The problem background - there are two different windows applications that are trying to access webcam on the computer at the same time. Currently, only one application is able to access to it. I want to be able to allow both applications to simultaneously access the webcam. A common example of my problem is, skype and yahoo messenger trying to access the webcam on the computer at the same time.
I found a few softwares (manycam.com, http://www.splitcamera.com/) that allow this on windows. But I am not sure how they implemented it. I want to write the code myself to achieve this since my code needs to be integrated with other APIs.
I appreciate if anyone can shed light on how to write a device wrapper to achieve this.
The kernel camera driver registers several OS-defined callbacks. One of the callbacks is used for the output stream. Dedicated Windows applications have an interface to this stream - you'll need to do some reading on this subject, it's not something that can be covered in scope of SO. You need a component that will be layered in between the client applications and the camera driver. This component should intercept your camera driver output and duplicate it for the registered clients. This can be achieved either in kernel (filter driver) or in user mode (preferable). http://msdn.microsoft.com/en-us/library/windows/hardware/ff557573%28v=vs.85%29.aspx is a good place to start.
Note: this functionality might be already supported by your camera software (though I think the chances are very slim) and in this case you should dig into the corresponding documentation.
Related
I am writing a Go application for Mac and Windows, which will perform some action whenever there is a network change( Client move from Wi-fi 1 to Wi-fi 2 or to 3G to LAN). I am aware of a solution for Application running on mac in swift language but I am looking for a platform-agnostic solution here.
So far I have tried checking for an event on an interface but I am not sure if that is sufficient.
I expect that on a network change (moving from Wifi-1 to Wifi-2 or 3G or LAN) my Go app should be able to know to take some action.
I doubt there would be such a solution.
Every project which tries to provide some platform-agnostic solution to an inherently OS-tied problem inevitably hides the platform-specific details behind a common API.
Look at https://github.com/fsnotify/fsnotify for a good example.
So, I'd take that route and would have put up a package which would have two platform-specific "backends" which would be compiled conditionally using build tags.
To get notified about network-related events under Windows,
you should probably start here.
Unfortunately, this stuff is COM-oriented, but you could use https://github.com/go-ole/go-ole to help with that.
You might also ask a non-Go-specific question tagged winapi to ask about what would be the best way to hook into the kernel to get notified about the availability of the networks.
There is no platform agnostic solution that exists, however platforms like OSx,Linux,Windiws has ways to get network events with their platform specific limitations.
OSx: Raw socket SOCK_RAW of AF_ROUTE type can be used to detect any network events that occurs in user machine. there are various types of network event that can be detected.
This thread talk about an example on BSD for network event
Windows : Windows has its APIs given as part of iphlpapi library. APIs like NotifyAddrChange, NotifyRouteChange allows you to have almost all network events( apart from metric change etc.) this git repo has a working example NotifyAddrChange, which gives back and event whenever a interface goes down or comes up.
Linux : In Linux netlink sockets allows a user space application to receive network events using netlink sockets.
I have a camera that is ONVIF compatible.
If I want to zoom in/out, I presently have to send this URL to the camera:
http://192.168.2.88/cgi-bin/ptz_cgi?action=FocusAdd&steps=50&user=admin&pwd=admin
This is proprietary to my camera so I would like to do the same with ONVIF.
My question:
Is using onvif as simple as sending:
ONVIF://192.168.2.88:2010/some command ?
If so, what is the command :)
I am using Delphi XE2
Thank you.
No, it is not easy easy as a CGI protocol. The main differences are:
ONVIF is based on SOAP, while many proprietary protocols are based on REST or just parameters encoded in the URL
the ONVIF device model is more complicated, because it supports a wider set of use cases.
Thus, after you either generate the code from the WSDL files or get a library that implements the necessary functions, you have to do:
get the device services
verify that it has a PTZ service
verify that it has a Media service, either 1 or 2 (the latter is for profile T devices)
get the list of media profiles
select the media profile that has a PTZNode and that is actually the one you are looking for
select an adeguate coordinate space from the PTZ service capabilities
send the Move command with the correct parameters
This could seem overcomplex, but you need to remember that the ONVIF protocol needs to support devices with more that one input, such as multichannels encoders. These encoders may have a few fixed cameras and other cameras connected may have a PTZ controlled by the encoder. In practice, the list I just gave you lets you understand what the device you are controlling looks like.
