directshow capture filter chain (python)

dshow.py

#!/usr/bin/env python
# -*- encoding: utf-8 -*-

from comtypes import client, GUID
import interfaces as dsifs
from uuids import ids, rids

qedit = client.GetModule("qedit.dll")
quartz = client.GetModule("quartz.dll")
MFVideoARMode_PreservePicture = 0x1

# Helper functions.
def get_name(byte_array):
    name = "".join(map(chr, byte_array))
    try:
        name = name[:name.index('\x00')]
    except ValueError:
        pass
    return name

def get_pin(afilter, pin_name):
    pin_enum = afilter.EnumPins()
    while True:
        cur_pin, fetched = pin_enum.Next(1)
        if fetched:
            pin_info = cur_pin.QueryPinInfo()
            cur_pin_name = get_name(pin_info.achName)
            if pin_name in cur_pin_name:
                return cur_pin
        else:
            cur_pin.Release()
            break
    print("Pin '%s' not found!" % pin_name)
    return None

def build_graph():
    graph = client.CreateObject(ids.CLSID_FilterGraph,
    interface=qedit.IFilterGraph)
    # Provided with a graph, create a builder
    builder = graph.QueryInterface(qedit.IGraphBuilder)
    capture = client.CreateObject(ids.CLSID_CaptureGraphBuilder2,
        interface=dsifs.ICaptureGraphBuilder2)

    # Filter chain xbar -> tuner -> a/v decoders -> a/v renderers.

    ##
    # Crossbar
    # Fetch the first one and set it up to Composite input.
    dev_enum_xbar = client.CreateObject(ids.CLSID_SystemDeviceEnum,
        interface=dsifs.ICreateDevEnum)
    xbar_enum = dev_enum_xbar.CreateClassEnumerator(
        GUID(ids.CLSID_VideoCrossbarCategory),
        dwFlags = 0)
    xbar_enum.Reset()
    xbar_moniker, success = xbar_enum.RemoteNext(1)
    if not success:
        raise IndexError("Couldn't find crossbar device.")
    xbar_bind = xbar_moniker.RemoteBindToObject(None, None,
        dsifs.IBaseFilter._iid_)
    xbar_filter = xbar_bind.QueryInterface(dsifs.IBaseFilter)

    # Setup
    xbar = xbar_filter.QueryInterface(dsifs.IAMCrossbar)
    outputs_count, inputs_count = xbar.get_PinCounts()
    for i in range(0, inputs_count):
        related_pin_idx, pin_type = xbar.get_CrossbarPinInfo(True, i)
        if pin_type == dsifs.PhysConn_Video_Composite:
            input_pin_index = i
            related_input_pin_idx = related_pin_idx
            break
    for i in range(0, outputs_count):
        related_pin_idx, pin_type = xbar.get_CrossbarPinInfo(False, i)
        if pin_type == dsifs.PhysConn_Video_VideoDecoder:
            output_pin_index = i
            related_output_pin_idx = related_pin_idx
            break
    # Route video pins
    if xbar.CanRoute(output_pin_index, input_pin_index) == 0:
        if xbar.Route(output_pin_index, input_pin_index) == 0:
            routed_to = xbar.get_IsRoutedTo(output_pin_index)
            if routed_to != input_pin_index:
                raise Exception("Couldn't route crossbar pins!.")
    # Route related (audio) pins
    if xbar.CanRoute(related_output_pin_idx, related_input_pin_idx) == 0:
        if xbar.Route(related_output_pin_idx, related_input_pin_idx) == 0:
            routed_to = xbar.get_IsRoutedTo(related_output_pin_idx)
            if routed_to != related_input_pin_idx:
                raise Exception("Couldn't route related crossbar pins!.")
    graph.AddFilter(xbar_filter, "Crossbar")

    ##
    # Capture (TV Tuner) device
    # Fetch the first one and set it up to NTSC.

    dev_enum_cap = client.CreateObject(ids.CLSID_SystemDeviceEnum,
        interface=dsifs.ICreateDevEnum)
    cap_enum = dev_enum_cap.CreateClassEnumerator(
        GUID(ids.CLSID_VideoInputDeviceCategory),
        dwFlags = 0)
    cap_enum.Reset()
    cap_moniker, success = cap_enum.RemoteNext(1)
    if not success:
        raise IndexError("Couldn't find capture device!.")
    cap_bind = cap_moniker.RemoteBindToObject(None, None,
        dsifs.IBaseFilter._iid_)
    cap_filter = cap_bind.QueryInterface(interface=dsifs.IBaseFilter)
    cap = cap_filter.QueryInterface(interface=dsifs.IAMAnalogVideoDecoder)
    cap.put_TVFormat(dsifs.AnalogVideo_NTSC_M)
    graph.AddFilter(cap_filter, "Video Capture")

    ##
    # Connect crossbar to capture.
    graph.ConnectDirect(get_pin(xbar_filter, "0: Video Decoder Out"),
        get_pin(cap_filter, "Analog Video In"), None)
    graph.ConnectDirect(get_pin(xbar_filter, "1: Audio Decoder Out"),
        get_pin(cap_filter, "Analog Audio In"), None)

    ##
    # ffdshow filters
    # video
    ffds_vidraw = client.CreateObject(ids.CLSID_FFDshowRawVideoFilter,
        interface=dsifs.IBaseFilter)
    graph.AddFilter(ffds_vidraw, "ffdshow raw video filter")
    # audio
    ffds_auddec = client.CreateObject(ids.CLSID_FFDshowAudioDecoder,
        interface=dsifs.IBaseFilter)
    graph.AddFilter(ffds_auddec, "ffdshow Audio Decoder")

    # link to capture filters.
    graph.ConnectDirect(get_pin(cap_filter, "Capture"),
        get_pin(ffds_vidraw, "In"), None)
    graph.ConnectDirect(get_pin(cap_filter, "Audio Out"),
        get_pin(ffds_auddec, "In"), None)

    ##
    # Renderers.
    # audio
    dsound_renderer = client.CreateObject(ids.CLSID_DSoundRender,
        interface=dsifs.IBaseFilter)
    graph.AddFilter(dsound_renderer, "Default DirectSound Device")
    # video
    enhanced_video = client.CreateObject(ids.CLSID_EnhancedVideoRenderer,
        interface=dsifs.IBaseFilter)
    graph.AddFilter(enhanced_video, "Enhanced Video Renderer")

    # link to ffdshow filters.
    graph.ConnectDirect(get_pin(ffds_vidraw, "Out"),
        get_pin(enhanced_video, "EVR Input0"), None)
    graph.ConnectDirect(get_pin(ffds_auddec, "Out"),
        get_pin(dsound_renderer, "Audio Input pin (rendered)"), None)

    # All done, return the EVR Video Display Control and Graph Media Control
    evr_service = enhanced_video.QueryInterface(dsifs.IMFGetService)
    vdc_service = evr_service.GetService(GUID(ids.MR_VIDEO_RENDER_SERVICE),
        dsifs.IMFVideoDisplayControl._iid_)
    evr_videocontrol = vdc_service.QueryInterface(dsifs.IMFVideoDisplayControl)
    media_control = graph.QueryInterface(quartz.IMediaControl)
    return (media_control, evr_videocontrol)

if __name__ == "__main__":
    gr = client.CreateObject(ids.CLSID_FilterGraph,
        interface=qedit.IFilterGraph)
    print(build_graph(gr))