I am new to CRC8 calculation. But I want to perform CRC8 calculation with initial 0xFF. I have no idea how to use this initial 0xFF. Earlier, I was using this method as mentioned in "Error Detection With CRC" in http://computing.dcu.ie/~humphrys/Notes/Networks/data.polynomial.html.
My Msg Data is :8012h and Frame is 12D.
Please guide me.
It sounds like you don't quite know why you want an initial 0xff or what it's for. You should read Ross William's excellent CRC tutorial, which will give you a grounding in CRCs. (I provided five different links for the same article, in case the stackoverflow police come around complaining about stale links in answers. The last one is in Russian, just for kicks.)
You need to provide more information about what CRC-8 you are trying to generate. Are you trying to match some standard? What standard? Some interface? What interface?
Related
We have Google Natural AI integrated into our product for Sentiment Analysis (https://cloud.google.com/natural-language). One of the customers complained that when they write "BAD" then it shows a positive sentiment.
On further investigation, we found that when google Sentiment Analysis Natural Language API is called with input as BAD or Bad (pls see its in all caps or first letter caps ), it identifies text as an entity (a location or consumer good) & sends back the result as Positive while when we write "bad" in all small case, it sends negative.
Has anyone faced a similar problem? How did you solve it?
One obvious way looks like converting text into a small case but that may break some other use cases (maybe where entities do not get analyzed due to a small case text). Another way which we are building is to use our own dictionary of words with sentiments before calling google APIs but that doesn't answer the said problem, which may occur with any other text.
Inputs will help us. Thank you!
The NLP API uses an underlying model that is neural in nature. The knowledge comes from training on real world text. It is normal to get different results for different capitalizations as they can relate to different uses of the same trigram, e.g. Mike (person), mike (microphone, slang), MIKE (military alphabet entry).
The second key aspect is that the model is tuned and meant to be used on larger pieces of text and not on single words, hence good results can not be expected in this case.
I'm creating a simple editor in Mac OS X and I've come to the point where my editor needs to do some highlighting of code, for example, comments.
I am using Regex to find all comments, which I initially thought, was slow. Turns out, it does rather amazing job. For example, for 387 comments, regex needs "only" 0.008404 s to find them and returns array of NSRanges.
But here comes disaster. When I try to set different color to my text with method setTextColor:range: it completes very slow. It needs additional 9.872964 s (for those 387 comments I mentioned before) and it gets worse really fast when number of comments is increased.
So... Is there any way to do this faster? With NSAttributedStrings, perhaps?
I'm really sorry guys, but stackoverflow gave me suggestion on similar question (which I didn't found when I was searching).
It turns out you simply have to tell NSTextViews TextStorage that you will begin doing some editing. And when you finish, you commit those changes. Code looks like:
[textView.textStorage beginEditing];
// do some stuff here
[textview.textStorage endEditing];
Now I ran code with 456 comments, Regex needed 0.013887 s and coloring 0.215761 s, which is amazing drop!
Anyway, I hope someone will find that useful.
How do you make a list double spaced and continue the number? For example
This
Shouldn't
Be
Hard
If I add a line break then the numbering restarts from 1 again. Is there a way to make a whole numbered list double spaced or at least manually add some line breaks without resetting the count?
What is the point of wiki markup, why not just use HTML? It's at least as simple, if not more.
This works for me with Trac-1.0.1:
1. This [[BR]][[BR]]
1. Shouldn't [[BR]][[BR]]
1. Be [[BR]][[BR]]
1. Hard
I think it's because wiki markup is platform-, browser- and version-independent.
Complementing falkb's valuable answer on the first two of your three questions here are some words on Wiki markup:
I strongly disagree on your notion ('why not just use HTML?'), even more after being switched forcefully from Trac to a MS SharePoint business application. Me personal experience is:
Wiki markup is
simpler (and rather figurative/intuitive)
allows higher typing rate
easiler reviewable
faster to copy-n-paste and adapt
compared to equivalent HTML markup.
Most often used features like headings and list markup are a good example - very few extra characters in Wiki, just one additional char to add/remove for making a 2nd level a 3rd level heading. After I got a grip on Trac wiki markup syntax I started making plaintext notes outside of Trac's wiki editor in the same style too for clear text structur with minimal effort.
I have an int16_t[] buffer with PCM raw audio data and I want to apply some effects (like echo, reverb, gain...) into it.
I thought that SoX or similar can do the trick for me, but SoX only works with files and other similar libraries that supports adding sound effects seems to add the effects only when the sound is played. So my problem with this is that I want to apply the effect to the samples into my buffer without playing them.
I have never worked with audio, but reading about PCM data I have learned that I can apply gain multiplying each sample value, for example. But I'm looking for any library or relatively easy algorithms that I can use directly in my buffer to get the sound effects applied.
I'm sure there are a lot of solutions to my problem out there if you know what to look for, but it's my first time with audio "processing" and I'm lost, as you can see.
