用于动态控制元素属性的Python Gstreamer

Question

我使用带有Python绑定的Gstreamer 1.0。以下是我尝试构建的考虑Opengl插件的管道：

gltestsrc -> gltransformation -> glimagesink

我正试图根据从外部硬件设备接收到的值动态修改元素"gltransformation"的属性。这是一个类似问题的链接，但它对我的用例没有太大帮助。下面是python脚本的剪辑：

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)

上面的例子只显示了对1元素属性的修改，然而，我还有其他属性要根据a,b & c的值进行修改。

执行上述脚本会出现以下错误：

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使其工作。有人参与这个问题吗？

编辑：根据休·费舍尔的建议，我试图追溯到文件的来源。以下是原始代码的一个片段：

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是可写和可读的。这里还有一个应用程序的链接，该应用程序从GUI获取输入并更改"gltransformation"的旋转-x/y/z。我不知道，为什么在我的情况下，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，并提供了解决问题的方法：

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

其余的代码与之前在文章中描述的相同(只是对使用线程进行了小的调整(。但是，以下代码被提交：

#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)

Answer 1

这里的问题是gltransformation属性是不可控的。即它们在代码中没有关于属性创建的CCD_ 2标志。

您可以通过在上游提出补丁来为gltransformation添加可控性，也可以不依赖可控属性。