I have to implement the LPC (linear predictive coding) Algorithm with Java and quiet frankly don't have a clue where to start. Could someone please point me into a right direction.. I can't. of course, use already implemented algorithms from the java sound api (if its provides a solution).
Java comes with an AudioInputStream.
You can get the inputStream by calling avax.sound.sampled.AudioSystem.getAudioInputStream(File f).
The AudioInputStream has a read() method which reads the data. Probably, you will want to read all the data, do something with it and store it back to a file...
Related
I'm trying to record from the microphone to a wav file as per this example. At the same time, I need to be able to test for input level/volume and send an alert if it's too low. I've tried what's described in this link and seems to work ok.
The issue comes when trying to record and read bytes at the same time using one TargetDataLine (bytes read for monitoring are being skipped for recording and vice-versa.
Another thing is that these are long processes (hours probably) so memory usage should be considered.
How should I proceed here? Any way to clone TargetDataLine? Can I buffer a number of bytes while writing them with AudioSystem.write()? Is there any other way to write to a .wav file without filling the system memory?
Thanks!
If you are using a TargetDataLine for capturing audio similar to the example given in the Java Tutorials, then you have access to a byte array called "data". You can loop through this array to test the volume level before outputting it.
To do the volume testing, you will have to convert the bytes to some sort of sensible PCM data. For example, if the format is 16-bit stereo little-endian, you might take two bytes and assemble to either a signed short or a signed, normalized float, and then test.
I apologize for not looking more closely at your examples before posting my "solution".
I'm going to suggest that you extend InputStream, making a customized version that also performs the volume test. Override the 'read' method so that it obtains the byte that it returns from the code you have that tests the volume. You'll have to modify the volume-testing code to work on a per-byte basis and to pass through the required byte.
You should then be able to use this extended InputStream as an argument when you create the AudioInputStream for the output-to-wav stage.
I've used this approach to save audio successfully via two data sources: once from an array that is populated beforehand, once from a streaming audio mix passing through a "mixer" I wrote to combine audio data sources. The latter would be more like what you need to do. I haven't done it from a microphone source, though. But the same approach should work, as far as I can tell.
This is my understanding regarding reading a file using BufferedReader in java. Please correct me if I am wrong somewhere...
Recently I had a requirement where we are required to read a file multiple times.
The usual way which I use is setting a mark() and doing a reset. But the input parameters to
a mark is an integer and it cannot accept a long number. Is there a way in which we can read the file, a large number of times.
In c++ we can do a seekg on the fstream and read the contents once again irrespective of the number of times we want to do so. Is there anything in java which is of this nature.
Just close the file and read it again.
But review your requirement. Why can't you process it in one pass?
Not much of a good answer but if you want to do random reading and writing then you can use Channels in java.nio package.
BufferedReader is for reading a file when you logically see it as a series of records and records are generally accessed sequentially.
Channels allow you to view your file as a series of blocks. Blocks are meant to be read randomly. :)
Using subclass of channel, FileChannel, you can read what you want from wherever you want. You need to specify two things:
Where to read from.
How much to read.
It has a read(dst,pstn) where dst is a ByteBuffer and pstn is a long position.
Don't worry that it is abstract because you use it via Files.newByteChannel() which does all the voodoo needed to make it work :)
I understand, how to convert AudioInputStream from one format to another. Now, when I have stream converted, how to write it to matching SourceDataLine I have?
Just loop over read() and write() methods? Or there are better premade methods?
Yes. Usually done in a while loop with a boolean to allow a means of stopping via an "external" thread.
There is a good example in the Java Tutorials, under the heading "Using a SourceDataLine".
http://docs.oracle.com/javase/tutorial/sound/playing.html
There are extra steps for opening and closing the lines, but the tutorial covers this as well.
I'd like to modify the audio input stream, the stream that would come
from my microphone.
I have looked through the java.sound package API, but did not entirely understand it,
nor how to modify direct sound input.
Does anyone here know how to do that, or know an API that is capable of doing it?
You want a mixture of things:
The Java Sound system: http://www.oracle.com/technetwork/java/index-139508.html
A trail for it: http://docs.oracle.com/javase/tutorial/sound/index.html
Using audio controls: http://docs.oracle.com/javase/1.5.0/docs/guide/sound/programmer_guide/chapter6.html (part of a wider set of documentation)
If you are able to give more information about what you want to do to the audio stream, it's likely we'll be able to give you more specific advice.
Is there any open source Java implementation for LDPC (Low Density Parity Check) codes, I found only MATLAB codes.
My scenario is I will take text file and divide into block and I will delete some data in text file, and by using LDPC codes I need to recover data from text files.
Thanks.
I haven't tried this but the code here should get you started
http://www.cs.utoronto.ca/~radford/ftp/LDPC-2006-02-08/install.html
http://www.cs.utoronto.ca/~radford/ftp/LDPC-2006-02-08/examples.html
It's in C though. Might be easy to port. Or not.
I'd suggest looking into ways of calling matlab functions in java. I know there are a couple. Also why LDPC? While its one of the best FEC, it involves lots of matrix manipulation if I recall correctly. This is stuff much better suited for mat[rix]lab. The right tool for the right job...
There are also these two pure Java implementations:
https://github.com/a4a881d4/ldpc-java
https://github.com/pierroweb/LDPC-correcting-codes
I haven't tested them and would appreciate feedback from anyone else that has.
There's also a Java wrapper around a C++ library: http://cpham.perso.univ-pau.fr/MULTICAST/Java_wrapper_for_LDPC.html
Not the most promising results, but something to start from, at the very least.