I am using file system type as "XFS" and i want to enable compression for XFS-file system. I surfed through the net but i couldnot found related data. If anyone aware of the compression for XFS-file system please let me know..
Thanks Guys,
XFS has no such facility as compression. See also Wikipedia which mentions it in the features box.
You would have to provide it on a higher level - or maybe at a lower one, if that exists (not that I am aware of, but one never knows)
Related
I want to make a sort of operating system, but with some very specific features.
The only thing i need it to do is show a video, place some text over it, accept user input and some basic file manipulation.
Something that looks like an OS'es loading screen would do.
i am, however, a complete noob to this part of programming and i have no idea where to look. Don't worry i do not need a complete explaination for every single step, but it would be nice to know in what direction i should go search.
Anyone got an idea where to start searching?
Thanks in advance ;)
Although you narrowed down your specification it's still complicated enough. Playing video involves file I/O, a file system, storage device access, buffering mechanism, memory allocation, memory management primitives, GPU access. Accepting user input requires keyboard and mouse handling which requires a working USB layer. Not to mention that you needed to make the video decoding library work with your own system, unless you want to implement that from scratch too. That might require you to have an ABI or a POSIX emulation layer. You might need to port at least one or two graphics libraries like SDL.
That's why "OS loading screen"s don't play videos :)
You might get away with using BIOS only for accessing all devices. But BIOS and VBE are usually slow and may not work well with your video playing scenario. BIOS is slowly getting pushed out of PC ecosystem in favor of UEFI too.
If you don't need a custom OS, you can trim a Linux kernel down to the parts you need to have. Even that's not a trivial thing to do though.
I want to read out and log my iMacs power consumption. Anybody has an idea how I can do that.
Swift, Shell or Ruby would be great!
Thanks a lot,
André
It sounds like you're talking about a non-laptop that doesn't use a battery, so there isn't nearly as much useful power usage information available as you might be able to get for a laptop that does use a battery.
But either way, if this were my problem I'd start writing a Swift app or a command line tool that incorporates the IOKit framework, which has a few header files with useful information, such as IOPowerSources.h and IOPSKeys.h.
More detail can be seen in the "Hardware Access Options" section of this Apple documentation.
Audio Messaging Interchange Specification. I am attempting to locate a copy of this rather old specification. Can anyone recommend where I might find this? All my searches have turned up endless references to glossaries but no actual specification.
Here is a start, but admitably it's not the complete specification. Perahps it's enough for your purposes though. There are actually two, AMIS-A (analog) and AMIS-D (digital).
I have developed a Windows application that captures video from an external device using DirectShow. The image resolution is 640x480 and the videos saved without compression have very huge sizes (approx. 27MB per second).
My goal is to reduce this size as much as possible, so I am looking for an encoder which will allow me to compress the video in real-time. It could be H.264, MPEG-2 or anything else. It must allow me to save the video to disk and it would be best if I also could stream it in real-time over network (Wi-Fi, so the size should be around 1MB per second, or less). The significant quality loss would be unacceptable.
I have found out that getting an appropriate DirectShow filter for this task is very difficult. It can be assumed that the client machine is reasonably modern (fast 2-core CPU) and can utilize CUDA/OpenCL. There are a few apps that allow to encode video using CUDA and offer good performance, however I have not found an appropriate DirectShow filter or an API which could be used to develop one. The NVIDIA nvcuvenc.dll seems to have private API so I am unable to use it directly. Any CPU-based encoders I have found are too slow for my requirements, but maybe I have missed some.
Could anybody recommend me a solution, i.e. an encoder (paid or free, that can be used in an closed-source app) that can achieve a good performance, regardless whether it is using CPU/CUDA/OpenCL or DirectCompute? Or maybe I should use some external hardware video encoder?
Best regards,
madbadger
Since you're using Directshow, by far the easiest thing to do would be to use WMV9 inside an ASF container. This is easier because it's available on almost all Windows machines (very few install time dependencies), decently fast (you should have no issues using it on a reasonably modern machine) and the quality is reasonable. But considering your limit is 8 mbit/sec (1 MB/sec), quality isn't an issue for you. 2 mbit/sec, VGA-resolution WMV9 should look quite good.
It's not nearly as good as a decent implementation of H264, but from an implementation standpoint, you're going to save yourself a lot of time by going this route.
See this:
http://msdn.microsoft.com/en-us/library/dd375008%28v=VS.85%29.aspx
Which filters have you tried?
If you're only dealing with 640x480, then any reasonable-quality commercial software-based encoder should be fine as long as you choose a realistic bitrate. Hardware acceleration using Cuda or OpenCL shouldn't be required. H264 takes a bit more horse-power and would require more CPU cores, but Mpeg2 or any of the h263-era codecs (xvid, wmv9, divx, etc) should have no problems even on a modest CPU. Streaming it over the network at the same time takes a little more effort, but should still be possible.
It's not DirectShow-based, but VLC Media Player can do all this. It's based on the FFMpeg open-source project. Some versions of it are LGPL-licensed, so the library could incorporated into your project without many restrictions.
If you just want a set of DirectShow filters that will handle all this for you, I've had good results with MainConcept's products before. They're at the expensive end of the spectrum though.
You dont specify what filters you've tried, or what 'significant' quality loss means, so about the best I suspect we can do is suggest some encoders to try to see if they meet your requirements.
Two good ones are the Theora and WebM video encoder filters (you can get them from a single installer at xiph.org). They're both high quality encoders which can be tweaked to balance performance vs quality. WebM can use multiple processors when encoding, which might help in your situation. Both are also used w/ HTML5 video, so that might be an extra plus for you.
