Dell XPS 15 2016 with Ubuntu 16 Sound HDMI issues

[Daniel Rodriguez]

This issue is related to sound not working properly on Ubuntu when switching between an external display using HDMI with 4K resolution and the standard laptop display.

Issue 1 - Sound only works on laptop when plugged into 4k HDMI display
Issue 2 - Sound doesn't work when plugged removed from 4k HDMI display

When you plug in a 4k Display that supports sound to the Dell XPS 15 2016 model the sound only works on the laptop. Only when you go to Sound Settings and manually select the HDMI output for sound does the sound start to work on the display itself instead of the laptop.

When you unplug the HDMI 4k display the sound doesn't work on the laptop. When you go to the Sound Settings dialog it only shows one output that is selected - if you select the same output thats already selected the sound starts to work again on the laptop.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Hui Wang (hui.wang)]

I don't think the issue 1 is a problem, since the pulseaudio's design is just like that. In the pulseaudio, the HDMI output does not have higher priority than internal speaker. If users want the sound output via HDMI, users need to select it manually.

For issue 2, it is really a problem, and I can reproduce this problem on my own laptop, so it is a common problem instead of specific to Dell xps 15 and 4K monitor.

I am debugging the pulseaudio's code and u-c-c's code, try to fix this problem from either PA or u-c-c.

[Jared Dominguez (jared-dominguez)]

It sounds to me like issue 1 should be opened as a separate bug report as a feature request. I think it makes sense to at least prompt the user whether they want to switch to external audio.

[Hui Wang (hui.wang)]

Yes, I agree with the comment #4.

[Hui Wang (hui.wang)]

And for issue #2, I found if we open the u-c-c when unplugging the HDMI cable, the issue #2 will not happen. But it does not make sense to keep the u-c-c opened all the time since it is not a daemon app.

So I think it is difficult to fix this problem in the u-c-c, I will focus on looking for a solution in the pulseaudio.

[Hui Wang (hui.wang)]

Sent a patch for pulseaudio to fix this problem. The track URL is here:
 https://lists.freedesktop.org/archives/pulseaudio-discuss/2017-April/028083.html

[Hui Wang (hui.wang)]

Looks like this issue is fixed by 3 pulseaudio patches. two of them already been merged to master branch, waiting for the last one to be merged.

[Hui Wang (hui.wang)]

The 3 fixing commits are (pulseaudio):

6b348961304903483aa78d4ddc1fd036ef75a7cb
1c477fcb679ac50259ef057ebe23c80c529aa612
4c6843f02067bed2a299bed1651d00832e2afea0

[Anthony Wong (anthonywong)]

From what I learnt from Hui Wang, it is not easy to backport these 3 commits to 16.04, or even it is not possible at all. These commits make a great change for pulseaudio core as well as some other modules, it will affect a lot of existing functions in the pulesaudio. The 1st commit looks like below. I will leave the decision to desktop team if we want to fix this in 16.04 or not.

hwang4@hwang4-Inspiron-7520:~/source/pulseaudio$ git show 6b348961304903483aa78d4ddc1fd036ef75a7cb |diffstat
modules/dbus/iface-core.c | 114 ++++++++++++++-------
modules/dbus/iface-sample.c | 10 +
modules/module-default-device-restore.c | 14 +-
modules/module-intended-roles.c | 37 +++---
modules/module-rescue-streams.c | 20 +--
modules/module-switch-on-connect.c | 30 +++--
pulsecore/cli-command.c | 20 +--
pulsecore/cli-text.c | 12 --
pulsecore/core.c | 170 ++++++++++++++++++++++++++++++++
pulsecore/core.h | 28 ++++-
pulsecore/namereg.c | 115 +--------------------
pulsecore/namereg.h | 6 -
pulsecore/protocol-native.c | 19 +--
pulsecore/sink.c | 7 +
pulsecore/source.c | 7 +
15 files changed, 370 insertions(+), 239 deletions(-)