Why can't webrtc find the capturer it suggested? - c++

Question

I'm creating a webrtc-based voip app for windows in C++. I'm trying to initialize a peerconnection. I'm stuck at the part to fetch a camera. I'm using the following code to find a camera to start streaming media from (copied from the peerconnection client example):
rtc::scoped_ptr<cricket::DeviceManagerInterface> dev_manager(cricket::DeviceManagerFactory::Create());
if (!dev_manager->Init()) {
LOG(LS_ERROR) << "Can't create device manager";
return NULL;
}
std::vector<cricket::Device> devs;
if (!dev_manager->GetVideoCaptureDevices(&devs)) {
LOG(LS_ERROR) << "Can't enumerate video devices";
return NULL;
}
std::vector<cricket::Device>::iterator dev_it = devs.begin();
cricket::VideoCapturer* capturer = NULL;
for (; dev_it != devs.end(); ++dev_it) {
capturer = dev_manager->CreateVideoCapturer(*dev_it);
if (capturer != NULL)
break;
}
capturer is empty after this procedure. I stepped through the code to see what was wrong. dev_manager is succesfully intialized, devs gets a single entry (my webcam) with a name:
"logitech HD webcam c270"
And an id:
"\\\\?\\usb#vid_046d&pid_0825&mi_00#7&2dbd1a82&1&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\\{bbefb6c7-2fc4-4139-bb8b-a58bba724083}"
But after the CreateVideoCapturer() call, capturer is still empty. I get a warning in the console saying:
Warning(webrtcvideocapturer.cc:175): Failed to find capturer for id: \\?\usb#vid_046d&pid_0825&mi_00#7&2dbd1a82&1&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\{bbefb6c7-2fc4-4139-bb8b-a58bba724083}
I checked if the id I get in devs and this one match and they do. The entire log for my app can be found in this pastebin. As you can see, right after trying to assign the camera as capturer and failing, the app crashes on an assert(capturer != NULL) call somewhere in videosource.cc.
The camera is not in use, nor is it defect. The peerconnection client example works perfectly and uses the same code. I think I'm missing some step in the initialization of webrtc, but I can't find which step.
edit with additional info
I'm debug stepping through the library now. In webrtcvideocapturer.cc around line 160 is the following code:
int num_cams = info->NumberOfDevices();
char vcm_id[256] = "";
bool found = false;
for (int index = 0; index < num_cams; ++index) {
char vcm_name[256];
int32 i = info->GetDeviceName(index, vcm_name, ARRAY_SIZE(vcm_name), vcm_id, ARRAY_SIZE(vcm_id));
if (i != -1) {
if (device.name == reinterpret_cast<char*>(vcm_name)) {
found = true;
break;
}
}
}
if (!found) {
LOG(LS_WARNING) << "Failed to find capturer for id: " << device.id;
factory_->DestroyDeviceInfo(info);
return false;
}
There are two problems with this part. First of all, if I step into info->NumberOfDevices() it shows me that that function's only content is the line return 0;. I tried hard-coding 1 there, to at least get into the for loop. Then when I step into the info->GetDeviceName() call it shows me that the content of that function is return -1;.
These two functions are meant to be implemented by a class that inherits from webrtc::VideoCaptureModule::DeviceInfo, so there is clearly something not initialized that does needs to be initialized. What do I still need to do before trying to get a camera?

Answer 1

What libraries did you link?
Because Google WebRTC source codes are changing rapidly, it is difficult to track down issues to the source level.
But I remember the almost same problem occurred when I accidentally linked external capture module library (video_capture_module_impl ??) or (I'm not sure) omitted internal impl (video_capture_module_internal_impl ??).