Can someone give me some hints on using http progressive download in non http applications. I need to stream some video frames to a client application and display them. I need to develop the server side application and the client side application. I presume that the server side isn't too hard( I just receive a request and start transferring ). The client side is the problem for me. How can I approach this problem with regards to:
caching ( need some sort of caching in file )
indexing( the user must be able to salt to a specific time )
clean up( when to discard the file )
Shortly, I need an application in C++ that replicates the behavior of flash player.
Related
I am writing a server and client code where i want to identify on server side official client software sending data.
The protocol is text based, so anyone can write it's own client - and i want to keep it, but want to group the devices by "Official" / "Non Official" based on the 'fingerprint' of my official client application.
Question:
How can i filter out my clients from other clones sending?
I am thinking to send encrypted message from my client to SERVER using the same key, so once decoded if it's valid, then i know its my app code sending - but before i go this way, any other better ideas ?
I have developed a umdf2 driver and in some point it needs to communicate to a remote server to fetch some data. I am wondering is there any easy way (e.g. library) to do the http requests (GET, POST) in Windows user mode? I have never used winsock2 and I am not sure how easy/possible it's to use it?
Currently, I am using a kind of Pipe to hand this job to another app that resides upper level and uses Windows SDK to do this smoothly.
Any advice is greatly appreciated.
WinHTTP: https://learn.microsoft.com/en-us/windows/win32/winhttp/winhttp-start-page
filler filler filler
I am working on a face recognition project using Flask as my web server running on a Ubuntu 14.04 Machine. I am using OpenCV 2.4.9 as my image processing software which is written using Python2.7. I would like to be able to access a clients webcam through their browser to capture a image or frame from the webcam stream and send it back to the server to be processed. Is there an easy way using python to obtain access to the clients webcam or is it possible to use JavaScript in conjunction with my current code.
I'll assume that you are more interested in architectural decisions for you application that specific implementation details. You will need to use client side and server side for this application.
Client side is html page with javascript that will capture images from web cam. There are many resources on internet about this topic. This article explains how it works with some examples. I would recommend to use some javascript library like this one
The next thing is to decide how client application and server side transfers image data. In case you would like to stream webcam video to server, do some computation and stream data back to client application, WebSockets are your friend. This tutorial describes how to set up flask application for websockets.
Much easier approach is to POST image data to the server, do some computation and respond to client. Downside of this approach is that it's not suitable for continuous video processing. But you can use it for single video frame processing. Otherwise you would flooded your server with requests.
The last thing to decide is how much processing is done to images on server side. If you would do some extensive computation that takes long time, I would recommend celery for background tasks. HOWEVER this would change architecture considerably.
For a proof of concept, I would recommend following. Take single image with webcam, post it to server, do quick computation on image and respond with what you've had computed.
Good luck.
I have been trying to solve this for 2 weeks and I have not been able to reach a solution.
Here is what I am trying to do:
I need a web application in which users can upload a video; the video is going to be transformed using opencv's python API. Since I have Python's API for opencv I decided to create the webapp using Django. Everything is fine to that point.
The problem is that the video transformation is a very long process so I was trying to implement some real time capabilities in order to show the user the video as it is transformed, in other words, I transform a frame and show it to the user inmediatly. I am trying to do this with CoffeScript and io sockets following some examples; however I havent been successful.
My question is; what would be the right approach to add real time capabilities to a Django application ?
I'd recommend using a non-django service to handle the websockets. Setting up websockets properly is tricky on both the client and server side. Look at pusher.com for a free/cheap solution that will just work and save you a whole lot of hassle.
The initial request to start rendering should kick off the long-lived process, and return with an ID which is used to listen to the websocket for updates.
Once you have your websockets set up, you can send messages to the client about each finished frame. Personally I wouldn't try to push the whole frame down the websocket, but rather just send a message saying the frame is done with a URL to get the frame. Then normal HTTP with its caching and browser niceties moves the big data.
You're definitely not choosing the easy path. The easy path is to have your long-lived render task update the render state in the database, and have the client poll that. Extra server load, but a lot simpler.
Django itself really is focused on doing one kind of web interface, which is following the HTTP Request/Response pattern. To maintain a persistent connection with clients, which socket.io really makes dead simple, you need to diverge a bit from a normal Django installation.
This article discusses the issue of doing real-time with Django, with the help of Orbited and Twisted. It's rather old, and it relies on Comet, which is not the preferred way of doing real-time these days.
You might benefit a lot by going for Socket.io on the client, and something like Tornado (wiki) + Tornado client for Socket.io. But, if you really want to stick with Django for the web development (which Tornado also provide), you would need to make the two work together internally, each handling their particular use case.
Finally, this other article discusses how to make Django work with gevent (an coroutine-based networking library for Python) and Socket.io, which might well be your best option otherwise.
Don't hesitate to post questions/comments as they pop up!
So we have some server with some address port and ip. we are developing that server so we can implement on it what ever we need for help. What are standard/best practices for data transfer speed management between C++ windows client app and server (C++)?
My main point is in how to get how much data can be uploaded/downloaded from/to client via his low speed network to my relatively super fast server. (I need it for set up of his live stream Audio/Video bit rate)
My try on explaining number 3.
We do not care how fast is our server. It is always faster than needed. We care about client tyring to stream out to our server his media. he streams encoded (via ffmpeg) live video data to our server. But he has say ADSL with 500kb/s of outgoing traffic. Also he uses some ICQ or what so ever so he has less than 500 kb/s per second. And he wants to stream live video! So we need to set up our ffmpeg to encode video with respect to the bit rate user can provide. We develop server side and client side. We need a way of finding out how much user can upload per second currently (so value can change dynamically over time)
Check this CodeProject Article
it's dot-net but you can try figure out the technique from there.
I found what I wanted. "thrulay, network capacity tester" A C++ code library for Available bandwidth tracking in real time on clients. And there is "Spruce" and it is also oss. It is made using some of linux code but I use Boost library so it will be easy to rewrite.
Offtop: I want to report that there is some group of people on SO down voting on all questions on this topic - I do not know why they are so angry but they deffenetly exist.