Cannot parse SDP message in python demo

[vhdirk]

The function SDPMessage.new_from_text does not exist in my case?

res, sdpmsg = GstSdp.SDPMessage.new_from_text(sdp)

What python version is this using? On my system I have python3-gst-1.0 1.14.1-1 (from debian buster)

[sdroege]

This was just added in GIT master: https://bugzilla.gnome.org/show_bug.cgi?id=796563

It should use the old way in the demos IMHO, want to send a PR? Old way is

    res, msg = GstSdp.SDPMessage.new()
    GstSdp.sdp_message_parse_buffer(bytes(text.encode()), msg)

[vhdirk]

I tried that already, but it's greeting me with a good old:

free(): invalid pointer

[sdroege]

Can you get a backtrace for that, or even better run in valgrind?

@MathieuDuponchelle, any ideas?

[vhdirk]

Here's backtrace gotten from gdb:

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffeb0a8700 (LWP 1034)]
[New Thread 0x7fffea433700 (LWP 1036)]
[New Thread 0x7fffe2d37700 (LWP 1039)]
application/x-gst-promise, offer=(GstWebRTCSessionDescription)NULL;
[New Thread 0x7fffe2536700 (LWP 1040)]
[New Thread 0x7fffe1d35700 (LWP 1041)]
[New Thread 0x7fffe1534700 (LWP 1042)]
[New Thread 0x7fffe0d33700 (LWP 1043)]
[New Thread 0x7fffc7fff700 (LWP 1044)]
Sending offer:
v=0
o=- 5987065807280142380 0 IN IP4 0.0.0.0
s=-
t=0 0
a=ice-options:trickle
m=video 9 UDP/TLS/RTP/SAVPF 97
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:R658jYZB94Yh7oCb8gOS1TBG/YxL+j+Z
a=ice-pwd:CaTpJcYIJRQFS/hr2IwydfmuiLp8wthT
a=sendrecv
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:97 VP8/90000
a=rtcp-fb:97 nack
a=rtcp-fb:97 nack pli
a=mid:video0
a=fingerprint:sha-256 48:F5:B7:AA:35:38:E8:81:93:7B:10:F1:BE:74:8D:54:EB:8C:51:ED:4D:9B:84:D2:88:4A:EC:B7:7D:7C:2E:00
m=audio 9 UDP/TLS/RTP/SAVPF 96
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:45tgI956BdVyxu5XNh/rnvDGpPrB+dJR
a=ice-pwd:G4d5/HwQkKp56NwiHl3rhdYZzl6k58oF
a=sendrecv
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 OPUS/48000/2
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=mid:audio1
a=fingerprint:sha-256 48:F5:B7:AA:35:38:E8:81:93:7B:10:F1:BE:74:8D:54:EB:8C:51:ED:4D:9B:84:D2:88:4A:EC:B7:7D:7C:2E:00

[New Thread 0x7fffc77fe700 (LWP 1045)]
[New Thread 0x7fffc6ffd700 (LWP 1046)]
[New Thread 0x7fffc67fc700 (LWP 1047)]
[New Thread 0x7fffc5ffb700 (LWP 1048)]
[New Thread 0x7fffc57fa700 (LWP 1049)]
[New Thread 0x7fffc4ff9700 (LWP 1050)]
[New Thread 0x7fffa7fff700 (LWP 1051)]
[New Thread 0x7fffa77fe700 (LWP 1052)]
[New Thread 0x7fffa6ffd700 (LWP 1053)]
[New Thread 0x7fffa67fc700 (LWP 1055)]
[New Thread 0x7fffa5ffb700 (LWP 1056)]
[New Thread 0x7fffa57fa700 (LWP 1057)]
Received answer:
v=0
o=- 6985988093201023069 2 IN IP4 127.0.0.1
s=-
t=0 0
a=msid-semantic: WMS ly0KJHm5lAKSkd5wtXcjBNUKpD0msAE4Gsav
m=video 9 UDP/TLS/RTP/SAVPF 97
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:bFQw
a=ice-pwd:91LZHOmu/Zah2EPfBgFKQx6N
a=ice-options:trickle
a=fingerprint:sha-256 C0:23:E9:54:40:53:BF:C5:E0:59:D2:1C:20:FB:69:18:CD:C0:A9:54:C7:0B:8B:BA:81:09:44:85:54:3E:0A:CC
a=setup:active
a=mid:video0
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:97 VP8/90000
a=rtcp-fb:97 nack
a=rtcp-fb:97 nack pli
m=audio 9 UDP/TLS/RTP/SAVPF 96
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:RfF1
a=ice-pwd:DOk77RF7t4EgtGJSdXqWJy8b
a=ice-options:trickle
a=fingerprint:sha-256 C0:23:E9:54:40:53:BF:C5:E0:59:D2:1C:20:FB:69:18:CD:C0:A9:54:C7:0B:8B:BA:81:09:44:85:54:3E:0A:CC
a=setup:active
a=mid:audio1
a=sendrecv
a=rtcp-mux
a=rtpmap:96 OPUS/48000/2
a=fmtp:96 minptime=10;useinbandfec=1
a=ssrc:1030008169 cname:Y6OCWD9JWJc4H+RE
a=ssrc:1030008169 msid:ly0KJHm5lAKSkd5wtXcjBNUKpD0msAE4Gsav f452f26f-8970-4218-86f0-20060d4fc7a1
a=ssrc:1030008169 mslabel:ly0KJHm5lAKSkd5wtXcjBNUKpD0msAE4Gsav
a=ssrc:1030008169 label:f452f26f-8970-4218-86f0-20060d4fc7a1

double free or corruption (out)

