I am writing a binary reader that needs to read in a very specific set of binary written by an Android Tablet. I have run into several issues reading this binary, the first and foremost being that it does not resemble the data I wrote in the first place. I have read a little bit about endianness, words, and how they are made on different systems and I am curious as to if this could be the root of the problem.
Any information would be good at this point, but the specific thing I would like to know is: Considering the lines below, why is the binary not being read in as the same value as it is written out as? How can I fix this?
Say numPoints = 5000.
(OUT FUNCTION - Android-java)
out.writeInt(numPoints);
(IN FUNCTION - UE4-c++)
reader << numPoints;
numPoints now equals some really really large number that I can't explain.
I am using Windows 8.1 x64 and a Google-Project-Tango Tablet.
Your C++ code is probably reading numbers in little-endian. Java (at least DataOutputStream) writes binary numbers as big-endian.
It's probably simpler to fix this on the Java side since there's a built-in function for it:
out.writeInt(Integer.reverseBytes(numPoints));
You should also check whether UE4 guarantees that binary files are little-endian, or whether it's the machine's native endianness - otherwise there's a chance that you might want to port your game to a big-endian platform and run into problems later.
Related
I’m trying to build a sketch that shows me levels of audio coming into a system. I want to be able to do more than 2 channels so i know that i need more than the processing.sound library can provide currently and my searching has led me to javax.sound.sampled.*, however this is as far as my searching and playing has got me.
Does anyone know how to query the system for how many lines are coming in and to get the amplitude of audio on each line?
This is kind of a composite question.
For the number of lines, see Accessing Audio System Resources in the Java tutorials. There is sample code there for inspecting what lines are present. If some of the terms are confusing, most are defined in the tutorial immediately preceding this one.
To see what is on the line, check Capturing Audio.
To get levels, you will probably want to do some sort of rolling average (usually termed as root-mean-square). The "controls" (sometimes) provided at a higher level are kind of iffy for a variety of reasons.
In order to calculate those levels, though, you will have to convert the byte data to PCM. The example code in Using Files and Format Converters has example code that shows the point where the conversion would take place. In the first real example given, under the heading "Reading Sound Files" take note of the place where the comment sits that reads
// Here, do something useful with the audio data that's
// now in the audioBytes array...
I recall there are already StackOverflow questions that show the commands needed to convert bytes to PCM.
I'm making program for Active Noise Control(also use Adaptive instead of Active / use Cancellation instead of Control)
System is pretty simple.
get sound via mic
turn the sound into data, which I can read(Something like Integer array)
make antiphase of the sound.
turn the data into sound file
Follwing is my question
Can I read sound as Integer Array?
If I can use Integer Array, how can I make antiphase? Just multiply -1 to every data?
Any useful think about my project
Is there any recommended language rather than java?
I heard that stackoverflow have many top class programmers. So, I expect for critical answer :D
Answering your questions:
(1) When you read sound, a byte array is returned. The bytes can readily be decoded into integers, shorts, floats, whatever. Java supports many common formats, and probably has one that matches your microphone input and speaker output. For example, Java supports 16-bit encoding, stereo, 44100 fps, which is considered the standard for CD-quality. There are several questions already at StackOverflow that show the coding for the decoding and recoding back to bytes.
(2) Yes, just multiply by -1 to every element of your PCM array. When you add the negative to the correctly lined up counterpart, 0 will result.
(3 & 4) I don't know what the tolerances are for lag time! I think if you simply take the input, decode, multiply by -1, recode, and output, it might be possible to get a very small amount of processing time. I don't know what Java is capable of here, but I bet it will be on the scale of a dozen millis, give or take. How much is enough for cancellation? How far does the sound travel from mike to speaker location? How much time does that allow? (Or am I missing something about how this works? I haven't done this sort of thing before.)
Java is pretty darn fast, and you will be relatively close to the native code level with the reading and writing and simple numeric conversions. The core code (for testing) could probably be written in an afternoon, using the following tutorial examples as a template: Reading/Writing sound files, see code snippets. I'd pay particular attention to the spot where the comment reads "Here do something useful with the audio data that is in the bytes array..." At this point,
you would put the code to convert the bytes to DSP, multiply by -1, then convert back to bytes.
If Java doesn't prove fast enough, I assume the next thing to try would be some flavor of C.
I was storing some files based on a checksum but I found a flaw that 2 checksums can be identical sometimes.
I always try looking for API instead of reinventing the wheel, but I can't find anything.
