I just want to know if its possible to write a program in c++ on Windows which can grab frames of video from a web cam by making use of a USB library like libusb.
I have looked at http://www.dreamincode.net/forums/topic/148707-introduction-to-using-libusb-10/ . They define a basic sequence of the steps one must follow while using libusb to work with usb devices. To summarize:
1) Find and connect to the USB device
2) Send and receive data
3) Release the USB device
libusb handles part 1) and 3). So, the question comes down to part 2). I wonder if it is possible/feasible to send commands to the camera and receive data via USB by adhering to some type of standard (UVC 1.5 for example). I'm thinking that not knowing some proprietary, device specific information might be a problem though.
If this is possible but super hard, I would appreciate any insights into what the biggest challenge would be.
The hardware I have in mind are low-end logitech USB cameras.
Also, I am fully aware that OpenCV, Video for Windows (VFW), DirectShow, and FFMPEG can do web-cam video capture. I am interested in this project as a learning experience.
Thanks in advance!
Since you're obviously a bit inexperienced, I'll give an answer in high-level terms.
To talk to someone, or something, you need to speak a common language, or have a translator. Now, there are many different USB devices, and they speak many different languages, but OpenCV can act as a translator for many of those. If you don't want to use that, you will need to find another translator, or possibly learn to speak the camera's native language.
The first option (another translator) is no option for you, because you don't want a translator.
The second option is something we can't help you with, because we don't know which camera you have.
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I am kind of a beginner in programming, learning it in school, so I really don't know much.
But I want to make a program for PC and maybe app for iPhone/Android that receives a video-stream from a camera and displays it, nothing more.
How do I do this in C++/C# in Visual Studio?
Camera -> WiFi -> PC/Phone
A good library for working with images/video in c++ is OpenCV. I would recommend taking a look at their examples.
http://docs.opencv.org/3.0.0/index.html
Check out the highgui module!
You should first check for cameras that come with a programming API so that it is easy to write programs to communicate with it.
If the camera drivers can make it communicate with standard chat apps like Sykpe, you should be able to use C++ and OpenCV to capture a stream from it. But you can choose the language and tools according to what you want to do with the video stream.
I'm currently building a c++ program (with Qt) to take picture from a camera device. This part is actualy done, now I need to control 8 flashs divided in two groups in an automatic way.
The flash I already use are from ELINCHROM http://www.elinchrom.com/ and this device seems to be perfect for what I need but I could not find anywhere a way to control it from a different application than the one elinchrom propose.
Do you know if what I intend to do is even possible? If a solution exist with another brand I will also take it.
Thank you in advance for any replies, and please excuse my english.
Should be possible; the driver guide states that the driver is really a USB serial port driver. That means you can probably reverse-engineer the protocol.
I want to capture all audio that is played to the user (all sounds together). Currently I'm working on Windows but it would be nice if the code was cross-platform (but not necessarily). Is it possible to do it with OpenAL? How? Code examples would be great.
Language: C++
The only way to do this I believe is to create a replacement audio device driver that receives all audio requests, and then forwards them to the original device driver. There are a number of existing applications that work in this way including Freecorder, MP3myMP3 Recorder, SoundTap and Wondershare to name but a few (Google "Streaming Audio Recorder").
As for cross-platform, I would say not a chance since it is OS driver model dependent.
Depending on what you have in your system, some (not all) sound cards offer a "Stereo Mix" feature, which can be used like any other recording device. This is basically exactly what you want, as it is literally a mix of all stereo sounds being played.
I'm not actually well versed in C++ or SDL_Mixer, but I'm asking this question anyway on behalf on the Doom community. Put simply, nobody writing Doom source ports can seem to figure out how to control normal sound volume and MIDI sound volume independently using SDL_Mixer on Windows Vista or 7. I'll let James Haley, author of Eternity Engine, put it in his own words:
Seems the concept of independent volume for native MIDI doesn't exist under Windows Vista or 7, as using MIDI volume sliders in any application that has them (including most games that use SDL_mixer) also affects the volume of digital sound output. This makes attempting to adjust the relative volume of music for comfort impossible.
Has anybody found any workarounds for this? I'm guessing it's unlikely given how Microsoft seems to have skimped throughout the OS on any way to control the volume of individual sound devices separately.