For everyone like me, interested in learning DSP related to audio processing with C++ I want to share my little research results and opinion, and perhaps save you some time :)
After trying several DSP libraries, finally I have found The Synthesis ToolKit in C++ (STK), an open-source library that offer easy and clear interfaces and easy to understand code that you can dive in to learn about various basic DSP algorithms.
So, I recommend to anyone who is starting out and have no previous experience to take a look at this library.
Your int16_t[] buffer contains a sequence of samples. They represent instantaneous amplitude levels. Think of them as the voltage to apply to the speaker at the corresponding instant in time. They are signed numbers with values in the range (-32767,32767]. A stream of constant zeros means silence. A stream of constant -32000 (for example) also means silence, but it will eventually burn your your speaker coil. The position in the array represents time, and the value of each sample represents voltage.
If you want to mix two sample streams together, for example to apply a chirp, you get yourself a sample stream with the chirp in it (record a bird or something). You then add the two sounds sample by sample.
You can do a super-cheesy reverb effect by taking your original sound buffer, lowering its volume (perhaps by dividing all the samples by a constant), and adding it back to your original stream, but shifting the samples by a tenth of a second's worth of array position.
Those are the basics of audio processing. Things get very sophisticated indeed. This field is known as "digital signal processing" and there are plenty of books on the subject.
You can do it either with hacking the audio buffer and trying to do some effects like gain and threshold with simple math operations or do it correct using proper DSP algorithms. If you wish to do it correct, I would recommend using the Speex Library. It's open source and and well tested. www (dot)speex (dot)org. The code should compile on MSVC or linux with minimal effort. This is the fastest way to get a good audio code working with proper DSP techniques. Your code would look like .. please read the AEC example.
st = speex_echo_state_init(NN, TAIL);
den = speex_preprocess_state_init(NN, sampleRate);
speex_echo_ctl(st, SPEEX_ECHO_SET_SAMPLING_RATE, &sampleRate);
speex_preprocess_ctl(den, SPEEX_PREPROCESS_SET_ECHO_STATE, st);
You need to setup the states, the code testecho includes these.
I am attempting to find documentation of the psd file format so I can read in a .psd and then save out the individual layers as files, along with do other modifications. Does anyone know of any document in on the .psd file format? (Just for reference, I will be writing this in C++)
If there are any code examples of loading a .psd file in C++ then I would appreciate them being linked.
(Please not turn this into a "just use XXX software". This is not homework, or anything related to that. I am doing this because I think it will be a fun project to work on. I will ask for posts to be down voted if this happens.)
There's also some Objective-C code on GitHub (should be easily understandable for anyone with a C++ background), also source of this gem, which appears to sum it up nicely:
At this point, I'd like to take a moment to speak to you about the Adobe PSD format.
PSD is not a good format. PSD is not even a bad format. Calling it such would be an
insult to other bad formats, such as PCX or JPEG. No, PSD is an abysmal format. Having
worked on this code for several weeks now, my hate for PSD has grown to a raging fire
that burns with the fierce passion of a million suns.
If there are two different ways of doing something, PSD will do both, in different
places. It will then make up three more ways no sane human would think of, and do those
too. PSD makes inconsistency an art form. Why, for instance, did it suddenly decide
that these particular chunks should be aligned to four bytes, and that this alignement
should not be included in the size? Other chunks in other places are either unaligned,
or aligned with the alignment included in the size. Here, though, it is not included.
Either one of these three behaviours would be fine. A sane format would pick one. PSD,
of course, uses all three, and more.
Trying to get data out of a PSD file is like trying to find something in the attic of
your eccentric old uncle who died in a freak freshwater shark attack on his 58th
birthday. That last detail may not be important for the purposes of the simile, but
at this point I am spending a lot of time imagining amusing fates for the people
responsible for this Rube Goldberg of a file format.
Earlier, I tried to get a hold of the latest specs for the PSD file format. To do this,
I had to apply to them for permission to apply to them to have them consider sending
me this sacred tome. This would have involved faxing them a copy of some document or
other, probably signed in blood. I can only imagine that they make this process so
difficult because they are intensely ashamed of having created this abomination. I
was naturally not gullible enough to go through with this procedure, but if I had done
so, I would have printed out every single page of the spec, and set them all on fire.
Were it within my power, I would gather every single copy of those specs, and launch
them on a spaceship directly into the sun.
PSD is not my favourite file format.
Just so you are warned. :)
This will not be a fun project, the .psd format is big. It incorporates every feature Adobe has put into Photoshop over many years.
I believe the specification can be had from Adobe, but they don't just hand it out to the public. You'll have to contact them and jump through some hoops first.
The PSD file format specification as written by Adobe is here;
http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/
Last update: June 2012. As far as I know this is the best available source about the PSD file format even there are few mistakes.
First I recommend starting by dividing PSD into blocks.
Enjoy!
MyPSD::CPSD class is a C++ class that can load images saved in Adobe's Photoshop native format.
http://www.codeproject.com/Articles/10398/Import-Adobe-Photoshop-psd-images
MolecularMatters psd_sdk seems like a good library to take inspiration form: https://github.com/MolecularMatters/psd_sdk
It allows to read layers from a .psd file and much more.