Re: [python-win32] Using DirectShow API to access webcam
Joe wrote: thanks for your helpful answer and the explanations. Following up on your comment on http://videocapture.sourceforge.net/ I found that there is jaraco.video, which seems to be "a port of the VideoCapture module in pure Python using ctypes and comtypes." (https://github.com/jaraco/jaraco.video) It is using a 'DirectShow.tlb' file, whatever that is, to get the definitions into comtypes. A TLB file is a "type library". It is a compiled version of the IDL for a set of COM interfaces. IDL is modified subset of C++ that is used to declare the functions within a COM interface, their parameters, and their types. It is intended to be a language-independent way to define the functions within an interface. Looks like you're on your way. -- Tim Roberts, t...@probo.com Providenza & Boekelheide, Inc. ___ python-win32 mailing list python-win32@python.org https://mail.python.org/mailman/listinfo/python-win32
Re: [python-win32] Using DirectShow API to access webcam
Hello Tim, thanks for your helpful answer and the explanations. Following up on your comment on http://videocapture.sourceforge.net/ I found that there is jaraco.video, which seems to be "a port of the VideoCapture module in pure Python using ctypes and comtypes." (https://github.com/jaraco/jaraco.video) It is using a 'DirectShow.tlb' file, whatever that is, to get the definitions into comtypes. https://github.com/jaraco/jaraco.video/blob/master/jaraco/video/api/__init__.py#L35 https://github.com/jaraco/jaraco.video/blob/master/jaraco/video/api/objects.py#L9 If your interested, I will post my progress on SO. Kind regards, Joe An "interface" in COM terms, described by an IID, is just a set of functions declarations. It defines the things you can do with an object, but it is not actually an object. A "CLSID", on the other hand, defines a COM object. The CLSID doesn't tell you what the object can do, it's just a way of creating an object. Once you have used a CLSID to create an object, you can ask it for an interface. So, you can't just create IID_IAMVideoProcAmp. You have to ask an existing object for its IAMVideoProcAmp interface. You would create your camera object, and then query the camera object for IAMVideoProcAmp. Creating a DirectShow graph is a multi-step process. You create a filter graph, you add your camera to the graph, you tell the graph to render the stream (which means it automatically fills in the other filters), and you control it. Here is some sample code that does this: https://gist.github.com/dust8/3890196 This is actually more complicated than it needs to be, because it's trying to handle TV devices with tuner and audio filters as well. You don't need that. Once you have a device from VideoInputDeviceCategory, you don't need the video decoder or the audio. You can just render the graph at that point. Alternatively, it looks like this package might be more applicable: http://videocapture.sourceforge.net/ ___ python-win32 mailing list python-win32@python.org https://mail.python.org/mailman/listinfo/python-win32 ___ python-win32 mailing list python-win32@python.org https://mail.python.org/mailman/listinfo/python-win32
Re: [python-win32] Using DirectShow API to access webcam
Joe wrote:
I have a question an hope you can help me. I am trying to control a
UVC webcam
using the DirectShow API, but could not get anything to work.
The question is already posted on StackOverflow:
https://stackoverflow.com/questions/51843523/accessing-webcam-via-directshow-using-com-with-python
I am not familiar with using CLSID, IID so playing with the few
examples I found
got my nowhere:
# IID_IAMVideoProcAmp is C6E13360-30AC-11d0-A18C-00A0C9118956
from win32com.client import Dispatch
from win32com.client.gencache import EnsureDispatch,GetClassForProgID,
GetClassForCLSID, GetModuleForProgID, GetModuleForCLSID
iid = '{c6e13360-30ac-11d0-a18c-00a0c9118956}'
print(GetClassForCLSID(iid))
print(GetModuleForProgID(iid))
print(GetModuleForCLSID(iid))
CLSID = IID('{c6e13360-30ac-11d0-a18c-00a0c9118956}')
print(CLSID)
print(Dispatch(CLSID))
pywintypes.com_error: (-2147220990, 'CONNECT_E_CANNOTCONNECT',
None, None)
Could someone of you point me in the right direction and maybe put
together a few lines to get me started?
I am not entirely convinced it is possible to control DirectShow from
Python, but I'll give you some general information.
An "interface" in COM terms, described by an IID, is just a set of
functions declarations. It defines the things you can do with an
object, but it is not actually an object. A "CLSID", on the other hand,
defines a COM object. The CLSID doesn't tell you what the object can
do, it's just a way of creating an object. Once you have used a CLSID
to create an object, you can ask it for an interface.
So, you can't just create IID_IAMVideoProcAmp. You have to ask an
existing object for its IAMVideoProcAmp interface. You would create
your camera object, and then query the camera object for IAMVideoProcAmp.
Creating a DirectShow graph is a multi-step process. You create a
filter graph, you add your camera to the graph, you tell the graph to
render the stream (which means it automatically fills in the other
filters), and you control it. Here is some sample code that does this:
https://gist.github.com/dust8/3890196
This is actually more complicated than it needs to be, because it's
trying to handle TV devices with tuner and audio filters as well. You
don't need that. Once you have a device from VideoInputDeviceCategory,
you don't need the video decoder or the audio. You can just render the
graph at that point.
Alternatively, it looks like this package might be more applicable:
http://videocapture.sourceforge.net/
--
Tim Roberts, t...@probo.com
Providenza & Boekelheide, Inc.
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Description: S/MIME Cryptographic Signature
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[python-win32] Using DirectShow API to access webcam
Hello,
I have a question an hope you can help me. I am trying to control a UVC
webcam
using the DirectShow API, but could not get anything to work.
The question is already posted on StackOverflow:
https://stackoverflow.com/questions/51843523/accessing-webcam-via-directshow-using-com-with-python
I am not familiar with using CLSID, IID so playing with the few examples
I found
got my nowhere:
# IID_IAMVideoProcAmp is C6E13360-30AC-11d0-A18C-00A0C9118956
from win32com.client import Dispatch
from win32com.client.gencache import EnsureDispatch,GetClassForProgID,
GetClassForCLSID, GetModuleForProgID, GetModuleForCLSID
iid = '{c6e13360-30ac-11d0-a18c-00a0c9118956}'
print(GetClassForCLSID(iid))
print(GetModuleForProgID(iid))
print(GetModuleForCLSID(iid))
CLSID = IID('{c6e13360-30ac-11d0-a18c-00a0c9118956}')
print(CLSID)
print(Dispatch(CLSID))
pywintypes.com_error: (-2147220990, 'CONNECT_E_CANNOTCONNECT', None,
None)
Could someone of you point me in the right direction and maybe put
together a few lines to get me started?
Kind regards,
Joe
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