bugger.py

#
# Playbin bug: Play 2 flac files (presumably of any length), and play
#              2 mp3 files, using gapless playback, and weirdness happens
#
# On GST 1.4.5, track4.mp3 stalls for ~10s or so without playing, but
# there is no audio for track3 or track4. Other tests I've conducted
# track3 does have audio, but there is still a pause.
#
# On GST 1.5.2, there is no volume for track3 or track4.mp3, but no
# stall occurs. Seems like a bug.
#
# Tested on Linux, probably using pulsesink as output.
#

from gi.repository import Gst, GObject, GLib, Gio

Gst.init(None)

playbin = Gst.ElementFactory.make('playbin')
playbin.props.volume = .2

uris = [
    'track1.flac',
    'track2.flac',
    'track3.mp3',
    'track4.mp3'
]

# Convert to uri
for i in range(len(uris)):
    uris[i] = Gio.File.new_for_commandline_arg(uris[i]).get_uri()


# Gapless playback mechanism
def on_about_to_finish(_):
    try:
        uri = uris.pop(0)
    except:
        ml.quit()
    else:
        print 'about to play', uri
        playbin.set_property('uri', uri)


playbin.connect('about-to-finish', on_about_to_finish)

# Print the current stream position every second
def query_pos():
    res, pos = playbin.query_position(Gst.Format.TIME)
    if res:
        print 'pos: %.02f' % (float(pos)/Gst.SECOND)
        
    return True

GLib.timeout_add(1000, query_pos)

# Originally, we noticed that the pipeline stall only happened
# when a seek occurred.
def do_skip():
    new_position = int(Gst.SECOND * 3)
    seek_event = Gst.Event.new_seek(1.0, Gst.Format.TIME,
        Gst.SeekFlags.FLUSH, Gst.SeekType.SET,
        new_position,
        Gst.SeekType.NONE, 0)
    
    playbin.send_event(seek_event)
    print 'seek!'
    
    return False

GLib.timeout_add(13000, do_skip)


# Start it up
on_about_to_finish(None)
playbin.set_state(Gst.State.PLAYING)

ml = GObject.MainLoop()
ml.run()

print 'Done'

track1.flac

track2.flac

track3.mp3

track4.mp3