[pulseaudio-discuss] [PATCH] module: new null-source module

David Henningsson david.henningsson at canonical.com
Wed Apr 27 07:55:40 PDT 2011

On 2011-04-27 15:18, Colin Guthrie wrote:
> 'Twas brillig, and Tanu Kaskinen at 27/04/11 12:59 did gyre and gimble:
>> On Wed, 2011-04-27 at 14:50 +0300, Tanu Kaskinen wrote:
>>> From: Marc-André Lureau<marcandre.lureau at gmail.com>
>>> ---
>>>   src/Makefile.am                  |    6 +
>>>   src/modules/module-null-source.c |  294 ++++++++++++++++++++++++++++++++++++++
>>>   2 files changed, 300 insertions(+), 0 deletions(-)
>>>   create mode 100644 src/modules/module-null-source.c
>> This module isn't actually used by anyone currently. We (at Nokia)
>> switched to null-sink's monitor a long time ago (for reasons unknown to
>> me), so the code hasn't had much testing lately. Even though there are
>> no users for the module currently, I'm sending the patch anyway, just in
>> case people think that the module might be useful in some situation.
>> I quickly tested that I can record silence with parec from source.null -
>> I can't give any further guarantees that the code is correct.
> Yeah due to the fact that a null sink has a null monitor, this module is
> of limited usefulness, but I think it could still be useful in some
> cases where you do want a null recording but don't want it polluted with
> sinks.
> I did actually have someone that wanted to hook up null sources and null
> sinks to some Windows VMs a while back (several VMs but only one null
> sink+monitor source). He was annoyed that he could record other VMs
> output from within a separate VM on the monitor. Obviously he can
> shuffle around the various streams and create multiple null sinks but it
> would have actually been simpler to setup a null source in the first place.
> So I'll do some testing then grab it at some point (tho' need to spend
> some time reviewing Margarita's work before next week otherwise Liam and
> Mark will find some way to punish me!)

FYI, I've done some review of that code already, and I agree with 
plbossart's comments recently about the jack detection being done the 
wrong way.

In addition, I don't think we (as in Canonical/Ubuntu) even got it to 
work yet even though we've tried it several times. You can see some of 
it here: https://bugs.launchpad.net/ubuntu/+source/alsa-lib/+bug/746023

So I don't think it's ready. The question about how we can make it ready 
might be a topic for next week's conference perhaps. See you!

David Henningsson, Canonical Ltd.

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