I am able to use the aux clock API's from Kernel Image project, but when tried to use the same API's for example sysAuxClkRateSet( int ticksPerSecond ) in the RTP Project, i am getting undefined reference to the sysAuxClkRateSet error. I'm working on Vxworks 7.0. I added the API to the custom system call list and tried it, the compiler errors are getting resolved, but when the control hits that API, it is failing to work and the board is rebooting. I'm using TI Sitara a9, 4377 board. Any inputs on how to get it worked would really help. Thanks in advance !!
sysAuxClkRateSet is a Kernel Space API, and is not present in the user mode header files.
In order to use this functionality from an RTP you can either use a mechanism such as a msgQ, to send commands from an RTP to a kernel space task, or write a custom system call to expose this function.
For this particular use case, you would probably want to create a static system call, which means you can call sysAuxClkRateSet directly from the RTP. This would require modifications to, and rebuild of, the VxWorks libraries, so you will probably want to base your kernel on a VSB project rather than the default libraries - although if you are using VxWorks 7 you will already have a VSB.
sysAuxClkRateSet is kernel space API hence will not work in RTP.
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Using PortAudio, how can I access running applications' audio interface so that I can capture the audio they produce in real time? The goal would be then to send this audio as UDP packet to a server.
I've had a look at PortAudio's code samples but can't find anything similar.
Maybe PortAudio is not the right library for me?
I'm working mainly on Mac OS.
Core Audio does not have the sort of functionality you're looking for. Processes are sandboxed/isolated from one another.
You could probably achieve this using library injection, but there are a number of complications. OSX has added System Integrity Protection which disables injections. If you're willing to disable SIP (which is dangerous! Proceed at your own risk!) then you could try something like mach_inject and intercepting the target processes' calls to Core Audio. But you'd never be able to ship something like this, since asking users to disable SIP is not reasonable.
I need to extract audio from video and save it. FFmpeg has command for this purpose. I wonder if it is a right way to execute ffmpeg from my code and not to write code with their API functions.
The lack of this approach is that I use Qt Framework and need cross-platform application. Sometimes (especially in windows, because PATH variable doesn't set up automatically so call ffmpeg won't work) a user will need to indicate path to executable file to run in command line.
So both variants are possible to realize, but which is the best and correct one?
I don't really want to use their API because it is not so easy to understand and will take time to write my own code.
Thanks for any advice!
Using standalone ffmpeg seems to be preferred in your case. You will have to bundle ffmpeg and it's dependencies along with your application. However there is no need to set or use PATH or other environment variables to launch ffmpeg. You should do it by supplying full path to ffmpeg executable.
Using libav API is indeed rather tricky. And I would like to mention that in general (depending on codec) ffmpeg and libav should not be considered stable and you should spawn a separate process to protect main executable from potential crash in this case as well. So complexity of this approach is much higher compared to first one.
Disclaim: I never used Qt with ffmpeg together myself, but have much experience with Qt especially.
Qt tends to try having everything in their library, wrapping many other content for convenience. Most of the time (All those I tested), it is still possible quite easily to use the original library without troubles, but the Qt facilitate integration.
As an example: QOpenGLWidget is a wrapper for OpenGL with their widget system, adding signals and slots, etc. I made some test using normal OpenGL and it worked fine.
In another project, we(my team, not me particularly) used ffmpeg to display video on a QtWidget. It works with limited problems (due to other architectural requirements).
Considering your use case, and especially that you are using ffmpeg for background processing and not for displaying video, you may IMO go ahead with high probability of success.
So I need to simulate Isis2 in ns-3. (I am also to modify Isis2 slightly, wrapping it with some C/C++ code since I need at least a quasi real-time mission-critical behavior)
Since I am far from having any of that implemented it would interesting to know if this is a suitable way of conduct. I need to specifically monitor the performance of the consensus during sporadic wifi (ad hoc) behavior.
Would it make sense to virtualize a machine for each instance of Isis2 and then use the tap bridge( model and analyze the traffic in the ns-3 channel?
(I also am to log the events on each instance; composing the various data into a unified presentation)
You need to start by building an Isis2 application program, and this would have to be done using C/CLI or C++/CLI. C++/CLI will be easier because the match with the Isis2 type system is closer. But as I type these words, I'm trying to remember whether Mono actually supports C++/CLI. If there isn't a Mono compiler for C++/CLI, you might be forced to use C# or IronPython. Basically, you have to work with what the compiler will support.
You'll build this and the library on your mono platform and should test it out, which you can do on any Linux system. Once you have it working, that's the thing you'll experiment with on NS/3. Notice that if you work on Windows, you would be able to use C++/CLI (for sure) and then can just make a Windows VM for NS3. So this would mean working on Windows, but not needing to learn C#.
