I cannot seem to get my intended display setting to stick (= clone internal display to the external display).

I use a netbook (Acer Aspire A0722) among other things as my music source, playing "bit perfect" audio from local content or streamed radio over HDMI to an AV amplifier. Doing this under Linux requires a bit of contorsionism as the AV amp has no screen contrary to what the desktop layer expects. I thus have to add a (1366x768@60Hz) screen resolution to the AV amp using xrandr, and, in the Display systemsettings pages, set the external "display" to that resolution. To prevent visual glitches, I also set the external display to be a clone of the internal display (not using the mirroring checkbox, which doesn't give the intended result).

Or so I did under KDE 4.11.3 (running on Linux Mint Debian). And that worked fine; after saving the configuration as the default I could connect/deconnect the HDMI cable, switch the amp on or off, boot with or without the amp connected, and still get a correct display of my desktop environment on the netbook's LCD panel. I should add that this is using the proprietary fglrx driver.

KDE 4.13 (on Kubuntu 14.04) apparently tried to simplify management of an external screen (while still not supporting audio-only over HDMI). I no longer see an obvious setting to set a display to be a clone of another display (nor a checkbox for getting a mirrored output on both displays). The options to save a setting are gone too ... as is the documentation for the whole Display configuration panel. I presume that one can achieve cloning by dragging the source screen avatar onto the destination screen's avatar after setting both to the same resolution ... but after a reboot (or sometimes after a disconnect/reconnect of the external) the configuration tends to get reset, probably to some default.

Am I missing something (certain packages, for instance)? How is one supposed to achieve what I'm looking for with KDE 4.13? Alternatively, is there a possibility to activate audio out over HDMI without activating support for an external display?

Audio only should be supported over HDMI - the display preferences shouldn't have any influence over this. In System Settings > Multimedia > Phonon > Audio Hardware Setup, what options are available under the "Profile" drop down? (The HDMI entries should be there, regardless of whether the cable is connected or not).

The only possible explanation for this is if the HDMI audio connection was for some reason routed through the fglrx driver - in which case you probably need to convince fglrx to provide audio-only mode.

bcooksley wrote:The only possible explanation for this is if the HDMI audio connection was for some reason routed through the fglrx driver - in which case you probably need to convince fglrx to provide audio-only mode.

I cannot answer your first questions ATM (the netbook is busy under LMDE), but apparently I wasn't clear: I'm NOT using fglrx in the Kubuntu/KDE 4.13 install, but the radeon driver instead.

And from what I understand of the situation when booted into LMDE, both audio interfaces (HDMI out and the Realtek sound subsystem) use the snd_intel_hda driver:

Code: Select all

> lspci -vk
...
00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Wrestler [Radeon HD 6290] (prog-if 00 [VGA controller])
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, fast devsel, latency 0, IRQ 42
        Memory at e0000000 (32-bit, prefetchable) [size=256M]
        I/O ports at 4000 [size=256]
        Memory at f0400000 (32-bit, non-prefetchable) [size=256K]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Kernel driver in use: fglrx_pci

00:01.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Wrestler HDMI Audio
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, fast devsel, latency 0, IRQ 40
        Memory at f0444000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Kernel driver in use: snd_hda_intel
...
00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA) (rev 40)
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, slow devsel, latency 64, IRQ 16
        Memory at f0440000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 2
        Kernel driver in use: snd_hda_intel


Is there a way (through the SystemSettings/Multimedia interface) to force a re-scan of the available interfaces and clear out obsolete entries?

How it is done depends on whether your system is using Pulseaudio. If it uses Pulseaudio, then you need to clear ~/.pulse/ outside KDE (and without Pulseaudio running) otherwise you need to clear /var/tmp/kdecache-$USER/libphonon/

Back under Kubuntu/KDE 4.13, I do have a "Digital Stereo (HDMI) Output" profile under the Sound Card entry in SystemSettings/Multimedia/Audio and Video Settings/Audio Hardware Setup. But I get no sound when I deactivate the (virtual ) screen corresponding to the AV amp. Just as the sound cuts off when the X server's DPMS power saving mode kicks in.
BTW, I am using PulseAudio indeed with the gstreamer backend, because that's the choice that was made for me by the installer.

So how do I select the sort of clone mode that was available in 4.11.x?

Code: Select all

> lspci -vk
...
00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Wrestler [Radeon HD 6290] (prog-if 00 [VGA controller])
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, fast devsel, latency 0, IRQ 40
        Memory at e0000000 (32-bit, prefetchable) [size=256M]
        I/O ports at 4000 [size=256]
        Memory at f0400000 (32-bit, non-prefetchable) [size=256K]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Kernel driver in use: radeon

00:01.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Wrestler HDMI Audio
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, fast devsel, latency 0, IRQ 41
        Memory at f0444000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Kernel driver in use: snd_hda_intel
...
00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA) (rev 40)
        Subsystem: Acer Incorporated [ALI] Device 0598
        Flags: bus master, slow devsel, latency 64, IRQ 16
        Memory at f0440000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 2
        Kernel driver in use: snd_hda_intel


My guess is that this is a bug in the fglrx drivers - or a power saving feature - as the graphics card is ultimately handling the HDMI connection (the audio connection is merely routed through it).

