In the ubuntu 20.04, we met an issue about the output volume-slider
on the machine with the legacy HDA audio driver, the output device
is the Speaker first (analog-stereo pa sink), then we connect a hdmi
monitor, the HDMI audio is in the output combo-box, we select the
hdmi audio (hdmi-stereo pa sink) from the combo-box, the hdmi audio
becomes the active output device now, we adjust the output volume from
the volume-slider, the slider UI is changed, but the output sound
is not changed with the UI.
The root cause is when the speaker is active, the pulseaudio only
keeps the analog-stereo sink, the sink hdmi-stereo is unlinked, when
users select the hdmi audio from UI, the pulseaudio will unlink
analo-stereo sink and create hdmi-stereo sink, but before hdmi-stereo
is created, the output_device_changed_cb() is called and
gvc_mixer_control_get_stream_from_device() returns a NULL since the
hdmi-stereo sink is not created yet in the pulseaudio. Because stream
is NULL, the output_volume_slider->stream is NULL, users can't change
the output volume via the volume-slider.
To fix it, we add a output_volume_slider->stream check in the
device_update_cb(), if it is NULL, get the stream and set it to
volume-slider. In this function, the sink hdmi-stereo is created
already, so the stream is not NULL. And this change also applies to
input as well.
Signed-off-by: Hui Wang <hui.wang@canonical.com>
0f18a662be