This is because Isis2 is a library for group communication, multicast, file replication and sharing, DHTs and so forth and to access any particular functionality you need an application program to "drive" it. I wouldn't expect performance issues if you follow the recommendations in the video tutorials and the user manual; even for real-time uses the system is probably both fast enough and steady enough in its behavior.
Then yes, I would take a virtual machine with the needed binaries for Mono (Mono is loaded from DLLs so they need to be available at the right virtual file system locations) and your Isis2 test program and run that within NS3. I haven't tried this but don't see any reason it wouldn't work.
Keep in mind that the default timer settings for timeout and retransmission are very slow and tuned for running on Amazon AWS, inside a data center. So once you have this working, but before simulating your wifi setup, you may want to experiment with tuning the system to be more responsive in that setting. I'm thinking that ISIS_DEFAULTTIMEOUT will probably be way too long for you, and the RTDELAY setting may also be too long for you. Amazon AWS is a peculiar environment and what makes Isis2 stable in AWS might not be ideal in a Wifi setting with very different goals... but all of those parameters can be tuned by just setting the desired values in the Environment, which can be done in bash on the line that launches your test program, or using the bash "Export" command.
i need to add some files to results returned by FindFirstFile and FindNextFile under windows. Is this possible by file system filter driver or what type of drivers?
Thank you
You can do this by File System Filter Driver. But you can do this by implementing a system wide API hook. I have not tried it before but you really don't need to take the pains of writing the drivers and making the system unstable in case of spoiling the driver stack.
System Wide API Hooking
API Hooking Revealed
As pointed out you can use a file system filter driver (legacy or mini-filter, based on fltmgr). However, I would strongly recommend against the system-wide API hooking. Simple reason: if you do it in usermode it's not really going to be system-wide and if you use an SSDT-hook or some hotpatching method you risk the system's stability. An alternative, albeit equally shady as system-wide hooking, would be entry-point stealing. In this case you use the device object of the volume (in which you're interested, just listen for the attach notifications or enumerate them at startup) to find the driver responsible for it and modify the major function entry points in the driver object (Ilho pointed you into the right direction already).
A file system filter driver is the supported method to do just that.
In the latest Windows 7 WDK the sample under 7600.16385.1\src\filesys\miniFilter\minispy provides a good starting point. Biggest problem with mini filters for a private person is to get assigned an altitude for the driver to load at. Because using just any altitude can well lead to BSODs - and in case of FSFDs you might even risk your data integrity (although the kernel steps in with the BSOD to prevent that). You only need to fake IRP_MN_QUERY_DIRECTORY - this is the minor control code you're looking for when you are handling the IRP_MJ_DIRECTORY_CONTROL major control code. All others you can pass through as long as you don't need to allow the file to be opened, read or written and such. How to do that can be seen in the 7600.16385.1\src\filesys\miniFilter\passThrough sample source.
My main goal is to create an advanced program for manipulating the packets that route within my network via the router. Let my program have total control over the router. Set the download/upload speeds to my inputs, apply the effect to certain devices within in my network. Block upload or download traffic. Set second delay for either the upload or download speed. Specify % of loss packets, and the list goes on.
The problem is that I don't know where to start. I know most languages at the very most basic level. I'd like to create this program in either C, C++ or C# but I don't know yet. What else do I need to know before creating this program? Winsock or something? Winpcap APIs?
This goal is my motivation to learn programming to the extreme, and I'm really looking forward to it.
Thanks in advance!
Hmmm I guess you would want to look at pcap(?):
pcap
Check out:
http://beej.us/guide/bgnet/html/multi/index.html
'Beej's Guide to Network Programming
Using Internet Sockets'
All you could possibly need to know about programming sockets for capture and manipulation.
If I were you I'd write it in C, I'm writing a similar project at the moment in C++ and it's hell but too late to stop and start again.
Hope that helps.
Bear in mind that you either need a router that you can re-program or you need to use your PC as a router to do this.
Either way you want to look into how IPTABLES are implemented.
I've never seen Desktop Windows used as a router only Windows Server, though it may still be possible. libpcap is for packet capture, but not interception as I understand it. Programs like Wireshark use it to monitor copies of packets, but not to modify them. If you want to attempt this, my impression has been that there is a lot more documentation and tools for doing something like this with NetFilter/IPTables on Linux. You can even install something like OpenWRT on a compatible router and get a small, cheap Linux router, though having Desktop Linux will probably help for development. The NetFilter QUEUE library can be used with some IPTables firewall rules to redirects specific (or all) packets to a regular user program. That program can then read the packet and modify it or even request it to be dropped.
http://www.netfilter.org/projects/libnetfilter_queue/
If you want to manipulate network traffic on a Windows machine (as you mentioned), you will need some extra software. This operating system wont give you the full control over itself, which is fine for some reasons.
I think what you want to do, should be done with either winpcap or win10pcap if you are using Win10. These packages contains a windows driver and the libpcap user space library.