Directshow in Python
Thomas Heller
theller at python.net
Fri Sep 19 02:43:17 EDT 2008
Sayanan Sivaraman schrieb:
> Hey all,
>
> I'm trying to use DirectShow to display videos [I'm kind of new to
> Python, from more of a C++ background on windows]. I found some
> sample code online, but I am having trouble with calling the I
>
> import ctypes
> from ctypes import *
> from comtypes import client
> from ctypes.wintypes import *
> import sys
> import time
>
>
> filename = sys.argv[1]
>
>
> qedit = client.GetModule('qedit.dll') # DexterLib
> quartz= client.GetModule("quartz.dll")
>
>
> CLSID_FilterGraph = '{e436ebb3-524f-11ce-9f53-0020af0ba770}'
> filter_graph =
> client.CreateObject(CLSID_FilterGraph,interface=qedit.IFilterGraph)
> filter_builder = filter_graph.QueryInterface(qedit.IGraphBuilder)
> filter_builder.RenderFile(filename, None)
>
> media_control = filter_graph.QueryInterface(quartz.IMediaControl)
> media_control.Run()
>
> try:
> # Look at IMediaEvent interface for EOS notification
> while True:
> time.sleep(1)
> except KeyboardInterrupt:
> pass
>
> # Need these because finalisers don't have enough context to clean up
> after
> # themselves when script exits.
> del media_control
> del filter_builder
> del filter_graph
>
> This code works fine. What I would like to know, is how do I declare
> filename in the Python program to be of type LPCWSTR, so that I don't
> need to parse the command line in order to call the function
> "RenderFile()"?
If I understand your question correctly (I'm no sure): comtypes converts
Python strings or unicode strings to the required LPCWSTR type itself.
So, you can call
filter_builder.RenderFile("c:\\windows\\clock.avi", None)
or
filter_builder.RenderFile(u"c:\\windows\\clock.avi", None)
If you pass a string, comtypes converts it to unicode using the "mbcs"
codec; this can be changed by setting ctypes.conversion_mode.
Thomas
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