Thread 1 "python3" received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007ffff6c4ae7b in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff6c4c231 in __GI_abort () at abort.c:79
#2  0x00007ffff6c8d7b7 in __libc_message (action=action@entry=do_abort, fmt=fmt@entry=0x7ffff6d960f3 "%s\n") at ../sysdeps/posix/libc_fatal.c:181
#3  0x00007ffff6c93d5a in malloc_printerr (str=str@entry=0x7ffff6d97de0 "double free or corruption (out)") at malloc.c:5350
#4  0x00007ffff6c95810 in _int_free (av=0x7ffff6fcac40 <main_arena>, p=0x114def0, have_lock=<optimized out>) at malloc.c:4278
#5  0x00007ffff17f4918 in gst_sdp_message_init () at /usr/lib/x86_64-linux-gnu/libgstsdp-1.0.so.0
#6  0x00007ffff17f4d72 in gst_sdp_message_uninit () at /usr/lib/x86_64-linux-gnu/libgstsdp-1.0.so.0
#7  0x00007ffff17f4e8e in gst_sdp_message_free () at /usr/lib/x86_64-linux-gnu/libgstsdp-1.0.so.0
#8  0x00007ffff13a05b2 in gst_webrtc_session_description_free () at /usr/lib/x86_64-linux-gnu/libgstwebrtc-1.0.so.0
#9  0x00007ffff3fed01b in g_boxed_free () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#10 0x00007ffff44d70d0 in  () at /usr/lib/python3/dist-packages/gi/_gi.cpython-36m-x86_64-linux-gnu.so
#11 0x0000000000563caa in _PyCFunction_FastCallDict ()
#12 0x000000000058f971 in _PyObject_FastCallDict ()
#13 0x0000000000613843 in  ()
#14 0x000000000055e3e5 in PyObject_CallFinalizerFromDealloc ()
#15 0x0000000000534537 in  ()
#16 0x000000000056fb18 in  ()
#17 0x0000000000585a92 in  ()
#18 0x00000000004f1c20 in _PyEval_EvalFrameDefault ()
#19 0x0000000000585968 in  ()
#20 0x00007ffff4d68ea9 in  () at /usr/lib/python3.6/lib-dynload/_asyncio.cpython-36m-x86_64-linux-gnu.so
#21 0x000000000058f30e in PyObject_Call ()
#22 0x00000000004f1a34 in _PyEval_EvalFrameDefault ()
#23 0x000000000050b495 in  ()
#24 0x000000000050c14d in  ()
#25 0x00000000004f05f9 in _PyEval_EvalFrameDefault ()
#26 0x000000000050b495 in  ()
#27 0x000000000050c14d in  ()
#28 0x00000000004f05f9 in _PyEval_EvalFrameDefault ()
#29 0x000000000050b495 in  ()
#30 0x000000000050c14d in  ()
#31 0x00000000004f05f9 in _PyEval_EvalFrameDefault ()
#32 0x000000000050b495 in  ()
#33 0x000000000050c14d in  ()
#34 0x00000000004f05f9 in _PyEval_EvalFrameDefault ()
#35 0x00000000004ee787 in  ()
#36 0x00000000004efe73 in PyEval_EvalCode ()
#37 0x0000000000637b92 in  ()
#38 0x0000000000637c4a in PyRun_FileExFlags ()
#39 0x0000000000639bf8 in PyRun_SimpleFileExFlags ()
#40 0x000000000062b8fa in Py_Main ()
#41 0x00000000004b2790 in main ()

[sdroege]

That's fixed by https://cgit.freedesktop.org/gstreamer/gst-plugins-bad/commit/gst-libs/gst/webrtc/rtcsessiondescription.c?id=0178354e6e8598ab14091103db832e23ee1bdfcc and will be in 1.14.2.

@MathieuDuponchelle can we work around that on the Python side?

[vhdirk]

When is that due?
Since this is purely documentation, I would only have to regenerate the python bindings?

[sdroege]

You have to change the GstWebRTC-1.0.gir file for that function and then also regenerate the .typelib file with gobject-introspection.

[sdroege]

When is that due?

Probably next week

[MathieuDuponchelle]

@sdroege , there's no workaround I can think of no, if it was a (mini)object the refcount could be manipulated from python but that's not the case :(

[sdroege]

Ok so then this should be documented in the repository :)

[MathieuDuponchelle]

It is: 9a26415 ;)

[sdroege]

Ok so what has to be done here still is to not use the new API from master (or get it backported for 1.14.2) and then document that 1.14.2 is needed for the Python example. Seems suboptimal to require GIT master :)

[MathieuDuponchelle]

Closing manually, this is addressed