I know theres the JSR 268 and JackRabbit as a standard for content storage but my app is light-years of using such thing.
So, are there approaches for single Instance File Storage with Java or should I just keep searching for new algorithms for my checksum?
EDIT:
When numcheck is not working: 2 files are exactly the same, just in different file system locations. However when sent from the client is impossible on server side to know the path they were before, so it is the same file twice, same checksum.
If you wanna retrieve either one, how you check that?
Wanted to know if there was an standard approach, API, or an algorithm that could help me spot the difference
No matter how strong a hashing algorithm is, there is always a chance of a collision. A hashing algorithm generates a finite number of hashes from an infinite number of inputs.
The only way to ensure that two files are not identical is to compare them bit by bit. Hashing them is easier and faster, but carries with it the risk of collision.
I've been researching this off-and-on for a few months.
I'm looking for a library or working example code to detect the frequency in sound card audio input, or detect presence of a given set of frequencies. I'm leaning towards Java, but the real requirement is that it should be something higher-level/simpler than C, and preferably cross-platform. Linux will be the target platform but I want to leave options open for Mac or possibly even Windows. Python would be acceptable too, and if anyone knows of a language that would make this easier/has better pre-written libraries, I'd be willing to consider it.
Essentially I have a defined set of frequency pairs that will appear in the soundcard audio input and I need to be able to detect this pair and then... do something, such as for example record the following audio up to a maximum duration, and then perform some action. A potential run could feature say 5-10 pairs, defined at runtime, can't be compiled in: something like frequency 1 for ~ 1 second, a maximum delay of ~1 second, frequency 2 for ~1 second.
I found suggestions of either doing an FFT or Goertzel algorithm, but was unable to find any more than the simplest example code that seemed to give no useful results. I also found some limitations with Java audio and not being able to sample at a high enough rate to get the resolution I need.
Any suggestions for libraries to use or maybe working code? I'll admit that I'm not the most mathematically inclined, so I've been lost in some of the more technical descriptions of how the algorithms actually work.
If you are aiming at detecting frequency pairs then your job is very similar to a DTMF detector.
Try searching for DTMF in places like sourgeforge, you'll find detectors in many programming languages. The frequency pairs placing along the spectrum seems to be even more stringent than your specs so you should be fine adapting a DTMF detector to your input.
Check out SNDPeek, its a cross-platform C++ application that extracts all kinds of information from live audio; https://github.com/RobQuistNL/sndpeek
I was wondering if anyone had experience retrieving data with the 3270 protocol. My understanding so far is:
Connection
I need to connect to an SNA server using telnet, issue a command and then some data will be returned. I'm not sure how this connection is made since I've read that a standard telnet connection won't work. I've also read that IBM have a library to help but not got as far as finding out any more about it.
Parsing
I had assumed that the data being returned would be a string of 1920 characters since the 3278 screen was 80x24 chars. I would simply need to parse these chars into the appropriate fields. The more I read about the 3270 protcol the less this seems to be the case - I read in the documentation provided with a trial of the Jagacy 3270 Java library that attributes were marked in the protocol with the char 'A' before the attribute and my understanding is that there are more chars denoting other factors such as whether fields are editable.
I'm reasonably sure my thinking has been too simplistic. Take an example like a screen containing a list of items - pressing a special key on one of the 24 visible rows drills down into more detailed information regarding that row.
Also it's been suggested to me that print commands can be issued. This has some positive implications - if the format of the string returned is not 1920 since it contains these characters such as 'A' denoting how users interact with the terminal, printing would eradicate these. Also it would stop having to page through lots of data. The flip side is I wouldn't know how to retrieve the data from the print command back to Java.
So..
I currently don't have access to the SNA server but have some screen shots of what the terminal will look like once I get a connection and was therefore going to start work on parsing. With so many assumptions and not a lot of idea on what the data will look like I feel really stumped. Does anyone have any knowledge of these systems that might help me back on track?
You've picked a ripper of a problem there. 3270 is a very complex protocol indeed. I wouldn't bother about trying to implement it, it's a fool's errand, and I'm speaking from painful personal experience. Try to find a TN3270 (Telnet 3270) client API.
This might not specifically answer your question, but...
If you are using Rational Developer for z/OS, your java code should be able to use the integrated HATS product to deal with the 3270 stream. It might not fit your project, but I thought I would mention it if all you are trying to do is some simple screen scraping, it makes things very easy.