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

[Nicolas Dufresne]

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
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
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