python, appsrc, min-percent for need-data ignored

[Jan Martinek-2]

Hi everyone,

at first, I would like to thank Nicolas Dufresne for his help in my
previous post - for some reason I am unable to reply to his post.

Anyway, I ported my waveform-playing script to gstreamer-1.0. It works -
I can compute bytes and send them to the sound card. But the signal
'need-data' is raised when only last 4096 bytes are present in the
queue. Therefore, I need to take care of the data every 23 milliseconds:
4096/(44100*4) = 0.02322 s
In the meantime I want to plot a graph, which takes more time, the
buffer runs out of data and ugly jittering results.

The default queue size of appsrc is 200000, which is fine, but never
used. The signal 'need-data' could be called when the queue size is half
full

min-percent=50

but the "min-percent" parameter is ignored and "current-level-bytes" is
always zero (empty queue).

Is it a bug? The example script line 42 can safely be removed.

Thank you
Jan Martinek

--------
#!/usr/bin/python

import gi, signal, struct, time
gi.require_version('Gst', '1.0')
gi.require_version('Gtk', '3.0')
from gi.repository import GObject,Gtk
from gi.repository import Gst
from math import sin, pi

GObject.threads_init()
Gst.init(None)


class Sound:
     def __init__(self):
         self.samplecounter = 0
         signal.signal(signal.SIGINT, signal.SIG_DFL)
         self.player = Gst.parse_launch('''appsrc name=source
min-percent=50 ! capsfilter
caps=audio/x-raw,rate=44100,channels=2,format=S16LE ! pulsesink''')
         playersrc = self.player.get_by_name('source')
         playersrc.connect('need-data', self.needdata)
         self.player.set_state(Gst.State.PLAYING)
         Gtk.main()


     def sinuswave(self, nbytes):
         data = ''
         mul1 = 2*pi*440/44100
         mul2 = 2*pi*442/44100
         for i in range(nbytes//4):
             data += struct.pack('hh',
             32767*sin(self.samplecounter*mul1),
             32767*sin(self.samplecounter*mul2))
             self.samplecounter += 1
         return data

     def needdata(self, src, length):
         print "current-level-bytes",
src.get_property("current-level-bytes")
         print "min-percent", src.get_property("min-percent")
         data = self.sinuswave(length)
         print len(data), length
         src.emit('push-buffer', Gst.Buffer.new_wrapped(data))
         time.sleep(0.02322) # REMOVE ME TO GET A NICE SOUND

sa = Sound()
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[Nicolas Dufresne-5]

Le lundi 05 juin 2017 à 12:58 +0200, Jan Martinek a écrit :

> Hi everyone,
>
> at first, I would like to thank Nicolas Dufresne for his help in my 
> previous post - for some reason I am unable to reply to his post.
>
> Anyway, I ported my waveform-playing script to gstreamer-1.0. It
> works - 
> I can compute bytes and send them to the sound card. But the signal 
> 'need-data' is raised when only last 4096 bytes are present in the 
> queue. Therefore, I need to take care of the data every 23
> milliseconds:
> 4096/(44100*4) = 0.02322 s
> In the meantime I want to plot a graph, which takes more time, the 
> buffer runs out of data and ugly jittering results.

I do think that the length is just the block size (or the range in pull
mode). It's a hint over the expected data size. You should keep pushing
until enough-data is emitted. This is called in a re-entrant way,
within you call to "push-data". This will allow filling the queue, and
will make the threshold work.

>
> The default queue size of appsrc is 200000, which is fine, but never 
> used. The signal 'need-data' could be called when the queue size is
> half 
> full

>
> min-percent=50
>
> but the "min-percent" parameter is ignored and "current-level-bytes"
> is 
> always zero (empty queue).
>
> Is it a bug? The example script line 42 can safely be removed.
>
> Thank you
> Jan Martinek
>
> --------
> #!/usr/bin/python
>
> import gi, signal, struct, time
> gi.require_version('Gst', '1.0')
> gi.require_version('Gtk', '3.0')
> from gi.repository import GObject,Gtk
> from gi.repository import Gst
> from math import sin, pi
>
> GObject.threads_init()
> Gst.init(None)
>
>
> class Sound:
>      def __init__(self):
>          self.samplecounter = 0
>          signal.signal(signal.SIGINT, signal.SIG_DFL)
>          self.player = Gst.parse_launch('''appsrc name=source 
> min-percent=50 ! capsfilter 
> caps=audio/x-raw,rate=44100,channels=2,format=S16LE ! pulsesink''')
>          playersrc = self.player.get_by_name('source')
>          playersrc.connect('need-data', self.needdata)
>          self.player.set_state(Gst.State.PLAYING)
>          Gtk.main()
>
>
>      def sinuswave(self, nbytes):
>          data = ''
>          mul1 = 2*pi*440/44100
>          mul2 = 2*pi*442/44100
>          for i in range(nbytes//4):
>              data += struct.pack('hh',
>              32767*sin(self.samplecounter*mul1),
>              32767*sin(self.samplecounter*mul2))
>              self.samplecounter += 1
>          return data
>
>      def needdata(self, src, length):
>          print "current-level-bytes", 
> src.get_property("current-level-bytes")
>          print "min-percent", src.get_property("min-percent")
>          data = self.sinuswave(length)
>          print len(data), length
>          src.emit('push-buffer', Gst.Buffer.new_wrapped(data))
>          time.sleep(0.02322) # REMOVE ME TO GET A NICE SOUND
>
> sa = Sound()
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

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