As for the user interface - it should display all active displays and allow you to drag them to reposition them. If you drag the HDMI monitor over the main display, it should set it to clone mode. If the monitor hasn't appeared, you will likely need to use an xrandr command first to add the necessary resolution, etc.

But ... as I already repeated once, and as the 2nd lspci output shows, I'm NOT using fglrx under Kubuntu. So if there's a bug, it's in both the Radeon and in the fglrx drivers (as it exists on both my testing set-ups). Which is possible of course, but Occam's razor would suggest that the bug is actually in a common bit of code. Possibly the snd_intel_hda driver, as that's what both set-ups use for audio HDMI out?

I more or less deduced that one has to use a graphical method for setting a display as a clone of another, but as there is no explanation of this anywhere:
1) how does one set the external screen to be a clone of the internal -- by dragging the internal screen representation over the external screen, or by dragging the external screen over the internal?
2) Is this supposed to "stick" even when the external screen is connected only occasionally and generally not when rebooting/logging in?

KDE 4.11 had a "save default configuration" option the intent of which at least was clear; the current interface has become much poorer.

I indeed use xrandr to add the appropriate resolution to the external screen. Regardless and even with the cloning set up properly (as far as I can guess from the visual representation!!!):
*) when logging in with the AV amp connected, the login splash screen behaves as if there are 2 resolutions; specifically, the splash background image doesn't cover the whole screen
*) after disconnecting the AV amp the screensaver ("Clock") display gets messed up, exactly as if it's trying to display on 2 superposed displays of different resolution. I've seen this before under KDE 4.11 when I still cloned my internal 1366x768 screen to the AV amp at 1280x800 (before I had figured out the xrandr command).

Do I have to file bug reports, and if so, for what components?

Sorry - what I meant by fglrx there was "graphics driver". In terms of common - what is probable is that the snd_hda_intel driver relies on the graphics driver to "light up" the HDMI port - if it hasn't done this (or has turned it off) - then audio won't be sent.

In terms of the settings sticking - KScreen will remember the identifier of the external screen (the audio system in this case) and act appropriately next time it detects it (ie. device is plugged in / turned on). You'll need to ensure the appropriate resolution is available though - which might prove more tricky.

For the splash screen and screensaver - those are valid bugs. The components are probably "ksplash" and "kscreensaver" I suspect - on bugs.kde.org.

bcooksley wrote:Sorry - what I meant by fglrx there was "graphics driver". In terms of common - what is probable is that the snd_hda_intel driver relies on the graphics driver to "light up" the HDMI port - if it hasn't done this (or has turned it off) - then audio won't be sent.

Yes ... but shouldn't in that case the multimedia interface show the HDMI port as "grayed out"?

You'll need to ensure the appropriate resolution is available though - which might prove more tricky.

Not really, just invoke the proper xrandr magic in either a script executed when logging in, or in /etc/kde4/kdm/Xsetup .

The Multimedia interface can only show what Pulseaudio believes, which in turn is limited by what the driver understands. If Pulseaudio is not aware the driver is unable to actually send the data then it will show the device as present - and it will be shown as available by System Settings.

I assume it permits you to begin playing back audio with the device connected but no display enabled on the connection and no sound is produced by the sound system? In this case, is there anything in dmesg to indicate why it may be happening?

Makes sense.

I tried: neither dmesg nor any of the systemlogs nor even systemsettings (when launched from a command line) give any output when I dis/connect the amp, de/activated the corresponding display entry, or play the test sound (whether it sounds or not).

So yes, the HDMI output channel is available regardless whether the amp is connected and/or the corresponding display is activated; there just is no sound if conditions aren't right (just like when an amp is switched to a different input).

Another thing: on the 'layout' page that allows to check if the speakers are wired correctly, the 'front left' and 'front right' buttons only sound when the internal (Realtek) audio device is selected, never over HDMI.

The speakers test component relies on libcanberra and Pulseaudio I believe, so i'm not sure why they wouldn't be working - it is probably a bug in one of these components.

In terms of getting audio only mode working, please file a bug with the appropriate kernel folks to get the snd_hda_intel driver fixed - it probably needs to know more about the underlying HDMI interface.

bcooksley wrote:As for the user interface - it should display all active displays and allow you to drag them to reposition them. If you drag the HDMI monitor over the main display, it should set it to clone mode. If the monitor hasn't appeared, you will likely need to use an xrandr command first to add the necessary resolution, etc.

Thanks bcooksley for this suggestion, dragging my displays ontop of eachother mirrored my output. For everyone else that might want to mirror their displays using the gui but not know how, I think your description needs clarification: In the "Display Configuration" tool accessible from "System Settings" size each window icon to the same resolution and then drag your computer's display icon on top of the hdmi display icon

Yeah, so it's the one being dragged onto another display that sets the latter to a clone of itself. I would have guessed that you'd drag the display you wanted to be a mirror (the more usual term) onto the display you wanted it to be the mirror of.
The older interface with its drop-down menu was maybe less licked but also less ambiguous.