[gst-devel] Segfault when using callbacks in gst-python for buffer retrieval
Matthias Blaicher
blaicher at googlemail.com
Fri Aug 29 15:01:02 CEST 2008
Hallo together,
I'm working on a project which requires me to to buffer frames from a
video4linux source in Python. I decided that gstreamer is perfectly
fit for such a task and have already tried some initial code - Which
all fail in a non spectacular segfault.
Here is what I'm trying to do:
I have such a path:
v4lsrc ! video/x-raw-yuv,width=640,height=480 ! ffmpegcolorspace !
pngenc snapshot=False ! fakesink name=sink
Which should generate a continuous stream of png frames. Now i try to
intercept the exchanged Buffer objects by using the handoff event of
fakesink with a callback. But whenever I activate the callback, the
python interpreter dies with a segmentation fault. I also tried to
intercept the Buffers with the Pad.add_buffer_probe call, but that
fails the same way.
My code is:
import gst
import time
gst.debug_set_active(True)
gst.debug_set_default_threshold(4)
def callback(fakesink, buffer, pad, data=None):
return True
def probe_callback_fakesrc(pad, buffer):
return True
#v4lsrc
pipeline = gst.parse_launch('videotestsrc !
video/x-raw-yuv,width=640,height=480 ! ffmpegcolorspace ! pngenc
snapshot=False ! fakesink name=sink')
fakesink = pipeline.get_by_name('sink')
# Way 1
fakesink.props.signal_handoffs = True
fakesink.connect("handoff", callback)
## Way 2
#pad = fakesink.get_pad('sink')
#pad.add_buffer_probe(probe_callback_fakesrc)
pipeline.set_state(gst.STATE_PLAYING)
while True:
#Sleep so that context switching for gst works
time.sleep(1)
Which fails such as (with debug leve 4 and strace)
0:00:04.553704144 9029 0x832f1d8 INFO GST_STATES
gstelement.c:2148:gst_element_continue_state:<sink> completed state
change to PLAYING
0:00:04.553717205 9029 0x832f1d8 INFO GST_STATES
gstelement.c:2161:gst_element_continue_state:<sink> posting
state-changed PAUSED to PLAYING
0:00:04.553714760 9029 0x8325750 DEBUG basesink
gstbasesink.c:1508:gst_base_sink_wait_preroll:<sink> continue after
preroll
0:00:04.553743117 9029 0x8325750 DEBUG basesink
gstbasesink.c:1678:gst_base_sink_do_sync:<sink> possibly waiting for
clock to reach 0:00:00.000000000
0:00:04.553763652 9029 0x8325750 DEBUG basesink
gstbasesink.c:1468:gst_base_sink_wait_clock:<sink> sync disabled
0:00:04.553784466 9029 0x8325750 DEBUG basesink
gstbasesink.c:1684:gst_base_sink_do_sync:<sink> clock returned 4
0:00:04.553798993 9029 0x8325750 DEBUG basesink
gstbasesink.c:2029:gst_base_sink_render_object:<sink> rendering buffer
0x8328e68
0:00:04.553789634 9029 0x832f1d8 DEBUG GST_BUS
gstbus.c:337:gst_bus_post:<bus0> [msg 0x83321d0] posting on bus, type
state-changed, GstMessageState, old-state=(GstState)GST_STATE_PAUSED,
new-state=(GstState)GST_STATE_PLAYING,
pending-state=(GstState)GST_STATE_VOID_PENDING; from source <sink>
0:00:04.553835034 9029 0x832f1d8 DEBUG bin
gstbin.c:2719:gst_bin_handle_message_func:<pipeline0> [msg 0x83321d0]
handling child sink message of type state-changed
0:00:04.553848933 9029 0x832f1d8 DEBUG bin
gstbin.c:2923:gst_bin_handle_message_func:<pipeline0> posting message
upward
0:00:04.553862133 9029 0x832f1d8 DEBUG GST_BUS
gstbus.c:337:gst_bus_post:<bus1> [msg 0x83321d0] posting on bus, type
state-changed, GstMessageState, old-state=(GstState)GST_STATE_PAUSED,
new-state=(GstState)GST_STATE_PLAYING,
pending-state=(GstState)GST_STATE_VOID_PENDING; from source <sink>
0:00:04.553889303 9029 0x832f1d8 DEBUG GST_BUS
gstbus.c:367:gst_bus_post:<bus1> [msg 0x83321d0] pushing on async
queue
0:00:04.553887906 9029 0x8325750 DEBUG pygst
pygstminiobject.c:152:pygstminiobject_new: have to create wrapper for
object 0x8328e68
0:00:04.553904041 9029 0x832f1d8 DEBUG GST_BUS
gstbus.c:372:gst_bus_post:<bus1> [msg 0x83321d0] pushed on async queue
0:00:04.553913679 9029 0x8325750 DEBUG pygst
pygstminiobject.c:171:pygstminiobject_new: created Python object
0xb7ddc800 for GstMiniObject 0x8328e68 [ref:4]
0:00:04.553917870 9029 0x832f1d8 DEBUG GST_BUS
gstbus.c:363:gst_bus_post:<bus0> [msg 0x83321d0] dropped
0:00:04.553937357 9029 0x832f1d8 DEBUG GST_STATES
gstelement.c:2380:gst_element_set_state_func:<sink> returned SUCCESS
) = ? ERESTARTNOHAND (To be restarted)
+++ killed by SIGSEGV +++
Process 9029 detached
I use Ubuntu Hardy with gst.version() == (0, 10, 18, 0)
Does anybody know what I'm doing wrong here?
Sincerely,
Matthias Blaicher
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