[pulseaudio-discuss] Profile switching on headphone plugging

[Alexander E. Patrakov]

07.02.2015 10:22, Raymond Yau wrote:
>
> >
> >> Hrm, that is actually a good question. In theory, I would expect
> >> module-switch-on-port-available to switch profiles between 2.0 and 2.1
> >> as headphones are plugged in and out, but in practice,
> >>
> >>   - I'm not 100% sure if our "don't switch to HDMI" might prevent
> >> switching from 2.1 to 2.0 when headphones are plugged in, and
> >>
> >>   - As the 2.0 profile is available on speakers, that will continue to
> >> be selected when headphones are unplugged.
> >>
> >> So, while this is not directly related to whether there is an LFE 
> filter
> >> or not - we already have a 2.1, 5.1, etc, profiles - indeed the problem
> >> might become worse with the LFE filter.
> >
> >
> > Well, I have just tested how today's git version of pulseaudio 
> (without your patch) behaves when plugging headphones. Yes - the 
> problem is pre-existing.
> >
> > The PC under test has analog outputs on the back panel that, 
> theoretically, can be used as analog 5.1 outputs, and also has 
> headphone and microphone sockets at the front panel.
> >
> > So, the test is:
> >
> > 1. Make sure something (I tested with a cable extender) is plugged 
> in the line output on the back panel.
> > 2. Select the "analog stereo duplex" profile in pavucontrol.
> > 3. Look at the Playback devices tab. It should say: Port: Line Out 
> (plugged in).
> > 4. Plug in headphones at the front. Note that the port changes to: 
> Headphones (plugged in). I.e. exactly as expected.
> > 5. Unplug the headphones, watch how the port changes back to Line 
> Out (plugged in).
> > 5. Now select the Analog Surround 5.1 + Stereo Input as a profile. 
> Now the port stays as Line Out (plugged in), but the volume control 
> becomes 6-channel.
> > 6. Plug headphones in. Result: the port stays as Line Out (plugged 
> in), with 6-channel volume control, and speaker-test -c6 does not 
> reach headphones.
> >
> > Sorry, I cannot retest this at home without additional 
> jack-retasking (which could make the result untrustworthy), because my 
> home PC does not have any audio sockets at the front panel.
> >
>
> I have doubt about changing 5.1 profile to stereo when headphone is 
> plugged since most user use 5.1 profile to watch movie, changing 5.1 
> profile to stereo require stop playback of 5.1 and start stereo 
> playback , how can the application perform video audio sync for this 
> kind of profile switching
>

It is not the job of the application to react to this. PulseAudio can 
downmix 5.1 to stereo just fine. Besides, such switching of the number 
of channels already happens when the user moves the audio stream from 
the movie player from 5.1 HDMI sink of his video card to the built-in 
stereo audio. So - no reason to worry at all.

No comments about the questions in the remainder of your email, because 
I am not sure I understand them correctly.

-- 
Alexander E. Patrakov