Forget about WMV encoding for realtime streaming. WMV works well for realtime low quality streams, but it doesn't do high quality encoding in realtime.
I suggest that you take a look at MainConcept's SDK. They do a series of DirectShow filters for encoding H.264. I've implemented realtime streaming and muxing of streams encoded in H.264 using MainConcept's codec and DirectShow filters, and it's great.
Hope this helps
I am using Windows Media Encoder for real-time encoding, and it works well even in resolution 720x576. One such example of it's usage is in VideoPhill Recorder.
It is written in pure .NET with DirectShow.NET for capturing and windowsMedia.NET for encoding.
Using those two I am able to achieve real-time encoding with 24/7 stability.
And both libraries are free to use on Windows, so you won't have to pay any licenses except for OS.
ffdshow tryouts leverage ffmpeg's x264 stuff, which is said to be pretty fast (I think so anyway). Also libjpeg-turbo might help, or choosing some other codec made for high throughput like camstudio's or what not.
update: ffmpeg can take directshow input now: http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=3&t=27
Have you seen this yet?
http://www.streamcoders.com/products/rtpavsource.html
http://www.streamcoders.com/products/rtpavrender.html
If you can stay at or below 1280x1024, Micorsofts MPEG-2 encoder (included in Vista and up) is quite good.
I haven't gotten it to work for 1080p content at all though. I suspect the encoder just aborts on that. Shame.
Here is one option : http://www.codeproject.com/Articles/421869/H-264-CUDA-Encoder-DirectShow-Filter-in-Csharp
It uses about 10% of my cpu (p4 3ghz) to encode a SD video to h264 in graph edit.
See the CaptureDS C# sample that comes with AVBlocks. It shows how to build a video recorder with AVBlocks and DirectShow. DirectShow is used for video capture and AVBlocks is used for video encoding:
I've been involved in embedded operating systems of one flavor or another, and have generally had to work with whatever the legacy system had. Now I have the chance to start from scratch on a new embedded project.
The primary constraints on the system are:
It needs a web-based interface.
Inputs are required to be processed in real-time (so a true RTOS is needed).
The memory available is 32MB of RAM and FLASH.
The operating systems that the team has used previously are VxWorks, ThreadX, uCos, pSOS, and Windows CE.
Does anyone have a comparison or trade study regarding operating system choice?
Are there any other operating systems that we should consider? (We've had eCos and RT-Linux suggested).
Edit - Thanks for all the responses to date. A pity I can't flag all as "accepted".
I think it would be wise to evaluate carefully what you mean by "RTOS". I have worked for years at a large company that builds high-performance embedded systems, and they refer to them as "real-time", although that's not what they really are. They are low-latency and have deterministic schedulers, and 9 times out of 10, that's what people are really after when they say RTOS.
True real-time requires hardware support and is likely not what you really mean. If all you want is low latency and deterministic scheduling (again, I think this is what people mean 90% of the time when they say "real-time"), then any Linux distribution would work just fine for you. You could probably even get by with Windows (I'm not sure how you control the Windows scheduler though...).
Again, just be careful what you mean by "Real-time".
It all depends on how much time was allocated for your team has to learn a "new" RTOS.
Are there any reasons you don't want to use something that people already have experience with?
I have plenty of experience with vxWorks and I like it, but disregard my opinion as I work for WindRiver.
uC/OS II has the advantage of being fully documented (as in the source code is actually explained) in Labrosse's Book. Don't know about Web Support though.
I know pSos is no longer available.
You can also take a look at this list of RTOSes
I worked with QNX many years ago, and have nothing but great things to say about it. Even back then, QNX 4 (which is positively chunky compared to the Neutrino microkernel) was perfectly suited for low memory situations (though 32MB is oodles compared to the 1-2MB that we had to play with), and while I didn't explicitly play with any web-based stuff, I know Apache was available.
I purchased some development hardware from netburner
It has been very easy to work with and very well documented. It is an RTOS running uCLinux. The company is great to work with.
It might be a wise decision to select an OS that your team is experienced with. However I would like to promote two good open source options:
eCos (has you mentioned)
RTEMS
Both have a lot of features and drivers for a wide variety of architectures. You haven't mentioned what architecture you will be using. They provide POSIX layers which is nice if you want to stay as portable as possible.
Also the license for both eCos and RTEMS is GPL but with an exception so that the executable that is produced by linking against the kernel is not covered by GPL.
The communities are very active and there are companies which provide commercial support and development.
We've been very happy with the Keil RTX system....light and fast and meets all of our tight real time constraints. It also has some nice debugging features built in to monitor stack overflow, etc.
I have been pretty happy with Windows CE, although it is 'heavier'.
Posting to agree with Ben Collins -- your really need to determine if you have a soft real-time requirement (primarily for human interaction) or hard real-time requirement (for interfacing with timing-sensitive devices).
Soft can also mean that you can tolerate some hiccups every once in a while.
What is the reliability requirements? My experience with more general-purpose operating systems like Linux in embedded is that they tend to experience random hiccups due to their smart average-case optimizations that try to avoid starvation and similar for individual tasks.
VxWorks is good:
good documentation;
friendly developing tool;
low latency;
deterministic scheduling.
However, I doubt that WindRiver would convert their major attention to Linux and WindRiver Linux would break into the market of WindRiver VxWorks.
Less market, less requirement of engineers.
Here is the latest study. The last one was done more than 8 years ago so this is most relevant. The tables can be used to add additional RTOS choices. You'll note that this comparison is focused on lighter machines but is equally applicable to heavier machines provided virtual memory is not required.
http://www.embedded.com/design/operating-systems/4425751/Comparing-microcontroller-real-time-operating-systems