I've heard of various workarounds all involving a Timidity driver, but this requires the user go above and beyond simply installing the game on his system. The only port that I know of that definitively fixes this issue is ZDoom, but it uses the GPL-incompatible FModEx and is thus not a suitable solution.
If you want some code to look at, Chocolate Doom is perhaps the easiest Doom source port to grok and you can grab its source here.
Any suggestions on other open-source sound and music libraries would be welcome as well.
A solution would be to ship with a FluidSynth-enabled SDL_mixer. You would also need to ship a SoundFont2 file to go with it. Fortunately, there are free SF2's out there, and some are even optimized for Doom's MIDI files. Licenses shouldn't be a problem, since SoundFonts are assets, not code.
You then load the SF2 using Mix_SetSoundFonts().
You may want to look at different MIDI libraries outside of SDL.
http://wildmidi.sourceforge.net/
http://sourceforge.net/apps/trac/fluidsynth/
http://timidity.sourceforge.net
I am maintaining a similar game port (Descent 2), and I have come across the same problem. Afaik there is no solution for it when using SDL_mixer. A cure to avoid sound being muted when turning off midi music I have found is to retrieve a handle to a temporary midi device, set the midi volume to max and then close the temporary device again.
For the longest time, the only solution we found was to use something like PortMIDI. However, Quasar of Eternity Engine fame has come across a neat solution:
http://www.doomworld.com/vb/showthread.php?s=&postid=1124981#post1124981
He essentially puts SDL_Mixer into its own process and controls it with RPC. Very clever.
So one problem with the previous answer I gave was that sometimes the MIDI subprocess did not behave itself, and would break or stop working in strange ways. Eternity's specific implementation used IDL, and I personally re-implemented it using pipes, but the subprocess itself was a bug magnet.
Thankfully, another answer was figured out rather recently. You can simply bypass SDL_Mixer entirely and deal with Windows' native MIDI support directly, which turns out to not require a ton of code once you know what you're doing.
https://github.com/chocolate-doom/chocolate-doom/blob/master/src/i_winmusic.c
You can also implement this sort of idea with PortMIDI and get the benefit of being able to communicate with external MIDI devices as well.
https://github.com/odamex/odamex/blob/stable/client/sdl/i_musicsystem_portmidi.cpp
I want to develop code to transmit data from system to PIC through USB.
Can anybody give good link regarding data transmission through USB.
because i am new to this.
NOTE: Very simple is code is enough to me.
Thanks in Advance
The PIC16F877 does not have a USB peripheral built in. I assume that the product that you are building is a "USB Device" and that the "system" that you are referring to will provide the USB host functionality. If this is the case then you will have to add a USB interface chip to your hardware to provide async serial to USB connectivity. Suitable devices are made by TI (TUSB series) or FTDI. You then connect one of these to the PIC internal USART and pretend that you are transferring the data over a simple serial port. If you are using a pc then the connected device will appear as a standard COMn: port.
I totally agree with the FTDI route, however if you're not looking for a UART tunnel over USB then you have to get a bit more in-depth.
You'll have to write the USB routines yourself or find libraries/projects for your processor. What you will definitely have to have is a fast clock - 12MHz is necessary More is better because on small uC's like these you'll spend most of your time just handling the basics of USB - signaling and so forth. You'll also need a fair bit of memory because the USB code takes up around 1.5K I think. Then you need room afterwards for your own code.
I've seen the V-USB (http://www.obdev.at/products/vusb/index.html). It's for AVR not PIC, but it says it provides all of the USB functionality you'll need and even provides vendor and product IDs for you to use (non-commercial I believe). There's also a PIC project for USB that doesn't run on the same hardware as yours here: http://www.alanmacek.com/usb/
To make the driver you'll have to use libusb - here's a link for the win32 version: http://libusb-win32.sourceforge.net/
It's surprisingly more simple than I had expected, but I just looked at example code and not actually made anything. Good luck!
As your task will involve Windows Device Driver development, I do recommend to downlaod and install the WDK and look through the contained sample USB drivers.
This might get you some hints about the complexity of the topic. Device driver development is not the easiest thing to start with.
Maybe you can start with UART communication (RS232).
check http://www.beyondlogic.org/usbnutshell/pic16f876.gif will surely help u
also
ttp://www.beyondlogic.org/usbnutshell/usb7.htm , type h in front of 2nd link.