: Dell Inc. dmi.chassis.version: 0.1 dmi.modalias: dmi:bvnDellInc.:bvrA05:bd09/11/2014:svnDellInc.:pnXPS139333:pvr:rvnDellInc.:rn0D13CR:rvrA00:cvnDellInc.:ct8:cvr0.1: dmi.product.name: XPS13 9333 dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1402194/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp