I have to analyze bio acoustic audiofiles using matlab. Eventually I want to be able to find anomalies in the audio. That's the reason I need to find a way to represent the audio in a way I can extract and compare features. I'm dealing with mp3 files up to 150 mb. These files are too large for matlab to read in to it's memory. Therefore I want to use the memmapfile() function. I used the following code and a small mp3 file to find out how it actually works.
[testR, ~] = audioread('test.mp3');
testM = memmapfile('test.mp3');
disp(testM.Data);
disp(testR);
The actual values of the testM.Data and testR are different. Audioread() returns a 7483391 x 2 matrix and memmapfile() a 4113874 x 1 matrix.
I'm not really sure how memmapfile() works, I expected this to be equal to each other. Is there a way to read mp3 files in the same format audioread() does using memmapfile()? And what does memmapfile actually return in case of an audio file? Maybe it's also usable in the vector format in the case of anomaly detection?
Thanks in advance!
NOTE: The original files were in wav IMA ADPCM format with sizes from 1.5 up to 2.5 gb. Since Matlab can't deal with that format and the size of the files I converted them to 8bit mp3 files.
I think that the problem is mammapfile by default read data in uint8 format, while audioread function read data in another way.
How you can see here you can specify the format of data when you read it with memmapfile, so try to "play" with different values. From the documentation I read that you can read data in double format, so try to modify the memmapfile data format and audioread data format.
Last thing, memmapfile always organize the data in matrix like "somenumbers x 1", so if you want the original one you need to use something like reshape.
Anyway if you work with big data I suggest you to try with something different instead memmapfile, because it is very very slow
Related
I am using MATLAB tool for extracting silence part from audio WAV files. After extracting silence part from audio, I want to save new audio as a WAV file.
For this process, I use 'audiowrite' function. However, the program warns to me with this message :
Warning: Data clipped when writing file.
I tried to add 'BitsPerSample' value with single file format(32 bit) and I dont take a message from program with this way. I saved audio files with 32 bit but WAV files should be 16 bit.
How can I fix this problem?
audiowrite(filename,y,fs,'BitsPerSample',32);
Note: I also normalized data and problem is same.
Thanks for your help!
UPDATE:
I want to normalize audio samples as mean 0 and standard deviation or variance 1.Thus, I use z-score normalization technique.
Also,y/max(abs(y)) method is normalized data between -1 and 1. However, mean and variance are not equal to 0 and 1 respectively. These techniques are normalized data with different way.
Actually, My question is that How can I save samples with z score normalization technique without data clipping?
Matlab's audiowrite uses different normalizations for different data types. So if you want to get 16bit audio wav file, you should normalize your data to the [-32768,32767] range and convert your data to int16 type:
y_normalized = intmax('int16') * y/(max(abs(y))*1.001);
audiowrite(filename, int16(y_normalized), fs)
Similarly, for float you should normalize your data to the [-1,+1] range :
y_normalized = y/(max(abs(y)));
audiowrite(filename, y_normalized, fs)
My MATLAB script generates a figure from a timeseries data that, when saved, is over 200 MB in size. Is there a way to compress the figure to a lesser size in '*.fig' format? The compression has to be lossless so that I can zoom in and view the details in the figure. The figure has to be saved in *.fig format so that the axis property relations between subplots are preserved and I can use the data cursor tool.
The *.fig format cannot be saved as is in compressed form. The format is just not capable of it. But in MATLAB you can use functions zip to compress files created by savefig, and unzip with passing to openfig. This way you can create simple script to load and save zipped figs. Of course you will need to use a temp file, which should be taken care of as well.
I am currently working on watermarking audio files in Matlab for a mathematics research project. So far I have been able to read wav files using wavread in Matlab. However, because wav files are very large, the resulting data is also large. Therefore, in order to simplify this I would like to know how I would be able to read an mp3 file in Matlab. So far I have only tried to read an mp3 by using dsp.AudioFileReader. However, the resulting data only contains 0's and a few other numbers, which is clearly not the correct data. Would someone please be able to help me? Thank you so much!
you can use this code:
hfr = dsp.AudioFileReader('yourfile.mp3');
hplay = dsp.AudioPlayer('SampleRate',sample_rate_here);
while ~isDone(hfr)
audio = step(hfr);
step(hplay, audio);
end
I have a binary file with .bin extension. This file is created by a data acquisition software. Basically a "measurement computing" 16-bit data-acquisition hardware is receiving signals from a transducer(after amplified by an amplifier) and sending this to PC by a USB. A program/software then is generating a .bin file corresponding received serial data from data aq. hardware. There are several ways to read this .bin file and plot the signal in MATLAB.
When I open this .bin file with a hexeditor I can see the ASCII or ones and zeros (binary). The thing is I don't know how to interpret this knowledge. There are 208000 bytes in the file obtained in 16 seconds. I was thinking each 2 bytes corresponds to a sample since the DAQ device has 16 bit resolution. So I thought for example a 16-bit data such as 1000100111110010 is converted by MATLAB to a corresponding voltage level. But I tried to open two different .bin files with different voltage levels such as 1V and 9V and still teh numbers do not seem to be related what I think.
How does MATLAB read and interpret binary digits from a .bin file?
Thnx,
Assuming your .bin file is literally just a dump of the values recorded, you can read the data using fread (see the documentation for more info):
fid = fopen('path_to_your_file', 'r');
nSamples = 104000;
data = fread(fid, nSamples, 'int16');
fclose(fid);
You will also need to know, however, whether this data is signed or unsigned - if it's unsigned you can use 'uint16' as the third argument to fread instead. You should also find out if it's big-endian or little-endian... You should check the original program's source code.
It's a good idea to record the sample rate at which you make acquisitions like this, because you'll be hard pressed to do anything but trivial analysis on it afterwards without knowing this information. Often this kind of data is stored in .wav files, so that both the data and its sample rate (and the bit depth, in fact) are stored in the file. That way you don't need a separate bit of paper to go along with your file (also, reading .wav files in MATLAB is extremely easy).
I am working on a project that requires reading intensity values of several images from a text file that has 3 lines of file header, followed by each image. Each image consists of 15 lines of header followed by the intensity values that are arranged in 48 rows, where each row has 144 tab-delimited pixel values.
I have already created a .mat file to read these into Matlab and create a structure array for each image. I'd like to use OpenCV to track features in the image sequence.
Would it make more sense to create a .cpp file that will read the text file or use OpenCV and Matlab mex files in order to accomplish my goal?
I'd recommend writing C++ code to read the file directly independent of Matlab. This way, you don't have to mess with row major vs. column major ordering and all that jazz. Also, are there specs for the image format? If it turns out to be a reasonably common format, you may be able to find an off-the-self reader/library for it.
If you want the visualization and/or other image processing capabilities of Matlab, then mex file might be a reasonable approach.