I've been reading up and experimenting on both the simple and async
APIs. In one experiment, I used a CLI file that sets up a set of
module-sine modules with output remapped by module-remap-sink modules
to a stream fed to a module-null-sink module.
I then wrote 2 programs, one using the simple API and the other the
async API to read date from the module-null-sink monitor source and
write the data to file (both based on examples to provide "parec"
functionality). Then I could unload either all the module-sine
modules or all the module-remap-sink modules to interrupt the data
source to the module-null-sink module.
Both programs gave the same result, which I don't completely understand.
The issues I've found are:
1. After the data source is gone, the program continues to write data
to file. There doesn't seem to be any way to detect a stream of
"zero" data using the APIs.
That is expected behavior. null-sink.monitor is not different from other
sources, which means
if there is no input to the null-sink, it will generate silence. It's
like recording from an unplugged
mic or line-in input.
And there's no silence detection?
2. If I run it for 20 seconds, with 10 seconds of sinusoidal data
followed by 10 seconds of null data, the file ends up with anything
from 30 to 40 seconds worth of data in it.
3. The files written from case 2, above, show the initial sinusoidal
data as expected, but then, following data stream interruption, about
5 to 10 seconds of switching back and forth between segments of
sinusoidal data and null data, before finally settling to null data
only till the end of file.
Did you test if the same happens with parec? If yes, are there any log
messages
during the time?
Just did it and the result is the same. Attached is the relevant part
of the syslog.
Can anyone explain to me why it behaves like this? Or if there's
something in the async API that I'm missing in detecting null data?
May 19 12:18:21 walnut02 pulseaudio[6305]: GetManagedObjects() failed:
org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes
include: the remote application did not send a reply, the message bus security
policy blocked the reply, the reply timeout expired, or the network connection
was broken.
May 19 12:18:28 walnut02 gnome-session[3836]: (Audacity:6319): Gtk-WARNING **:
gtk_disable_setlocale() must be called before gtk_init()
May 19 12:18:29 walnut02 gnome-session[3836]: ALSA lib
pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
May 19 12:18:29 walnut02 gnome-session[3836]: ALSA lib
pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
May 19 12:18:29 walnut02 gnome-session[3836]: ALSA lib
pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
May 19 12:18:29 walnut02 gnome-session[3836]: ALSA lib
pcm_route.c:867:(find_matching_chmap) Found no matching channel map
May 19 12:18:29 walnut02 gnome-session[3836]: Cannot connect to server socket
err = No such file or directory
May 19 12:18:29 walnut02 gnome-session[3836]: Cannot connect to server request
channel
May 19 12:18:29 walnut02 gnome-session[3836]: jack server is not running or
cannot be started
May 19 12:18:29 walnut02 gnome-session[3836]:
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295,
skipping unlock
May 19 12:18:29 walnut02 gnome-session[3836]:
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for 4294967295,
skipping unlock
May 19 12:18:29 walnut02 gnome-session[3836]: Expression 'stream->playback.pcm'
failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 4611
May 19 12:18:29 walnut02 gnome-session[3836]: message repeated 4 times: [
Expression 'stream->playback.pcm' failed in 'src/hostapi/alsa/pa_linux_alsa.c',
line: 4611]
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'click/left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'drag', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'click', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'right'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'click', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'click/left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'drag', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'left'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'click', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unknown accel
modifier: 'right'
May 19 12:18:29 walnut02 gnome-session[3836]: 12:18:29: Debug: Unrecognized
accel key 'click', accel string ignored.
May 19 12:18:29 walnut02 gnome-session[3836]: (Audacity:6319): Gdk-CRITICAL **:
IA__gdk_window_get_origin: assertion 'GDK_IS_WINDOW (window)' failed
May 19 12:18:29 walnut02 gnome-session[3836]: message repeated 51 times: [
(Audacity:6319): Gdk-CRITICAL **: IA__gdk_window_get_origin: assertion
'GDK_IS_WINDOW (window)' failed]
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