[pulseaudio-discuss] Audio APP (sink-input) bind to the sink with only unplugged hdmi-audio ports on it

[Tanu Kaskinen]

On Sun, 2018-09-30 at 15:03 +0800, Hui Wang wrote:
> This issue is also reported to: 
> https://gitlab.freedesktop.org/pulseaudio/pulseaudio/issues/579
> 
> Recently we found a weird issue on many laptops with the ubuntu 18.04, 
> it uses the pulseaudio-11.1 (I guess the PA of the latest version also 
> has this problem). The issue is like this:
> 
>  1. boot the system up without plugging a hdmi monitor
>  2. run an audio app to play sound (e.g. $speaker-test)
>  3. the sound outputs from analog-speaker
>  4. plug a monitor with audio capability (through DP or HDMI port)
>  5. the sound still outputs from analog-speaker
>  6. open sound-setting (gnome-control-center --> choose sound), you will
>     see two output devies: speaker and HDMI audio
>  7. choose HDMI audio, the sound will switch to HDIM audio from speaker
>     (pa will remember speaker-test prefer to use hdmi-audio sink)
>  8. unplug the monitor, the default-sink is switching to analog-speaker,
>     but the sound of speaker-test still route to hdmi-audio sink
>  9. run other sound apps, they all route sound to default sink
>     (analog-speaker), but speaker-test always routes to hdmi-audio sink,
>     as a result, speaker-test can't output sound anymore unless we
>     replug a monitor with audio capability then the speaker-test output
>     from hdmi-audio again.
> 10. if we want the speaker-test to route to analog-speaker, two ways:
>     run pacmd move-sink-input or plug a monitor, after two audio devices
>     (hdmi audio and speaker) show up in the sound-setting, select
>     analog-speaker manually.
> 
> This issue only happens on the laptops with 2 audio cards, analog 
> devices on one card, hdmi audio on the other card. This kind of laptops 
> are very common, like I+A (Intel graphic + Amd Graphic), I+N(Intel + 
> Nvidia), and A AMD.
> 
> This issue will not happen on the laptops with only Intel graphic card, 
> since both analog and hdmi audio belong to one sound card. When hdmi 
> monitor is unplugged, the hdmi sink will be removed from PA, then all 
> sink-inputs will route to the only left sink: analog-sink.
> 
> This issue will not happen on BT or USB audio. Unlike hdmi audio, BT and 
> USB audio cards will be removed totally from PA when they are 
> unpluged/unconnected, so they don't have this issue as well.
> 
> The root cause of this issue is although the hdmi monitor is unplugged, 
> the hdmi-sink still exists, and sink-input is selected by user to bind 
> to this sink, so the pa doesn't care about if this sink has valid port 
> or not, it bind the sink-input to this sink unconditionally.
> 
> Maybe we could improve it like this: if the user selected sink only has 
> available_no ports, the pa will switch all sink-inputs of this sink to 
> other sinks (like default_sink) temporarily, once the selected sink has 
> availble ports, all sink-inputs switch back to this sink.
> 
> Any good ideas?

The plan has been to do the following (but I haven't found the time to
implement it):

Streams currently have a "save_sink" flag that tells whether the
current sink should be remembered and restored by module-stream-
restore. That flag should be replaced with a "preferred_sink" string
that is set when the user moves the stream. module-stream-restore
should remember and restore that string.

When the user moves a stream to the current default sink, the
"preferred_sink" string should be set to NULL and module-stream-restore 
should clear the routing for that stream in the stream database. From
that point on the stream will be always routed to the default sink.

When a stream is created, module-stream-restore should set the
"preferred_sink" string and if that sink exists, the core should set
that sink as the initial routing for the new stream.

When the default sink changes, the streams from the old default sink
should be moved to the new default sink, unless the "preferred_sink"
string is set to the old default sink and the active port of the old
default sink is not unavailable. This should be done by the core.

When the active port of a sink becomes unavailable, all streams from
that sink should be moved to the default sink. This should be done by
the core.

When a new sink appears or the active port of an existing sink changes
state from unavailable, all streams that have their "preferred_sink"
set to the new sink should be moved to the new sink. This should be
done by the core.

As a result, module-stream-restore doesn't need to move streams any
more, it only needs to manage the "preferred_sink" variables. Some
other modules can perhaps be simplified as well.

The same logic should of course be implemented for capture streams as
well.

Would you be willing to implement this?

-- 
Tanu

https://www.patreon.com/tanuk
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