我正在将Gstreamer 1.0与Python绑定一起使用。 以下是考虑使用Opengl plugins时要构建的管道：
gltestsrc -> gltransformation -> glimagesink
我正在尝试根据从外部硬件设备收到的值来动态修改元素'gltransformation'的属性。这是link，用于类似的问题，但在用例中并没有太大帮助。 以下是python脚本的片段：
import gi
gi.require_version('Gst','1.0')
from gi.repository import Gst,GstController
#global variables
#the values of a,b,c get updated for certain events dynamically based on external hardware
a = 0
b= 0
c = 0
source = Gst.ElementFactory.make("gltestsrc", "source")
gltrnsfrm = Gst.ElementFactory.make("gltransformation","gltrnsfrm")
sink = Gst.ElementFactory.make("glimagesink", "sink")
# create the empty pipeline
pipeline = Gst.Pipeline.new("test-pipeline")
if not pipeline or not source or not gltrnsfrm or not sink:
print("ERROR: Not all elements could be created")
sys.exit(1)
# build the pipeline
pipeline.add(source,gltrnsfrm,sink)
if not source.link(gltrnsfrm):
print("ERROR: Could not link source to gltrsnfrm")
sys.exit(1)
if not gltrnsfrm.link(sink):
print("ERROR: Could not link gltrsnfrm to sink")
sys.exit(1)
# modify the gltransformation's properties
gltrnsfrm.set_property("rotation-z",a)
gltrnsfrm.set_property("rotation-x",b)
gltrnsfrm.set_property("rotation-y",c)
#dynamic controller
cs = GstController.InterpolationControlSource()
cs.set_property('mode', GstController.InterpolationMode.LINEAR)
cb= Gstcontorller.DirectControlBinding.new(gltrnsfrm,"rotation-x",cs)
gltrnsfrm.add_control_binding(cb)
#modify the values
cs.set(0*Gst.SECOND,b) #use updated values of b
cs.set(1*Gst.SECOND,b)
上面的示例仅显示了1个元素属性的修改，但是，我还有其他属性也要根据a,b & c的值进行修改。
执行上述脚本会给我以下错误：
GStreamer-CRITICAL : gst_object_add_control_binding: assertion 'binding->pspec' failed.
我想我必须在python中设置更多的属性才能正常工作。 有人在这个问题上有帮助吗？
编辑： 根据休·费舍尔（Hugh Fisher）的建议，我试图追溯到文件的源头。这是original code的摘要：
GST_INFO_OBJECT (object, "trying to put property '%s' under control",
binding->name);
/* check if the object has a property of that name */
if ((pspec =
g_object_class_find_property (G_OBJECT_GET_CLASS (object),
binding->name))) {
GST_DEBUG_OBJECT (object, " psec->flags : 0x%08x", pspec->flags);
/* check if this param is witable && controlable && !construct-only */
if ((pspec->flags & (G_PARAM_WRITABLE | GST_PARAM_CONTROLLABLE |
G_PARAM_CONSTRUCT_ONLY)) ==
(G_PARAM_WRITABLE | GST_PARAM_CONTROLLABLE)) {
binding->pspec = pspec;
} else {
GST_WARNING_OBJECT (object,
"property '%s' on class '%s' needs to "
"be writeable, controlable and not construct_only", binding->name,
G_OBJECT_TYPE_NAME (object));
}
} else {
GST_WARNING_OBJECT (object, "class '%s' has no property '%s'",
G_OBJECT_TYPE_NAME (object), binding->name);
}
gst_object_unref (object);
这是我的脚本的日志文件：
0:00:00.174410648 [336m 8309[00m 0xd1b750 [37mTRACE [00m [00;01;31;44m GST_REFCOUNTING gstobject.c:207:gst_object_init:<GstObject@0x10b0020>[00m 0x10b0020 new
0:00:00.174697421 [336m 8309[00m 0xd1b750 [37mTRACE [00m [00;01;31;44m GST_REFCOUNTING gstobject.c:207:gst_object_init:<GstObject@0x10b20f0>[00m 0x10b20f0 new
0:00:00.174716708 [336m 8309[00m 0xd1b750 [36mINFO [00m [00m gstcontrolbinding gstcontrolbinding.c:144:gst_control_binding_constructor:<gltrnsfrm>[00m trying to put property 'rotation-x' under control
0:00:00.174723927 [336m 8309[00m 0xd1b750 [37mDEBUG [00m [00m gstcontrolbinding gstcontrolbinding.c:150:gst_control_binding_constructor:<gltrnsfrm>[00m psec->flags : 0x000000e3
0:00:00.174729088 [336m 8309[00m 0xd1b750 [33;01mWARN [00m [00m gstcontrolbinding gstcontrolbinding.c:161:gst_control_binding_constructor:<gltrnsfrm>[00m property 'rotation-x' on class 'GstGLTransformation' needs to be writeable, controlable and not construct_only
0:00:00.174733951 [336m 8309[00m 0xd1b750 [37mTRACE [00m [00;01;31;44m GST_REFCOUNTING gstobject.c:264:gst_object_unref:<gltrnsfrm>[00m 0x10a60e0 unref 4->3
(python3:8309): GStreamer-CRITICAL **: 10:37:00.609: gst_object_add_control_binding: assertion 'binding->pspec' failed
根据“ gltransformation”的手册页，属性rotation-x / y / z可写且可读。这里还有一个link应用程序，它从GUI接收输入并更改“ gltransformation”的旋转x / y / z。 我不知道，为什么就我而言这是一个问题。
#gst-inspect-1.0 gltransformation
translation-x : Translates the video at the X-Axis, in universal [0-1] coordinate.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
translation-y : Translates the video at the Y-Axis, in universal [0-1] coordinate.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
translation-z : Translates the video at the Z-Axis, in universal [0-1] coordinate.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
rotation-x : Rotates the video around the X-Axis in degrees.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
rotation-y : Rotates the video around the Y-Axis in degrees.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
rotation-z : Rotates the video around the Z-Axis in degrees.
flags: readable, writable
Float. Range: -3,402823e+38 - 3,402823e+38 Default: 0
编辑2：更新了代码，并提供以下解决方法：
class Thread(object):
def __init__(self):
thread = threading.Thread(target=self.get)
self.gltrnsfrm = Gst.ElementFactory.make("gltransformation","gltrnsfrm")
thread.start()
def get(self):
try:
global a,b,c
while True:
self.gltrnsfrm.set_property("rotation-z",a)
self.gltrnsfrm.set_property("rotation-x",b)
self.gltrnsfrm.set_property("rotation-y",c)
#time.sleep(0.01)
except KeyboardInterrupt:
pass
其余代码与帖子中之前所述相同（只是稍作改动即可使用线程）。但是，以下代码被省略：
#dynamic controller
cs = GstController.InterpolationControlSource()
cs.set_property('mode', GstController.InterpolationMode.LINEAR)
cb= Gstcontorller.DirectControlBinding.new(gltrnsfrm,"rotation-x",cs)
gltrnsfrm.add_control_binding(cb)
#modify the values
cs.set(0*Gst.SECOND,b) #use updated values of b
cs.set(1*Gst.SECOND,b)
答案 0 :(得分：0)
这里的问题是gltransformation属性是不可控制的。也就是说，它们在创建属性in the code时没有GST_PARAM_CONTROLLABLE标志。
您可以通过在上游提出补丁来增加gltransformation的可控性，也可以不依赖于可控的属性。