I am working with Google Tango to extract data from the tablet and use it at the same time in another device. I am trying to record the data and use it with another laptop via live streaming.
I've looked at various topics about it and I found the Paraview topic. However the App records the data, save as ZIP file and send it via bluetooth(which is fine for me). I do not want to save the file as ZIP format and send it to another device. I want to record and use the data via live streaming(bluetooth or Wi-Fi).
Is that possible? How can I do it?
Paraview shared the source code so I think I can change it make it work for me. However I am not really used to programming.
Thank you very much for your help. I really appreciate it.
You might want to use sockets: setting a socket server on your computer and connecting to it via your tablet. It is a way to transfer information via what is called, for example, a TCP protocol.
However, there might be a more efficient way to do what you want to achieve with USB debugging. I did not got able to make USB debugging work yet on the tablet and computer I worked with.
You could use TangoAnywhere, I developed it so you can broadcast Google Tango position and orientation data to any device.
https://play.google.com/store/apps/details?id=de.grauonline.tangoanywhere
You connect using a TCP client on your PC/Mac (simple TCP client written Python or something) to port 8080 of your Tango device and will get the position data in realtime.
I recommend the Tango ROS Streamer app which enables you to choose which data (position, point cloud, RGB image) to stream or not.
You will need ROS to retrieve the data. On Linux ROS is easy to install, otherwise use a docker image of ROS.
Caution: the theorical WiFi bandwidth does not enable to stream all the RGB frames at full resolution without dropping some.
We're porting our USB device dll's to use the generic WinUsb.
However, WinUsb doesn't support multiple concurrent application accss to the same device (Same VID & PID).
I wanted to know if there is a way to implement this concurrent access using WinUsb?
I read about filter drivers & services.
1. I don't want to use a filter driver because, as I understand, this will have to pass WHQL, and I rather not go this path.
2. Regarding a windows service: How exactly should I implement it? should the service get all of the calls to WinUsb, and if a different application tries to access the same device, it will close the connection to the first application, open a new connection, and back again?
Is the service the right correct solution in this case? Is there another way to implement the solution other that what I wrote?
Thanks.
A filter driver does not need to pass WHQL. You only need to sign the catalog file, needed by the driver package. This only needs a code signing certigficate from verising/... . This should be a good starting place to get to know this.
Nevertheless, a kernel driver can be hard to develop. So maybe a COM server would be a better approach. You implement this sharing from a service, by allowing COM-clients to create objects from your service and then implement some kind of sharing/mutual exclusion in your COM-server.
A COM-exe servers can be written relativly fast.
I am currently working on a project that embeds a flash game, that uses Smartfoxserver for the flash communication. That communication is mostly just synchronizing the cursor and object movements between the two players.
Since I am not a flash guy, but a ruby programmer, I got curious: What kind of communication options does flash offer for this kind of time sensitive data exchange? I was thinking of writing a ruby-eventmachine based communication server to minimize the dependencies on external programs. Would that even be feasible?
Although I don't have a complete answer for you, because I'm not done myself, I have found myself in almost the exact same position as you.
My current approach is for my ruby server to essentially just be a socket server that handles all of the communication between clients, however I personally intend on keeping any of the logic outside of the server ( unless I run across a reason to change that idea).
If you haven't done any socket programming in ruby, I recommend the following as a jumping point. This is an IBM document on Ruby Socket programming and discusses an approach for asynchronous data:
Ruby Sockets - IBM
I think what it ultimately comes down to as well will be performance. I currently use a version of my ruby server in my daily work, but the data doesn't have to be updated in a time sensitive manner.
You can create a server in (almost?) any language that supports sockets and manage your clients with that.
From a flash perspective you could use ruby, but I don't know how fitted ruby would be for the task...I mean, you can make a PHP socket server but it would not handle much stress.
An alternative to SmartFoxServer could be open sourced Red5, written in Java.
If you want to know about flash built in capabilities in handling p2p:
Flash p2p: Everett Church
In Flash Player 10 adobe added Live media (RTMFP) support- Media was always sourced from the publishing peer. In Flash Player 10.1 beta they introduced groups and application-level multicast.
However, you would still need a server (Stratus) to handle introductions and manage active connections. ( Also, I regard it as geared towards flash video, Stratus does not support shared objects or scripting. So with Stratus, your applications will be clients communicating directly with each other.)
Edit:
After re-reading your question and the answer provided by Beanish, I think the first time I got your question wrong. So I just re-wrote my answer...